United StatesDepartmentof Agriculture

Forest Service

IntermountainResearch Station

General TechnicalReport INT-GTR-35Revised

February 1995

ANATOMYOF A

MINEFROM

PROSPECTTO

PRODUCTION

Intermountain Research Station324 25th Street

Ogden, UT 84401

The use of trade or firm names in this publication is for reader information only,and does not imply endorsement by the U.S. Department of Agriculture of anyproduct or service.

This 1995 edition was funded by the ForestService’s Minerals and Geology Management Staff,Washington, DC. The combined efforts of Inter-mountain Region and Intermountain Research Sta-tion employees, and consultation with other ForestService Regions, in reviewing and updating thematerial brings to the reader the most currentminerals management information. We thank themall for their continued efforts to foster better under-standing of basic legislation, terminology, and pro-cesses used in the mining industry.

DENVER P. BURNSActing DirectorIntermountain Research Station

DALE N. BOSWORTHRegional ForesterIntermountain Region

AbstractReviews mining laws and regulations and their

application to mining in Western States. Describesprospecting, exploration, mine development andoperation, and reclamation factors.

Foreword“Anatomy of a Mine” was first prepared in looseleafform to aid Forest Service land managers andother administrators with mineral area responsi-bilities. The material summarized legislation af-fecting mining, defined mining terms, and dis-cussed basics of mineral exploration, develop-ment, and operation in the West. The goal then asnow was to foster better understanding and com-munication about minerals and forest and rangeland surface values.

The 1975 guide was written primarily by privatemining consultants James H. Bright and AnthonyL. Payne under direction of the Minerals and En-ergy Staff (now Minerals Area Management), In-termountain Region, Forest Service. It quicklybecame popular with land managers in many Stateand Federal agencies. Planners, environmental-ists, and mining industry personnel sought copies.Educators from elementary through college levelshave requested copies for classroom use.

In 1977, a revised publication was issued in thepresent format by the Intermountain ResearchStation, with funding and compilation provided bythe Surface Environment and Mining Program. Itwas updated for another edition in 1983. Nearly20,000 copies of the various editions have beendistributed, and demand continues. A major use ofthe publication is in training land managers.

ANATOMYOF A

MINEFROM

PROSPECTTO

PRODUCTION

PageFOREWARD ..................................................... iiINTRODUCTION............................................... 1MINING LAW .................................................... 3

Federal Laws ................................................. 3Claim Location ............................................ 4Lode vs. Placer Claims ............................... 5Extralateral Rights ...................................... 5Tunnel Sites ................................................ 5Mill Sites ..................................................... 6Claim Procedures ....................................... 6

Pursuit of Discovery ....................................... 7Protection Prior to Discovery ......................... 8Discovery ....................................................... 9Locatable Minerals ......................................... 9Leasable Minerals ........................................ 10Salable Minerals .......................................... 10Private Property ........................................... 11State Laws ................................................... 11Assessment Requirements .......................... 12Adverse Proceedings ................................... 14Rights of Claimants ...................................... 15Multiple Surface Use Act of 1955 ................ 16Occupancy ................................................... 16Trespass Limitations .................................... 17Federal and State Safety Requirements ...... 18Environmental Regulations .......................... 18Forest Service Regulations .......................... 18

PROSPECTING .............................................. 21The Conventional Prospector ...................... 22Amateur Prospectors ................................... 23Regional Mineral Exploration ....................... 23Exploration Concepts ................................... 24Preliminary Evaluation of Exploration Results 25

EXPLORATION............................................... 26Planning ....................................................... 27

Personnel ................................................. 27Access ...................................................... 27Occupancy ................................................ 27Communications ....................................... 28Property Adjustments ............................... 28Contact with Federal Agencies ................. 28

Geological Exploration Methods .................. 28Criteria for Ore Recognition ...................... 29

Geochemical Exploration Methods .............. 32Reconnaissance Geochemistry ................ 32Rocks ........................................................ 32Soils .......................................................... 33Vegetation ................................................ 35

Geophysical Exploration Methods................... 35Gravity ...................................................... 35Seismic ..................................................... 35Magnetic ................................................... 35

Electromagnetic ........................................ 36Electrical ................................................... 36Radiometric .............................................. 37Remote Sensing ....................................... 37

Restudy of Old Mining Districts .................... 38Trenches, Pits, Overburden Drilling ............. 39Exploration Drilling ....................................... 40

Hand Drilling ............................................. 41Percussion Drilling .................................... 41Rotary Drilling ........................................... 41Diamond Drilling ....................................... 42

Underground Exploration ............................. 43Bulk Sampling .............................................. 45Pilot Testing ................................................. 46Feasibility Studies ........................................ 46

DEVELOPMENT ............................................. 47Drilling Large Deposits ................................. 48Drilling Small Deposits ................................. 48Development Shafts and Adits .................... 49Blocking Out Ore Underground ................... 49

Proven (Measured) Ore ............................ 49Probable (Indicated) Ore .......................... 50Possible (Inferred) Ore ............................. 50

Access ......................................................... 50Power ........................................................... 51Communications .......................................... 51Site Preparation ........................................... 52

Mine .......................................................... 52Mill ............................................................ 53Town Site .................................................. 53

Postponement of Production ....................... 53PRODUCTION ................................................ 55

Underground Mining Methods ..................... 55Open Stoping ............................................ 55Shrinkage Stoping .................................... 55Cut and Fill Stoping .................................. 56Square-set Stoping ................................... 57Block Caving ............................................. 57

Surface Mining Methods .............................. 59Placer Mining ............................................ 59Glory Holing .............................................. 60Open Pit Mining ........................................ 61Leaching Methods .................................... 62

Ore Dressing ................................................ 63Crushing and Concentration ..................... 63Extractive Metallurgy ................................ 64

Wastes ......................................................... 65Mine Wastes ............................................. 65Mill Wastes ............................................... 66Miscellaneous Junk .................................. 67

Roads .......................................................... 67RECLAMATION .............................................. 68

CONTENTS

1

Western North America produces more metaland mineral products today than any other region ofsimilar size in the world. Beginning with the forty-niner’s discovery of gold, there has been one surgeof mining activity after another. Silver in the CivilWar era, copper at the turn of the century, potash,tungsten, phosphate, uranium, beryllium, to namebut a few, have gained importance in turn asdemand for metal and mineral products increasedand new advances in technology were made.

When contemplating the present mineralproduction of the western United States, it is difficultto imagine how undeveloped much of the regionmust have appeared to the early explorers. Thenatives had in their possession only a few trinketsof gold, silver, and copper, and seemed to have littleinterest in, or knowledge of, minerals. Thediscovery of placer gold at Sutter’s Mill at Coloma,California, in January of 1848 was the first of manyevents that revealed the importance of the richmineral resources of the West. The series of majornew mineral discoveries since the California goldrush seems paced almost as if the region weresome sort of gigantic mineral warehouse stockedwith new commodities for use as they becomeneeded.

Long gone are the days when mineral explorationconsisted of probing outcrops of bold gold and silverveins. The list of minerals required by industry todayincludes a majority of elements on the chemist’speriodic chart, and the variety of ore deposits in whichthey occur is so great that no one individual couldpossibly be competent to prospect for them all. Nogovernment specialist, academic authority, orcorporate expert is able to recognize the surfaceexpression of all ore types under all conditions.

The era of the legendary mining engineer, whocould go anywhere in the world and briskly size upthe ore potential of any kind of mineral property,passed during World War I. The method of themining engineer was to examine and sample thepartially developed ore deposits found by early goldand silver prospectors, to determine if other metalsmight be present, low grade ores might be profitablymined by mechanized methods and treated by oneof the efficient new metallurgical processes, or theproperty incorporated into a complex of mines, allshipping to a large, efficient, centralized smelter.

The modern explorationist goes back into areasinvestigated by the early prospectors and miningengineers, using new concepts of ore localizationand techniques of search for mineral deposits thatwould have been of no interest to his predecessors.In the early years of mining, there was no market formost of the metals mined today. Transportationwas inadequate, mechanized equipment andtechnology for development and treatment of theores were lacking, and major capital was notavailable for investment in large minedevelopments and surface plants.

The series of recent major discoveries ofpreviously unknown deposits of such materials asuranium, beryllium, potash, and gold makes it veryclear that the long-term prediction of future mineraldiscoveries is a most hazardous occupation. It isnot possible to determine that an area is lacking inmineral potential when the concept of the oredeposit containing it, the method of exploring for it,means of treatment, perhaps even the very use ofit are totally unknown today. Therefore, the mineralexplorationist views public land as a reserve ofpotential mineral resources in the very broadest

INTRODUCTION

2

sense. He sees his task as the efficient futureexploration and discovery of ore deposits ofsufficient number, size, and quality to becompetitively developed. In his view, the ultimatelogical extension of the idea that the Nation shouldwithdraw certain tracts of public land for specificlimited uses would require the reservation ofextensive areas for exploration and developmentof mineral resources.

Mineral values per acre may be immense in anygiven mineralized area These values, whetherknown or potential, should be considered carefullyin land use planning, particularly if withdrawalsfrom mineral exploration and development arecontemplated.

People within the mining industry have come toview with skepticism any suggestion for temporarywithdrawal of mineral entry in a given area, whereit is proposed that the land might later be openedto mining if the need becomes great enough. Theyreason that the lead time required to find, explore,and develop a prospect into a producing mine issuch that the only way to be sure of future miningoperations is to allow normal prospecting,exploration, and development over the widestpossible area. When poorly planned, hurried workis done in response to crisis. This results inexpensive exploration which is often notsuccessful in developing significant new mineralresources. Also, great damage to the surf aceenvironment may result.

Only a very small percentage of prospectsdevelop into producing mines; authoritativeestimates are in the range of 1 in 5,000 to 1 in10,000. The mineralized portions of the earth’scrust are at fixed localities, and it is not possible tomove the economic concentration of mineral to alocation where mining might conflict less with otherinterests.

Mining industry leaders believe that if the searchfor minerals continues over broad areas, adequatenew mineral resources can be found anddeveloped. If mineral exploration is severelyrestricted, confined to much smaller areas, or ifunreasonable burdens are placed on mining itselfmaking investment unattractive, they feel that thenumber of new mineral finds will dwindle, perhapsto the point of major damage to the economy andthe ability of the United States to provide for itself.

As an example of the unpredictable course ofmineral development, 25 years ago Government

authorities were seriously concerned because theUnited States lacked uranium ore, and the country’sability to defend itself and meet long-term energyneeds was in question. Incentives were offered foruranium production, and major discoveries suchas the Mi Vida deposit in Utah by independentgeologist Charles Steen motivated others, so thatwithin 10 years the Nation had developed thelargest, richest uranium ore reserves in the world.Uranium mining has grown to the point of beingsecond only to copper in economic importance inmetal mining west of the Rocky Mountains.

There will be more pressure on public lands toproduce minerals in the years to come. Manypartially developed nations are beginning to look totheir own future needs, and are no longer a source ofcheap, easily available, high quality mineral rawmaterials. Established mineral-producing countriesare becoming ever more nationalistic, and severalhave recently revised mining laws and imposed newtaxes upon mining operations that have slowed orstopped mineral exploration. Capital formerlyinvested in exploration in such areas is now beingdirected to more politically favorable regions such asthe western United States.

The increase in domestic demand for mineralsprogresses at an astonishing rate. More metal andmineral products have been used in the UnitedStates since World War II than were used in theentire previous history of the world, and demandincreases each year. The sale of metal, minerals,and competitive products manufactured from themcontinue to increase in importance as a source ofUnited States income overseas.

Society unquestionably derives major benefitsfrom mineral production. To emphasize onecommodity, the present major mining activity in theWest centers upon the copper mines of Arizona,New Mexico, Utah, Nevada, and Montana.Without these mines, copper could not beproduced in large quantities and at low cost,allowing its general use in mass production ofelectrical power, transportation, and otherconveniences enjoyed by everyone today. Similarbenefits could be cited in the case of other mineralssuch as lead, zinc, silver, gold, iron, coal, tungsten,and uranium. A healthy mining industry isimportant to the economy of the United States. Thefuture need for minerals cannot be expected todiminish unless there is a major turn downward inthe standard of living presently enjoyed in the

3

United States. There is no doubt that the potentialfor future discovery of major new mineral resourcesexists on public land.

Some mining people and resource managersthink that the present mining laws of the UnitedStates may soon be changed or modified.However, it should be noted that none of thelaws considered by Congress in recent yearscontemplate closure of public land to mining.

Mining has always been an authorized use ofmost National Forest land in the West. Thelanguage of the original legislation creating andauthorizing the National Forests set forth therights of a mineral locator as essentially thesame as those of a person who locates a claimon other public land. The rights of the mineralclaimant to explore and develop a valid claim onpublic lands open to mineral entry are clearlyrecognized.

MINING LAW

The body of mining law that authorizes andcontrols prospecting, claim procedures, leasing,development, and extraction of minerals on publiclands includes Federal and State laws, regulationsissued by administering agencies based upon thoselaws, and court decisions that have establishedprecedents for settling disputes. Rules establishedby organized mining districts, envisioned asimportant in early Federal law, have littlesignificance today. The organized districts havebeen gradually eliminated in most western States.

Federal LawsAcquisition of mining claims on public land is a

right granted by the United States Mining Law of1872. This law, passed by Congress on May 10,1872, continued a policy of opening mineral landsto exploration. The United States Mining Law of1872 expresses the general system of acquiringmining claims that was formed in California andNevada between 1848 and 1866. Until 1866 therewas a Federal policy of benign neglect with themineral claim system in use in the West.

A cornerstone of the early California Mining Lawwas that the discoverer obtained the right to hisdiscovery. The early day custom was that a claimdid not become property until mineral wasdiscovered and perfected by development. Thiswas the pattern for later law.

An 1866 mining law confirmed existing miningclaims and contained the declaration that theminerals on public land were open to explorationby all citizens of the United States. The locator wasgiven legal protection for his claim, and a systemwas devised by which a lode locator might acquiretitle by patenting. In 1870 the Placer Act amendedthe 1866 law to provide a method of patentingplacer claims. These several acts facilitated thedevelopment of mineral resources of the westernStates and territories.

In 1872 the Acts of 1868 and 1870 wererepassed by Congress as a single statute entitledthe United States Mining Law of 1872. Theacquisition of mining rights on large amounts ofpublic land in the West is, for the most part, stillgoverned by this law. The principal exceptions arethe Mineral Leasing Act of 1920, which made certainnonmetalliferous minerals exclusively leasable and

4

not open to acquisition by claim staking, theMaterials Act of 1947 that defined a group of salableminerals; the Multiple Mineral Use Act of 1954 thatprovided for multiple mineral development of thesame tracts of public lands; the Multiple SurfaceUse Mining Act of July 23, 1955, that withdrewcommon varieties from mineral entry; and a sectionof the Federal Land Policy and Management Act of1976 that redefines claim recording proceduresand provides for abandonment if the proceduresare not followed.

Claim LocationThe principal provisions of the 1872 statute are:

1. After discovery of a lode or vein, a miningclaim may be located on a plot of land notexceeding 1,500 feet in length along the lode orvein and 300 feet on each side of the middle ofsuch vein at the surface (fig. 1). Local miningdistrict rules or State laws may limit the width ofsuch claims to not less than 25 feet on each side

of the middle of the vein at the surface. Surfaceend lines must be parallel.

2. Upon completing the lode location, thelocator has the exclusive right of possession andenjoyment of all (a) surface included within thelines of the location for mining purposes; and (b)all veins, lodes, or ledges throughout their entiredepth if the top or apex lies inside of the surfacelines extended downward vertically, even thoughsuch veins may extend outside the vertical sidelines of the surface location.

3. Placer claims located by a single individualand based upon a single discovery are limited to20 acres. An association of individuals maylocate up to 160 acres on each discovery.

4. Both placer and lode locators are required toperform $100 worth of development work perclaim annually in order to hold their claims againstsubsequent locators.

5. There is provision for acquiring 5-acre claimsof nonmineral land for mill site purposes.

Figure 1.—Lode mining claim.

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6. The section commonly referred to as theTunnel Site Act gives an individual the right toprospect a maximum of 3,000 feet into a hillside,acquiring a prior right to all theretofore unknownveins and lodes cut by the tunnel; however, nosurface rights are attached.

The United States Mining Law of 1872 does notsanction the disposal or use of public lands forpurposes unrelated to mining.

Lode vs. Placer ClaimsThe mining location laws authorize two main

types of claims—lode and placer—depending onthe character of the deposit. Lode claims are stakedon veins or lodes of quartz or other rock in placebearing gold, silver, cinnabar, lead, tin, copper, orother valuable deposits. Placer claims are stakedon all forms of deposit, excepting veins of quartz, orother rock in place.

The locator must decide into which category hisdeposit falls and stake a lode or placer claim asappropriate.

In the United States Mining Law of 1872,Congress drew a distinction between the traditionalgold placer composed of alluvial material alongstream beds and the vein or lode found in solid rock.In many modern cases the choice is difficult asmany deposits do not clearly fall into eithercategory.

A lode is frequently considered as a zone or beltof mineralized rock clearly separated fromneighboring nonmineralized rock.

Placers are superficial deposits washed downfrom a vein or lode occupying the beds of ancientrivers, or deposits of valuable minerals found inparticles of alluvium in beds of active streams.

These definitions emphasize the present form ofthe deposit more than its origin, so that a depositbounded on either side by rock in place is likely tobe considered a lode. If the ore is on top of theground and has no cover except a thin veneer ofsoil, it is likely to be a placer. In the case of a disputethe courts tend to find in favor of the first locator.

A placer claim can be no larger than 20 acresfor an individual, with associations of up to eightpersons locating multiple claims of 20 acres perperson up to 160 acres. A placer location doesnot establish rights to any lodes within itsboundaries. Placer locations must conform asnearly as practicable to rectangular legal

subdivisions. All of the persons in an associationmust be active participants in the venture. Therights of a “dummy locator” may be invalid, if hefails to actively assert the rights of a principal inthe location. Corporations are considered to be asingle person. There is no limit to the number ofplacer claims that may be located by anindividual or association.

Extralateral RightsThe locator of a valid lode mining claim

acquires the right to mine all the veins and ledgesthroughout their entire depth, the tops or apexesof which lie inside of the claim surface lines (fig.2). Such veins or ledges may depart from aperpendicular in their course downward so as toextend outside vertical, downward extensions ofthe sidelines of the claim. Rights of the claimholder to mine the deposits after they leave thevertical claim lines underground are known ashis extralateral rights.

Extralateral rights apply only to lode claimswith parallel end lines and usually do not extendunder adjacent private land. Lawsuits overextralateral rights were very common at onetime, but today such disputes usually are settledprivately.

Tunnel SitesThe law provides for tunnel sites where a

horizontal excavation (adit) is made to discoverlodes and veins not appearing at the surface.The owners of such tunnels gain the right ofpossession of any previously unknown veins orlodes discovered along the 3,000-foot distancebetween the portal and face of the tunnel.

A tunnel site conveys no surface rights and theright of possession of a vein discovered in atunnel cannot be maintained unless the ownermakes a lode location of the vein on the surface.Discontinuing work for 6 months constitutesabandonment of a tunnel site.

A monument must be placed at the portal of thetunnel naming the locator, stating the proposeddirection of the tunnel, its height and width, andthe course and distance from the portal to apermanent object in the vicinity. The boundarylines of the tunnel site must be established bystakes placed along the 3,000-foot length of thetunnel line. Tunnel sites are uncommon today.

6

Mill SitesA 5-acre plot of nonmineral land may be staked

as a mill site. The land need not be contiguous to theclaim that will produce the ore for the mill. Mill sitesare monumented in the same manner as lodeclaims. No assessment work is required; but the millsite must be used for mining and milling purposes.

Claim ProceduresUnder the United States Mining Law of 1872, land

is claimed for minerals by distinctly marking thelocation on the ground so that its boundaries can bereadily traced and making a record of the name ornames of the locators, date of location, and adescription of the claim or claims located byreference to some natural object or permanentmonument that will identify the claim. In addition,State law requires the monumentation of claims bycorner posts, and in some cases, side and endcenter posts. A copy of a location notice must be

placed at the point of discovery and the locationnotice must be recorded with the recorder of thecounty in which the claim is situated. The FederalLand Policy and Management Act of 1976 requiresthat claim location documents also be filed withappropriate off ices of the Bureau of LandManagement.

Historically, mining claims have been marked orstaked in a variety of ways. Claim corners anddiscovery points have been marked on the groundby rock monuments or cairns, trimmed and blazedtrees, or iron posts embedded in soil, rock, orconcrete. The most common markers, however,are 4-by-4 wood posts.

It is essential that the discovery be made and thatthe location monument and notice be on public landopen to mineral entry, otherwise the entire claim isinvalid. Portions of a younger lode location mayoverlap older locations and claim boundarymonuments may be placed on land already claimed

Figure 2.—Extralateral rights of a lode mining claim.

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in order to square the claim or to take advantage ofan extralateral right not held in apex by previouslocators. The location monument is erected atsome point along the centerline inside the claim.Less than 300 feet on either side of the centerlineand less than 1,500 feet along the centerline maybe claimed, but the claim can never exceed 600 by1,500 feet in size.

All unappropriated Federal lands that have notbeen withdrawn from mineral entry are open tolocations of mining claims. Appropriated publiclands—those original public lands which arecovered by an entry, including mining claims, patentcertification, or other evidence of land disposal; orwhich are within a reservation, containimprovements constructed with Federal funds orare covered by certain classes of leases—are notopen to mineral entry. Lands covered by miningclaims validly maintained by another person are notsubject to location.

Mining claims can be located in Alaska,Arkansas, Arizona, California, Colorado, Florida,Idaho, Louisiana, Mississippi, Montana, Nebraska,Nevada, New Mexico, North Dakota, Oregon, SouthDakota, Utah, Washington, and Wyoming.

Land in National Monuments or National Parks,unless specifically authorized by law, Indianreservations, and acquired lands are not open forlocation. The claim locator must be a United Statescitizen or must have declared an intention tobecome a citizen. A domestic corporation isconsidered to be a citizen, regardless of thenationality of its stockholders. Employees of theDepartments of the Interior and Agriculture arerestricted in some ways from staking claims. Aminor competent to acquire and hold interests inland under State law is a qualified locator.

The 1872 law specifically requires discovery of avaluable mineral deposit within the limits of theclaim prior to locating a mining claim. Modern daymineral deposits are most often found at greatdepth and the actual discovery of mineral in placecommonly occurs in a drill hole after considerableexploration work. The prospector or geologist findsgeological, geophysical, or geochemicalindications of mineralization long before the drillingphase of the program encounters the discovery ofmineral in place.

Copies of the mining law and regulations in a formusable by prospectors, geologists, and Federalemployees can be obtained in Title 43 of Code ofFederal Regulations and in Title 30 of the U.S. CodeAnnotated. The pertinent portions of the 1872 law arepublished as a brochure by the U.S. Department ofInterior, Bureau of Land Management, entitledRegulations Pertaining to Mining Claims Under theGeneral Mining Laws of 1872, Multiple Use, andSpecial Disposal Provisions.

Pursuit of DiscoveryIn past years prospecting was limited to surface

outcrops where discovery was easily made withlimited equipment. Factors such as theever-increasing demands for new mineral resources,the economic incentives to produce minerals, andthe exhaustion of many known deposits make itnecessary to intensify the search for new mineraldeposits and to explore to considerable depthsbelow the ground surface.

Science and technology have provided newmethods, techniques, and instruments to aid inexploration. Mining companies have risked millionsof dollars in mineral exploration and research. Thishas trained and provided experience for mineralexplorationists in the art and science of ore finding.These advancements in ore finding capability opena new dimension not available to most prospectors.The old-fashioned prospector can find only whatcan be seen at the surface, and normally cannotafford the sophisticated methods used by themining companies.

Exploratory work is necessary, in many instances,to perfect a discovery. The general mining laws arepresently interpreted as extending an expressinvitation to enter upon the land and explore and,upon discovery, to claim by location with thepromise of full reward. The prospector who entersupon vacant public land, peacefully and in goodfaith, is not a trespasser, but is a licensee or a tenantat will. This right to enter is a statutory right. Amineral discovery cannot be made without the rightof entry and the time to explore.

Excavations are a necessary part of explorationfor minerals. This necessity to excavate is notnecessarily tantamount to removal and sale of the

8

excavated minerals. The prospector seeks only tomake a discovery by the use of such an excavation.In some cases it is necessary to sell extractedminerals to meet the marketability test of thevaluable mineral deposit.

Discovery of a valuable mineral deposit isessential in creating valid rights to a claim and inobtaining a patent.

Because the discovery is the foundation of title toa mining claim, discovery must be pursueddiligently by a bona fide claimant. Normally, to thelocator, the sequence of events is immaterial.Discovery may precede the location of a claim ormay follow the act of location; however, the actualtime of discovery is important in that it establishespriority between claimants and with theGovernment when there is conflict. Priority ofdiscovery gives priority of rights.

When two locators are in possession ofoverlapping claims before discovery, a racedevelops between the locators to make a discoveryfirst and the first discoverer obtains priority of rights.The rights of a locator actually begin on the date ofdiscovery of a valuable mineral deposit on a claim.This is true whether or not the required locationwork precedes or follows discovery. The need forsecrecy in a new discovery can be easily seen in acase of probable competition from a rival capable ofstaking conflicting claims. There is no substitute fordiscovery on a mining claim. Length of time heldand amount of money or effort consumed inworking on a claim does not dispense with the needfor discovery.

Where the issue of discovery is raised in acontroversy with the Federal Government, thefinding of small amounts of subeconomic mineral insufficient quantity to encourage or induce furtherprospecting and exploration is not sufficient for adiscovery. The actual mineral deposit must bedisclosed and available for sampling by somemeans. Geological inference or opinion, no matterhow strong, will not substitute for the actualexposure of mineral. Hope, belief, or expectationwill not sustain a discovery.

There must be physical exposure of valuablemineral in surface outcroppings, pits, shafts, or drillhole samples to demonstrate the discovery. Drillcore or cuttings will usually be accepted.

A lode discovery will not suffice for a placer claimnor will a pacer discovery suffice for a lode claim,and the discovery must be within the limits of theclaim.

Protection Prior toDiscovery

A person actively exploring a prospect desiresprotection against another locator on the land thathe is exploring, for the time necessary to discoverminerals in place.

The courts have recognized this problem andarrived at the doctrine of pedis possessio to provideprotection to the modern bona fide prospector.

Under the pedis possessio doctrine, a claimantwho has peacefully and in good faith staked claimsin search of valuable minerals, may exclusivelyhold the claims while he is diligently working againstothers having no better right than he, so long as heretains a continuous exclusive occupancy and ingood faith works toward making a discovery.During the period that the doctrine is operative in aparticular situation, the claimant must be activelyworking toward making a discovery by digging ordrilling. Making preparations for digging or drillingmay not be sufficient unless the preparatory activitydirectly precedes the actual digging or drilling.

Whether or not a prospector, geologist, or miningcompany can successfully assert rights of pedispossessio may vary in each particular case. Toclaim the rights there must be actual physicalpossession of all the ground, diligent bona fide workdirected toward making a discovery, and othersmust be excluded.

It is common exploration practice to locate a largeblock of claims over and around an area where it issuspected that deposits of valuable minerals mayoccur. The locator of such blocks is well advised tomaintain exclusive possession and to pursue adiscovery on each claim.

This possession or occupancy of the claims mustbe more than mere presence. Geophysical testingand geochemical work, unless followedimmediately by drilling, may not be sufficient.However, the requirement of physical occupancy isusually satisfied by work in progress. The exclusion

9

of others requires positive action. Rights are lost ifan adverse claimant is permitted to enter theproperty peacefully. Pedis possessio protectsagainst forcible entry. Thus it is necessary to denyentry to the intruding party.

If a confrontation occurs, and force is used by theentering party, the denial of entry need not besuccessful. The claimant or his agent simply yieldsto force, and then goes to his legal remedy. Theclaimant should make no statements indicatingconsent to trespass. In a land rush situation, a claimblock should be patrolled to deny entry to other thanauthorized public officials. Proposed new changesin the Federal mining laws provide for explorationclaims to cover a large area during the period priorto the discovery of valuable mineral in place. Thiscould remedy some of the shortcomings of the 1872Mining Law.

DiscoveryWhat is a discovery? The Federal statutes that

require discovery do not define the term, and thedefinition of discovery under the United StatesMining Law of 1872 continues to be a subject ofcontroversy. One basic standard for discovery hasbeen the prudent-man test, which states that therequirements of discovery have been met whenminerals have been found and there is evidencethat a person of ordinary prudence would bejustified in the further expenditure of labor andmoney, with a reasonable prospect of success indeveloping a valuable mine.

The test is not whether the individual claimantfeels he is justified in further expenditure, but whethera hypothetical “reasonable” man would be sojustified, and whether a profitable mining venture isprobable.

In 1933, the U.S. Department of the Interiorformulated the marketability test as a standard. Themarketability test states that the mineral locator orapplicant, to justify his possession of a location,must show by reason of accessibility, development,proximity to market, existence of present demand,and other factors that the deposit is of such valuethat it can be mined, removed, and disposed of ata profit.

The marketability test focuses on the economicvalue at the present time.

There continues to be a contest between theprudent man test and its extension — themarketability test. Every locator should beprepared to defend his discovery under thestandards of the marketability test. If a contestdevelops, the claim holder may be required to provemarketability in today’s market.

In considering these definitions of discovery,certain rules must be kept in mind. The depositdiscovered must be a valuable mineral deposit.This commonly means an assay or test of somekind must be made to determine the quantity andquality of metal or commodity in the discovery. Thesize of the deposit and the probable cost ofproduction are also considered.

The immediate effect of a valid discovery is toremove the land upon which the discovery hasbeen made from the unappropriated public lands.

The rules for determining what is a discovery ofvaluable mineral may vary according to the partiesand interests involved. The tests are quite differentin a contest between two adverse claimants thanthe tests used by the U.S. Government in a contestwith a claimant. The United States, by appropriatemethods, may question the validity of a claim at anytime and, in the absence of a discovery, mayterminate the prospector’s possession of aparticular claim by adjudication. The claimant,however may locate another claim on the generalsite, if he is acting in good faith.

Locatable MineralsWhatever is recognized as a valuable mineral by

standard authorities, whether metallic or othersubstance, when found on public land open tomineral entry in quality and quantity sufficient torender a claim valuable on account of the mineralcontent, is considered a locatable mineral underthe United States Mining Law of 1872. Specificallyexcluded from location are the leasable minerals,common varieties, and salable minerals describedin the next two sections.

Every valuable mineral deposit that is notexcluded by special legislation is a locatablemineral. The United States Mining Law of 1872specifically mentions rock in place bearing gold,silver, cinnabar, lead, tin, copper, or other valuabledeposits. As a general rule, all valuable metallicmineral deposits are locatable plus a large group of

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nonmetallic substances which have beendetermined to be locatable by either theDepartment of the Interior, a Federal or State court,or legislation by Congress. Some of the nonmetallicminerals in this group are borax, feldspar, fluorspar,and gypsum.

If a prospector, geologist, or land agencyrepresentative has any doubts about the locatableclassification of a mineral deposit, he shouldconsult a mineral expert on this point.

Leasable MineralsThe first major change in the United States

Mining Law of 1872 came with the passage of theMineral Leasing Act of 1920. Certain minerals werewithdrawn from location and were placed under theLeasing Act which provides for their developmentthrough prospecting permits and leases. Nopermanent rights are acquired from the U.S.Government, only the right to explore for and minethe specific minerals covered by the lease or permit.

The 1920 Act, as amended from time to time,places the following minerals under the leasing law:oil, gas, coal, oil shale, sodium, potassium,phosphate, native asphalt, solid or semisolidbitumen, bituminous rock, oil-impregnated rock orsand, and sulfur in Louisiana and New Mexico.

In general, to hold a lease, the miner is requiredto pay an annual rental in advance, to pay a royaltyto the Government on all material removed andsold, and to comply with any other provisionswritten into the lease.

The acquisition of mineral deposits by a leasefrom the Bureau of Land Management is verydifferent from the location of a valid claim on amineral discovery. Areas involved in leases arelarge compared to individual mining claimsbecause of the nature of the occurrence of leasableminerals. Filing fees and yearly land rental fees arecollected in advance, and bonds in varying amountsare required before the issuance of either aprospecting permit or a lease.

In areas in which leasable mineral deposits arenot known to occur, minerals can be leased by anoncompetitive procedure. In areas in whichleasable mineral deposits are known to occur inmarketable quantities, leases are issued to the

highest bidder, either by sealed bid or at publicauction. Leases issued in this manner are termedcompetitive leases. Regulations pertaining to theleasing of minerals other than oil and gas can beobtained in a Bureau of Land Management Circularor in Title 43 of the Code of Federal Regulations.

Public lands that passed from Federal ownershipthrough acts of Congress or disposal laws and werelater reacquired by the United States are known asacquired lands. Minerals subject to location onother lands must be leased on acquired lands.

The royalty rates for each lease are set by theU.S. Department of the Interior and may beobtained from BLM offices. For all minerals in thesame general area, royalties are usually the same.Royalties for the same minerals may be different invarious areas of the United States.

The Multiple Mineral Use Act of 1954 allows landthat is leased for one commodity to be claimed tocover minerals not in the leasable category. Insome cases this can be important where locatableminerals are found in an oil and gas lease area.

Salable MineralsThe Materials Act of 1947, as amended, removes

petrified wood, common varieties of sand, stone,gravel, pumice, pumicite, cinders, and some clayfrom location and leasing. These materials may beacquired by purchase only and are referred to assalable minerals.

Sales are handled through the agencyadministering the land upon the request of aninterested party or upon the request of anauthorized official. Sales are by competitivebidding if there is more than one interested party,otherwise a sale is negotiated by the authorizedofficer after the materials are appraised.

The sale of minerals does not limit the right ofthe U.S. Government to use the surface and toissue permits and licenses that do not interferewith the purchaser’s production of minerals. Theland must be reclaimed as required by the salecontract or by law when mining is completed.

A mining claimant risks prosecution fortrespass and may be liable for damages if heremoves salable materials from an unpatentedmining claim.

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Private PropertyIt is not uncommon for minerals beneath private

property to be owned by someone other than thesurface owner or by the Government.

Parcels of land that passed from the publicdomain into private ownership prior to the StockRaising Homestead Act of December 29, 1916,were classified as nonmineral and the minerals thatmight be under these lands passed to the feeowners of the surface. This 1916 Act eliminated anyproblems of mineral versus nonmineral lands byproviding for the reservation to the United States ofall minerals in every patent under this Act. Thus,most lands patented under the various homesteadacts from the public domain after 1916 are open tomineral entry under the United States Mining Law of1872.

There are many laws under which the original titleto land could be obtained, and it is necessary tocheck the document in the land records todetermine the law under which the title was granted.

Disposals under other laws both before and afterthe Stock Raising Homestead Act of 1916 oftenreserved minerals to the Government. TheSecretary of the Interior has never issuedregulations to dispose of these reserved minerals.

It is necessary for the miner to pay the privatesurface owner for damage to the surface caused byprospecting, mineral development, and mining. Thisis commonly done by arranging for a bond throughthe Bureau of Land Management as security fordamage to the surface, or by entering into acontract with the surface owner.

Sections 5 and 6 of the Taylor Grazing Act of June28, 1934, as amended, provided that the rights ofthe miner were not to be restricted in prospecting,locating, developing, mining, entering, or patentingunder applicable laws any mineral deposits foundon lands leased for grazing. The grazing leaseholder cannot restrict proper and lawful ingress oregress for prospecting purposes.

Minerals that are owned in fee simple by thesurface owner or that have been reserved in privateownership separately from the surface are not openfor prospecting, development, or mining withoutpermission from the owner. Normally, the mining

company attempts to obtain a lease with option topurchase from the owner.

State LawsThe United States Mining Law of 1872 did not

preempt the field, and State laws are permitted toelaborate on some aspects of mining law notcovered specifically by the Federal act.

State statutes deal primarily with locationprocedures, some aspects of assessmentrequirements, and the time method for filingdocuments. Most western States require posting ofthe notice of location on the land, which is notrequired by Federal law. The information requiredon the notice varies from State to State, andcontains substantially the same information as therecorded certificate.

Nearly all States require location work, althoughthe Federal law does not. Although location work isintended to disclose the evidence of discovery, itmay or may not result in a discovery. Location workis sometimes erroneously referred to as discoverywork.

All States require corner monuments. End-centerand side-center monuments may or may not berequired and the size and character of thesemonuments varies from State to State.

All records of unpatented mining claims are kept inthe county courthouse of the county in which theclaim is located. Under provisions of the FederalLand Policy and Management Act of 1976, similardocuments will have to be filed with appropriateBureau of Land Management offices.

When the United States Mining Law of 1872 waspassed, most western land was unsurveyed. In somewestern States there is still unsurveyed land. In manycases the descriptions of mining claims are so vaguethat they can properly be considered a floating claimblock. For unscrupulous claimants this type of claimblock may have the utilitarian value of being movedover any new discovery in the vicinity. The floatingclaim block can be moved anyplace that the claimantdesires by moving the claim posts and thus predateclaims made by the discoverer. It is normally possibleto contest such action, but the claimant may hold outfor a considerable cash payment for his nuisance

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value. Many attorneys will advise the major miningcompany to pay rather than fight, in order to get onwith exploration.

State mining laws in some cases require a mapfiled with the county recorder and perhaps apayment as well in lieu of location work. In Nevada,the county uses the payment to compile a masterclaim map, thus eliminating floating claims. Anyextra fee money provides an income to the countyfor general use.

Most mining legislation does not vary drasticallyfrom State to State; however, there is enoughvariation that an element of confusion anduncertainty pervades the State mining laws and aprospector or geologist must always carefullyexamine the law, particularly with reference tolocation and assessment procedures.

Assessment RequirementsThe annual labor or improvements required by

the United States Mining Law of 1872 on anunpatented claim is commonly referred to asassessment work. The general purpose of this workis to assure good faith and diligence and to preventa claimant from holding claims without working theground, thus preventing others from making entry.The pertinent provisions of the United StatesMining Law of 1872 require assessment work asfollows:

...On each claim located after the 10th day ofMay, 1872, and until a patent has been issuedtherefore, not less than $100 worth of labor shallbe performed or improvements made during eachyear...; but where such claims are held incommon, such expenditure may be made uponany one claim; and upon a failure to comply withthese conditions, the claim or mine upon whichsuch failure occurred shall be open to relocationin the same manner as if no location of the samehad ever been made, provided that the originallocators, their heirs, assigns, or legalrepresentatives have not resumed work upon theclaim after failure and before such location.... Theperiod within which the work required to be doneannually on all unpatented mineral claimslocated since May 10, 1872, shall commence at

12 o’clock meridian on the 1st day of Septembersucceeding the date of location of such claim....

By Act of February 11, 1875, the followingprovision was added to the United States MiningLaw of 1872:

...Where a person or company has or may run atunnel for the purposes of developing a lode orlodes, owned by said person or company, themoney so expended in said tunnel shall be takenand considered as expended on said lode orlodes, whether located prior to or since May 10,1872; and such person or company shall not berequired to perform work on the surface of saidlode or lodes in order to hold the same as requiredby this section....

The most recent Federal legislation was enactedon September 2, 1958, and provides:

...The term labor, as used in the third sentence ofsection 2324 of the Revised Statutes (30 U.S.C.28), shall include, without being limited to,geological, geochemical and geophysicalsurveys conducted by qualified experts andverified by a detailed report filed in the countyoffice in which the claim is located which setsforth fully (a) the location of the work performed inrelation to the point of discovery and boundariesof the claim, (b) the nature, extent, and costthereof, (c) the basic findings therefrom, and (d)the name, address, and professional backgroundof the person or persons conducting the work.Such surveys, however, may not be applied aslabor for more than two consecutive years or formore than a total of five years on any one miningclaim, and each survey shall be nonrepetitive ofany previous survey on the same claim....

The regulations as stated in Title 43 of the Codeof Federal Regulations, provide that:

(a) The term geological surveys meanssurveys on the ground for mineral deposits bythe proper application of the principles andtechniques of the science of geology as theyrelate to the search for and discovery ofmineral deposits;

(b) The term geochemical surveys meanssurveys on the ground for mineral deposits by theproper application of the principles and

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techniques of the science of chemistry as theyrelate to the search for and discovery of mineraldeposits;

(c) The term geophysical surveys meanssurveys on the ground for mineral deposits throughthe employment of generally recognizedequipment and methods for measuring physicaldifferences between rock types or discontinuitiesin geological formations; and

(d) The term qualified expert means anindividual qualified by education or experience toconduct geological, geochemical or geophysicalsurveys, as the case may be.

In most States, filing of proof of labor in thecounty records is required by State law within alimited time period.

The question of what can qual i fy forassessment work is not always easy to answer.It is necessary to remember that it is $100 worthof labor and improvements. The work must havea value of $100, not necessarily cost $100.Geological, geochemical, and geophysicalsurveys, some road work, tunneling, digging pits,cuts or trenches, or excavations, and drillingwhich tends to develop the mineral deposit qualifyas assessment work. The intent is to inducedevelopment of minerals and to avoidspeculat ive holding of claims. Casualprospecting or surface sampling for the purposeof making a discovery will not serve asassessment work.

Over the years the courts have generallyprescribed rules governing the character of thework and improvements that will satisfy theassessment work requirement. The court rulingshave been lengthy and complex, but they can besummarized as fol lows: the labor andimprovements, within the meaning of the statute,should be deemed to be done when the labor isperformed or improvements made for thepurpose of working, prospecting, or developingthe mining ground embraced in the location, orfor the purpose of facilitating the extraction orremoval of ore.

Claims may be grouped for assessment workpurposes. That is, work can be done on one ormore claims rather than on each claim in a group,and the assessment work requirements can bemet if the value of the work is sufficient. The

claims must be contiguous, that is, overlap orshare common sidelines, and there must be acommunity of interest if more than one claimowner is involved. There are no rules thatcompletely cover the grouping of claims. Thecircumstances in each case can be important.

As a practical matter, many claim holders dolittle or no assessment work on their claims andfile questionable proof of labor statements. Insome circumstances this may constitute perjury.

If there is a contest over the performance ofassessment work, the burden of proof concerning theperformance generally is on the party contending thatthe required work was not done. As a general rule, incourt cases where a second locator attempts torelocate the claim of the original locator who hasallegedly failed to perform the required assessmentwork, most decisions tend to protect the originallocator where it appears that he has acted in goodfaith. The courts generally do not substitute theirjudgment for that of the miner if the work tends todevelop the claim and facilitate the extraction of ore.

The absence of an assessment work affidavitin the county records may encourage a newclaimant interested in the ground to locate newclaims. The failure by the original locator to filethe proof of labor forms does not verify that therequired annual work was not done. If the originallocator can prove that the necessaryassessment work was done, he retains rights ofpossession under Federal law.

To the prospector or independent geologist,traveling to numerous claim groups andperforming assessment work can be an onerousand expensive task. Most mining companies withlarge claim holdings maintain a system of recordsin the company files and assign one man for partor all of the year to keep track of assessmentwork and see that it is properly recorded. TheGovernment may under certain circumstancesinvalidate a claim where assessment work hasnot been performed.

Effective August in, 1993, legislation wasenacted that affected the requirements ofrecordation of new mining claim locations orsites and annual assessment requirements. Thenew requirements can be found in 43 CFR Part3830 - Location of mining claims. The reader isadvised to contact the local Bureau of LandManagement office for further information.

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State law requirements are still to be followed.The claimant should consult with the State for theserequirements.

Adverse ProceedingsThe problems of adverse claimants can fall under

two general categories:1. A contest between two private citizens or

companies over ownership of mining claims.2. A legal action initiated by the U.S. Government

against a mining claim held by a private citizen orcorporate claimant.

In past years there was much litigation overextralateral rights, where a vein apexed (fig. 2) onone claim and extended down-dip off the claim.This type of litigation was commonly bitter andcostly to settle. Extralateral rights litigation betweentwo adverse claimants is now uncommon, asnegotiated settlements are more satisfactory thandrawn-out expensive lawsuits.

Occasionally, two exploration groups may decideat approximately the same time to stake a largeblock of claims over a target area where explorationwill be required to make a discovery. One groupmay begin staking claims first and the second groupmay stake from the other end of the area, possiblynot knowing of the competitor’s activity, and a“staking rush” is on when either or both of theparties discover the other’s activities.

As they become aware of each other’s activities,the doctrine of pedis possessio (see ProtectionPrior to Discovery section) will come into use. Onegroup may attempt to deny peaceful intrusion ontoits claims by the other group. An adverse claimantsituation often exists between the two groups. Thekey to the situation now depends on who can makea discovery first, usually by drilling. Many complexlegal problems may develop as the claimants raceto be the first to make a discovery.

About this time, it is possible that a group offloating older claims in the district will be movedunder the claims covering the new discovery area.There is also the possibility that placer claims will bestaked by unscrupulous individuals over thediscovery area in the hope that the major miningcompany will buy out the nuisance value of theplacer claims rather than fight in court. Sometimes

the mining company’s counsel will mistakenlyadvise a payoff; each time this is done it onlycompounds future difficulties.

There may be circumstances where a group ofclaims will appear to be abandoned. A search ofthe county records fails to reveal an assessmentaffidavit for the immediate past assessment yearending at noon on September 1. Inspection of theground reveals no recent physical work of thekind required for assessment. Under thesecircumstances, a new set of claims may be stakedon what appears to be open ground. The newclaimant does the required location work andbegins exploration—pursuit of discovery—on theclaim group.

If the former claimant has in fact abandonedthe claims there will be no problems; however, ifthe former claimant had no intention ofabandoning the ground there may be a legalcontest over who has the best claim to the ground.If the original claimant has filed his proof of labor,the new claimant would have to prove that theassessment work had not been done. Not havingfiled the proof of labor, the original claimant nowmay be in the position of having to prove that heperformed the required assessment work.

Claims staked for leasable or salableminerals are subject to adverse action by theU.S. Government. The claimant is in trespassand may end up paying for the minerals thathave been illegally removed. It is possible tolocate legal mineral claims covering the sameground where the U.S. Government has leasedor sold the nonlocatable minerals. No title isobtained to the nonlocatable minerals andtheir production cannot be impeded by thelocator.

Many cases of unauthorized occupancy havecaused the Government to initiate an action toremove a home or cabin or to correct someother nonmineral use.

Some claimants locate claims on land that isnot open for mineral entry. This is often donewhere the locator believes the claims to be in adifferent section of land than they actually are.This may be a surveying problem, or the claimantmay have failed to make the necessary check ofthe land management agency records todetermine the status of the land.

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Congress has given the Department of theInterior adjudicative powers in matters relating tothe mining laws. The most common action is acontest of claim validity conducted under theregulations of the U.S. Department of Interior. TheDepartment of the Interior’s authority in this areahas been confirmed by the U.S. Supreme Court.The administering agency can initiate a complaintwhich will result in a contest through theDepartment of Interior under the AdministrativeProcedures Act for a variety of reasons, includinglack of discovery. Necessary action may beinitiated simultaneously in the Federal Courts toresolve urgent conflicts. After proceeding throughthe Department of the Interior regulations process,the contest may go to the U.S. District Court withappeals to the Circuit Court or Supreme Court.Where the contest is of great magnitude,considerable time, money, and effort can beexpended in actions of this type.

At the time of application for patent, there is a60-day period when adverse claims can be filedwith the office where the patent application wasinitiated. An adverse claim may be brought byanother claimant who can demonstrate a right to allor a portion of the claim being patented. There isalso an opportunity for persons in the vicinity of amining claim to protest that the patent applicant hasnot met the mining law requirements. Protestsagainst a patent can be filed by the Forest Serviceat any time before patent for noncompliance withdiscovery or labor requirements.

Rights of ClaimantsUnder the United States Mining Law of 1872, the

locator of a valid mining claim that has beenperfected by the discovery of a presentlymarketable mineral deposit and by the performanceof all the required acts of location acquires theexclusive right of possession and enjoyment of allof the locatable minerals within the boundaries ofhis location. He also acquires any appropriateextralateral rights along with the use of the surfacecompatible with the Multiple Surface Use Act of1955.

Prior to the discovery of a presently marketablemineral deposit within the claims boundary, theclaimant has a questionable title to the claim.Prediscovery rights can be held against an adverse

claimant under the doctrine of pedis possessioby actively pursuing discovery and maintainingcontinuous exclusive occupancy. This doctrineprovides only tenuous prediscovery protectionand it is not possible to generalize as to whataction will satisfy the requirements in all cases;litigation my often result.

The claim locator has the right to prospect,develop the mineral potential, do assessmentwork, and perform other acts related toexploration that are not forbidden by law orregulation.

Where there are conflicting or overlappingclaims, most rights are determined on the basisof priority of discovery, but subsurface rights arenot necessarily so determined. Extralateral rightsto a vein are based on apex considerations.

Valid, unpatented mining claims are realproperty in the full sense of the term, except asmodified by multiple use legislation. When allrequirements have been met, the locator has avalid, marketable title for mining purposes. Aslong as the locator complies with Federal andlocal laws and regulations in good faith, he haspossessory title segregated from the public lands,although the paramount title remains in the U.S.Government until a patent is granted. Thispossessory title may be maintained indefinitelyas long as the appropriate laws are compliedwith. This title does not include timber except asused for mining purposes on the claim, nor theright to nonmining use of the surface.Assessment work must be done on the claim inthe amount of $100 per claim for eachassessment year to maintain the possessorytitle. The assessment year begins at noon onSeptember 1 of each year.

A claim locator who does not performassessment work for a period may resume such workat any time, in the absence of the intervening rights ofan adverse claimant on the ground. The original claimlocator regains the same rights and title he obtainedby locating the original claim, providing that he candemonstrate the existence of a valuable deposit of alocatable mineral.

The U.S. Government may initiate a contest usingthe Bureau of Land Management adverse claimprocedures for cause affecting the legality of a miningclaim. The procedure is set forth in the Federalstatutes as supplemented by Departmentregulations.

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In a mineral contest between the Governmentand a claimant the Government is required topresent prima facie evidence (evidence sufficient toraise a presumption of fact or establish the fact inquestion unless rebutted) that the claim is invalid.The claimant has the right to retain expertassistance in defending his position and must showby a preponderance of evidence that his claim isvalid.

In actual practice, the average claimant has notmade a valid discovery prior to locating his claim.Many claimants mistakenly believe thatcompliance with State location laws fulfills theFederal requirement of discovery. It is common fora claimant to refer to having done the discoverywork on a claim when in actual fact he has done theState-required location work.

Under the Multiple Surface Use Act of July 23,1955, prior to the issuance of a patent the UnitedStates and its licensees have the right to use asmuch of the surface and surface resources as isnecessary for access to adjacent land, providingthat this use does not interfere with prospecting,mining, or processing. The claimant does not havethe right to use an unpatented mining claim forpurposes other than prospecting, mining, orprocessing operations and uses reasonablyincident thereto. In the interpretation of what is“reasonably incident thereto,” there are gray areassubject to various interpretations.

The claimant has the optional right to apply for apatent. The conditions that must be met prior tofiling an application are: a valid discovery of avaluable mineral deposit, the performance of $500worth of improvements which directly facilitate thedevelopment of the mineral deposit, and thepreparation of survey plat and field notes by aDeputy U.S. Mineral Surveyor. If the patentapplication is successful, the claimant must pay forthe land at the rate of $5 per acre for a lode claimand $2.50 per acre for a placer claim. After patent,the surface and minerals on the claim are privateland subject to local property taxation, and theannual assessment work is no longer required.

Multiple Surface Use Actof 1955

Congress enacted the Multiple Surface Use Actin 1955 to curtail nonmining use of the surface of

mining claims. Under the Act any mining claimlocated after July 23, 1955, shall not be used priorto the issuance of patent for any purposes otherthan prospecting, mining, or processing operationsand uses reasonably incident thereto. The rights ofthe holder of a claim staked after July 23, 1955, andprior to patent are subject to the right of the UnitedStates to manage and dispose of the vegetativesurface resources and to manage other surfaceresources, except the locatable mineral depositson the claim.

The Act also provides that mining claims will be,prior to issuance of a patent, subject to the right ofthe Government to use so much of the surface asmay be necessary for access to adjacent land. Anyuse of the surface of the mining claim by theGovernment must not endanger or materiallyinterfere with prospecting, mining, or processingoperations or uses reasonably incident thereto.

The holder of a valid mining claim is stillauthorized to cut and use timber from the claim formining purposes.

The result of this legislation is that the owner of amining claim is entitled to use the surface only asnecessary for the mining operation, and the claimsare subject to surface management by the FederalGovernment until patented.

OccupancyThe mining laws permit a claimant to makereasonable use of the claim surface area prior to apatent being granted, so long as this use isconnected with mining. The mining laws do notpermit the use of an unpatented mining claim forland on which to build a home or cabin. There havebeen many cases where persons unfamiliar withthe mining laws have built homes or cabins onclaims staked with this idea in mind, or purchasedas cabin sites.

The Mining Claims Occupancy Act passed byCongress in October 1962 enabled people makingtheir principal residence on an improved site on amining claim to occupy the land which theresidence occupied. The law was extended untilJune 30, 1971.

Buildings necessary for mining facilities areallowed on valid mining claims when discovery isnot an issue. It is often necessary to erect buildingson unpatented mining claims to protect equipment,store samples, or house personnel.

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In dealing with unauthorized occupancy there iscommonly a question of what is authorized use formining purposes. Even if the claim is valid, theoccupancy may exceed that needed for miningpurposes. Some habitation of buildings can verywell be an authorized use. The administering agencyshould obtain a technical opinion regarding theclaim validity before questioning possibleunauthorized occupancy.

Trespass LimitationsThe owner of an unpatented mining claim has

only limited rights to prevent trespass. He does notnecessarily have the right to fence the claim anderect no trespass notices. Under the MultipleSurface Use Act, the surface may be used fornonmining purposes such as hunting and fishing bypersons other than the claim holder.

After a valid discovery of valuable mineral hasbeen made, the claimed area is no longerunappropriated public land. The intent of the law isthat the same ground cannot be located orpossessed by another claimant until such time asthe claim is abandoned by the original claimant.

Active mining operations obviously have a right toforbid trespass in and around buildings, mineworkings, and mills. For this purpose, fences andno trespassing signs are commonly erected.

Trespass on mining claims may be an accident orinnocent mistake, intentional and justifiable, orintentional and not justifiable, and may becommitted on the surface or underground. Aperson entering within the sidelines of anotherminer’s lode claim for the purpose of mining is atrespasser if the vein being mined apexes (see fig.2) on the miner’s claim. The corner monuments ofadjacent claims may be placed on the surface ofadjacent unpatented or patented mining propertyfor the purposes of squaring the located claim. Theconsent of the owner is not essential when theencroachment is open and peacefully done. Theright of the overlapping locator is limited to theground outside of the prior located claim orpatented ground, except for extralateral rights thatmight be acquired. Subsequent objection by theprior owner is unavailing.

Prior to the Multiple Surface Use Mining Act ofJuly 23, 1955, claimants commonly took quite

literally the statement in the United States MiningLaw of 1872 that the locator acquired the exclusiveright of possession and enjoyment of all the surfaceincluded within the lines of his location. Minerscommonly clear t imber on a claim fordevelopment purposes, used it in surfacestructures and in underground workings, andsometimes sold the timber outright. Prior to 1955,the miner had no right to sell the timber except forclearance, nor could the Government remove orsell the timber on a claim except in the case of anemergency or insect infestation. In 1955,Congress enacted the Multiple Surface Use Actto curtail nonmining use of the surface of miningclaims. While the locator’s possession andenjoyment is exclusive for mining purposes, theGovernment and its licensees may, under propercircumstances, exercise rights of way across theclaim so long as in so doing they do not interferewith the mineral development of the claim.

On an inactive mining claim no trespass iscommitted by people passing through the areahiking, hunting, rock collecting, fishing, or fornumerous other reasons. Prospectors andgeologists may examine the showing on a claimwithout prior knowledge of its status as a miningclaim or what the ownership is. It is commonpractice to examine mineral showings and quicklymap and sample the surface and undergroundgeology of a prospect without contacting theowner of a claim. If a prospector or geologistspent the time necessary to contact all absenteeowners prior to examining all prospects moretime would be spent trying to find people than inlooking for ore. This type of examination is oftento the advantage of the absentee claim owner,for if something of interest is found in theexamination the owner will be contacted. Ifnothing is found he is not bothered unnecessarily.

If the owner of a valid mining claim is workingthe claim it is the usual custom for the prospectoror geologist to stop and talk, and to gainpermission to look around.

There is an occasional hermit or recluse whodoes not want anyone to come near hisworkings, let alone examine the geology orsample the showings. Unless the showings areof unusual meri t the prospect wi l l goundeveloped while such an individual is inpossession of the claims.

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Federal and State SafetyRequirements

The conditions of safety around a developing oroperating mine are controlled by both Federal andState laws. The mining States have State mineinspection organizations that inspect and advise onthe physical condition of an operation.

On the Federal level, two safety inspectionorganizations exist. These are Mine Safety andHealth Administration (MSHA), an agency of theU.S. Department of Labor, and Occupational Safetyand Health Administration (OSHA), also an agencyof the U.S. Department of Labor. These agencieshave prepared pamphlets explaining theirfunctions.

The activities of MSHA and some State mineinspection organizations overlap and somecoordination exists where the State group hasagreed to Federal standards. All three groups keeprecords and investigate serious accidents andfatalities at mine operations.

The Bureau of Mines has a safety demonstrationgroup, operating out of Boulder City, Nevada, whichresearches and devises safer methods forperforming various tasks.

Most western States have laws requiring thatshafts, drill holes, tunnels, and small pits becovered or fenced where they can be a danger tolife.

EnvironmentalRegulations

The National Environmental Policy Act of 1969,as interpreted by the courts and implemented in theregulations of the various involved agencies, hasadded an important dimension to the preparation ofplans for exploration and development of resourceson the public lands.

An Environmental Impact Statement is notrequired for every transaction involving resourcedevelopment. It is possible to prepare a negativedeclaration when, based on an impact appraisal, nosignificant impact is anticipated. A nominal impactdeclaration is also possible. Proper authorities must

concur. If National Forest lands are involved, thenew regulations apply (Mineral Resources onNational Forests Use Under U.S. Mining Laws, Title36, Code of Federal Regulations, Part 228).

All mine development programs on public landmust comply with appropriate regulations.

At the earliest possible time, the manager of anexploration project with the potential for developinginto a producing mine should begin keeping anenvironmental analysis record of the condition ofthe air and the water in any stream or lakes on ornear the project, the condition of trees andvegetation, and any wildlife disturbance resultingfrom the project. This environmental baseline datamay prove essential in demonstrating whatenvironmental changes occur, if any, as the resultof the mining operation.

Environmental analysis and the preparation ofthe required statements, plans, reports, andfollowing correct, established procedures is acomplicated task which usually should be done byexperts. In most cases, a mining company bringinga new mine into production employs full-timepersonal or consultants to do a complete job ofenvironmental analysis. In the case of the smalloperator, where the project will not financiallysupport expert help, the best plan is to obtain thenecessary information from the proper authoritiesprior to preparing a statement for submittal.

The Mining and Minerals Policy Act of 1970declares that it is the continuing policy of theFederal Government in the national interest tofoster and encourage private enterprise in thedevelopment of an economically sound and stabledomestic mining industry, the orderly andeconomic development of domestic resources andreserves, and the reclamation of metals andminerals to help assure the fulfillment of industrial,environmental, and security needs.

Forest ServiceRegulations

Forest Service Regulations, 36 CFR 228, providefor a minimum adverse environmental impact onthe National Forest System surface resources frommining operations.

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To minimize surface resource impact on miningclaims, the regulations require that an operator whois conducting prospecting, exploration,development, mining, or processing of mineralresources in a National Forest file a notice of intentor plan of operations when the proposed work maycause a significant disturbance of the surfaceresources.

The notice of intent is submitted to the DistrictRanger for determination of significant disturbanceof the surface resources. If significant disturbancewill result, in the opinion of the District Ranger, theoperator is required to submit a proposed plan ofoperations.

A notice of intent and a plan of operations neednot be submitted for prospecting operations thatuse existing roads and occasionally remove samplesin a manner that will not cause significant surfacedisturbance. Claim staking subsurface operations,and work that does not disturb vegetation or usemechanical earthmoving equipment are exemptfrom the notice requirements under the regulations.The notice of intent to operate must provide enoughinformation to identify the area involved, the natureof the proposed operations, the route of access,and the method of transport. The District Rangermust notify the operator within 15 days if a plan ofoperations is required.

The notice of intent may be bypassed by filing aplan of operations when the operator is certain thathis operations will cause a significant surfacedisturbance.

The plan of operations must include:1. The name and legal mailing address of the

operator (and claimants if they are not theoperators) and their lessees, assigns, ordesignees.

2. A map or sketch showing information sufficientto locate the proposed area of operations on theground, existing and proposed roads or accessroutes to be used in connection with the operationsas set forth in the regulations, and the approximatelocation and size of areas where surface resourceswill be disturbed.

3. Information sufficient to describe or identify thetype of operations proposed and how they would beconducted, the type and standard of existing andproposed roads or access routes, the means oftransportation used or to be used, the period during

which the proposed activity will take place, andmeasures to be taken to meet the requirements forenvironmental protection.

The plan of operations must cover therequirements reasonably foreseen for theoperation for the full estimated period of activity.Whenever the operator proposes operations notforeseen in the initial plan, he must file asupplemental plan or plans.

Approval must be obtained of a proposal to buildan access road to the project area to begin anyplanned operations. Without reasonable access,many exploration projects are not viable.Exploration activity in the National Forests can bedelayed by requirements imposed under theNational Environmental Policy Act.

After the Forest Service completes anenvironmental analysis in connection with eachproposed operating plan, the Forest Service officerwill determine whether an environmental statementis required. Not every plan of operations,supplemental plan, or modification will involve thepreparation of an environmental statement.Environmental impacts will vary substantiallydepending on whether the nature of operations isprospecting, exploration, development, orprocessing, and on the scope of operations (suchas size of operations, construction required, lengthof operations, and equipment required) resulting invarying degrees of disturbance to vegetativeresources, soil, water, air, or wildlife. The ForestService will prepare any environmental statementsthat may be required.

When the District Ranger receives the proposedplan of operations he must promptly acknowledgeits receipt.

The authorized officer must make anenvironmental analysis within 30 days and:

1. Notify the operator that he has approved theplan of operations, or

2. Notify the operator that the proposedoperations are such as not to require an operatingplan; or

3. Notify the operator of any changes in, or addi-tions to, the plan of operations deemednecessary to meet the purpose of the regulations; or

4. Notify the operator that the plan is beingreviewed, but that more time, not to exceed anadditional 60 days, is necessary to complete the

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review, setting forth the reasons why additionaltime is needed. Provided, however, that daysduring which the area of operations is inaccessiblefor inspection shall not be included whencomputing the 60-day period; or

5. Notify the operator that the plan cannot beapproved until a final environmental statement hasbeen prepared and filed with the Council onEnvironmental Quality.

New regulations dated November 4, 1993 (36CFR Part 215) supersede the time frames forapproval of operating plans under 36 CFR 228(A).

After an operation begins, the Forest Service hasthe right to inspect the operation and issue noticesof noncompliance with the plan. Noncompliancenotices must indicate what is needed to correct theproblems identified.

Some considerations in environmentalprotection are: air, water, solid wastes, scenicvalues, fish and wildlife habitat, roads, reclamation,erosion, landslides, water runoff, control of toxicmaterials, reshaping and revegetation of disturbedareas, and rehabilitation of fish and wildlife habitatwhen the operation is completed.

After the operation ceases permanently, the sitemust be cleaned up within a reasonable time. Thismay include removing equipment and structures orother facilities.

When a plan of operations is filed, a bond may berequired assuring that reclamation is completed inaccordance with the plan of operations.

While awaiting approval of the plan of operationsthe authorized officer will approve the work neededto perform assessment requirements.

During operations under an approved plan, theauthorized officer may request a modification tominimize unforeseen significant disturbances. TheForest Service may be required to suggest

reasonable means of correcting the problem. TheForest Service may attempt to close down anoperation that is causing irreparable andunnecessary injury to the surface resources.

The Forest Service will arrange for consultationwith the Geological Survey and the Bureau of Minesor other appropriate U.S. Department of Interioragencies on significant technical questions ofgeology, development systems, techniques, andequipment. The operator may request this type ofconsultation.

All of the information will be available forexamination by the public, except for informationand data designated as confidential by theoperator. Confidential information might includetrade secrets, privileged financial andcommercial information such as the known or esti-mated outline of a mineral deposit and its exactlocation, the details of an exploration project, andother competitive commercial information.

An operator aggrieved by a decision of anauthorized officer may file an administrativeappeal through the Forest Service appealsystem set out in the regulations. Appealsbeyond the prescribed system should go throughthe appropriate courts.

The regulations are applicable in Wilderness andPrimitive Areas as long as the mining laws apply inthese areas.

These regulations are a part of a vigorousprogram to minimize surface damage frommining in the National Forests. Care will be takenthat the regulations are not unreasonably used torestrict the statutory right that the miner has toprospect for, and develop, minerals in public landsopen to entry.

The regulations are in Title 36, Code of FederalRegulations. A question and answer pamphlet onthis subject has been prepared by the Forest Service.

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The role of the small prospector-miner has beensomewhat distorted by romanticists, who glossover the complex series of steps necessary to takea prospect into production. Perhaps only in theearly gold placers of California, Idaho, andMontana were conditions favorable for theindividual miner of early years to develop a smallprofit-making operation while keeping himself fedand clothed, using no resources other than his ownsound health and optimism. From time to time,other commodities are mentioned as the hope orrefuge of the small miner, such as tungsten,uranium, and quicksilver, but over the long run,most metal production comes from large efficientoperations requiring huge capital investment.

In the rare instance where a prospector issuccessful in finding a promising mineral showing,his first thought is almost always to sell out tosomeone more interested than he in developing amine. Much of his off-season activity is in thesubmittal of his prospects to establishedcompanies. The prospector does not considerhimself to be a miner, although he often seekstemporary employment at an operating mine inorder to replenish supplies, pay bills, or to wait outthe winter season.

There is obvious romantic appeal and adventurein prospecting, and the possible financial rewardwould seemingly be an irresistible incentive. Greatpersonal satisfaction can be derived from watchingone’s preliminary idea of a prospect develop into animportant resource. However, few people seemable to become proficient at prospecting or to stayat it long enough to be reasonably confident ofsuccess.

Considering the nature of ore deposits, minerals,and the enclosing wall rocks, it is obvious that thefundamental basis for all prospecting is the scienceof geology. To be effective, the prospector must

possess considerable geologic knowledge andinsight. It does not follow, however, that theprospector must be a geologist. Many geologistsare poor prospectors. They are trained to moverelatively rapidly across the ground, recording andinterpreting a variety of information, often of littledirect significance to ore potential but necessary forcomplete reports and maps.

Most professional geologists are salariedemployees or contractors and are reimbursed forfield expenses. Few prospectors are supported, ifat all, beyond a minimum subsistence level. Thetypical prospector depends largely or entirely uponthe development of his mineral discovery forfinancial reward, recognition, and his own personalsense of achievement. A small number ofprofessional geologists work independently inmineral exploration, obtaining financial support fromsmall companies or investors’ syndicates.

Corporate geologists involved in the search forminerals most often work as a part of a team ofprofessional specialists, technicians, contractors,and consultants. The exact makeup of this groupvaries from one area to another, and depends to agreat extent upon the particular concepts andtechniques employed.

Typically, in addition to the geologist, suchdiverse talents are represented as those of thegeochemist, geophysicist, mining engineer,metallurgist, attorney, mineral economist,photointerpreter, computer expert, laboratoryscientist (such as a mineralogist), and fieldtechnician. Any of these company personnel mightrefer to himself or be called an explorationist.Although the exploration work that he performsmight sometimes be described as prospecting, hedoes not think of himself as a prospector, nor is itlikely that anyone else would refer to him in thismanner.

PROSPECTING

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Usually the corporate explorationist’s activitiesare called mineral exploration, or regional mineralexploration where there might be risk of confusionwith physical exploration-the systematic probing ofa specific prospect by trenching, drilling, orunderground work.

Prospecting is therefore usually the work of theprospector or the independent geologist, andincludes ground reconnaissance and preliminaryaerial observations. Only in special situations issystematic physical work such as sampling anddrilling done at this stage. A corporate group usuallyrefers to their preliminary mineral reconnaissanceas mineral exploration. Exploration at the projectlevel, such as drilling, trenching, and diggingunderground openings, is called simplyexploration, and considerable confusion can resultwhen someone unfamiliar with the specificdefinitions, used by an exploration group first comesin contact with them.

Prospectors can rarely afford to explore their ownprospects to any extent, and must interest a wellfinanced, established mining organization. Ingeneral, most prospecting or regional mineralexploration is done before property acquisition isundertaken. Exploration is almost never starteduntil property acquisition is complete.

The ConventionalProspector

There are few people actively interested inprospecting today who do not have some basictraining in science or engineering, if nothing morethan the typical requirements for graduation fromhigh school or an infantryman’s map reading course.Each year the opportunities expand for the averageinterested person to study subjects such as basicgeology and mineralogy. Short courses inprospecting or in specialized aspects of mineralexploration can be attended by the privateindividual, although the location and timing of suchofferings are not always convenient.

Rather than describe today’s conventionalprospector as lacking in formal training, it would bemore accurate to refer to him as a person who hasnot been completely trained as a professionalgeologist and does not undertake geologic work forothers on a professional basis. A proficient

prospector will have trained himself well enough tobe able to conduct independent investigations intogeological relationships he knows to be, or hasbeen told are, important in ore localization.

The greatest opportunity for the modernprospector is in following the development of newconcepts of ore localization and new techniquesand instrumentation, which will allow him toconfidently go back into areas intensivelyprospected before by oldtimers. If the prospectorcannot find a new ore target or a new approach, hedepends far more upon a stroke of luck thanprudence would justify.

An easily read and comprehensive book onprospecting has been published by the CanadianDepartment of Mines and Technical Surveys(“Prospecting in Canada,” by A. H. Lang, Thirdedition, 1970). This serious treatment of the subjectemphasizes Canadian conditions, but most of itapplies to prospecting anywhere. It is an excellentsource of information for both novice andprofessional.

The modern prospector has advantages over theoldtimer in the form of better equipment, 4-wheeldrive surface vehicles, and aircraft. Access intoareas of interest is far better, and water, diet, andhealth conditions are not the serious problems theywere under more primitive circumstances. Somemining experts would counter with the observationthat the early prospector had to go in and stay in,making him much more effective than some of themodern dilettantes.

To become truly competent as a prospector, aperson should be prepared to devote at least asmuch time as he might to become skilled at someother occupation such as automobile mechanic orcarpenter. He should read trade journals such asthe “Engineering and Mining Journal,” newspaperssuch as the “Northern Miner,” and Governmentpublications such as “Mineral Facts and Problems”by the Bureau of Mines and “United States MineralResources” by the Geological Survey. The lattervolume furnishes many important facts concerningmost mineral resources of interest, and containsmany specific suggestions on prospecting forvarious ore types.

To a lesser extent than in other vocations, it ispossible for the beginner to seek out a seasonedprofessional prospector and to learn from himdirectly. Such an apprenticeship would obviously

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be of great value to the novice, but there is rarely anincentive for the experienced hand to share hisknowledge and experience.

An experienced prospector who can effectivelycommunicate with people has little difficulty todayin obtaining company support or the backing of asmall investment syndicate composed of localprofessional or business people. The United Statestax laws encourage such individual investments,inasmuch as some exploration expenses can bewritten off against other income. Long-term capitalgain schedules can be applied to some profits, anddepletion allowances are an additional incentive tothe investor.

For a variety of reasons, the number of full-timeprofessional prospectors in western North Americahas steadily dwindled, and most of the importantdiscoveries of recent years, particularly in the UnitedStates, are the direct result of mineral explorationdone by corporations or by independent geologists.

Amateur ProspectorsIn recent years, as full-time professional

prospectors have almost disappeared from thescene, amateur prospectors have become far morenumerous. To many outside of the mining businessit is difficult to distinguish between the two.

The publicity, sometimes highly distorted, givento rushes such as the uranium boom of the 1950’s,the convenience of modern off-road vehicles, andthe increasing amount of leisure time available to somany, have combined to produce tens ofthousands of amateur prospectors. Some of theseindividuals make great efforts to equip and trainthemselves, and they are capable of findingprospects worthy of exploration and development.However, the majority of the amateurs are poorlymotivated and so lacking in the most rudimentaryknowledge that they create difficulties for thoseseriously engaged in prospecting and exploration.

The amateur’s common lack of consideration forthe rights of land owners, his abuse of laws andregulations, and his ill-conceived bulldozing of thesurface have become so offensive that there ismounting pressure for drastic restrictions on all

prospecting and exploration activities. A greatdeal of wisdom and fine judgment will be requiredin finding ways to regulate the recreationist-prospector while not unduly restricting seriousprospectors and geologists upon whom theNation depends for future mineral discoveries.

Regional MineralExploration

When an established mineral organizationundertakes the exploration of a large new area,some considerations are simple andstraightforward. Aside from the obvious desire tocontinue in the business of producing minerals, theorganization may consider:

1. Need to diversify.2. Need to satisfy customer demand for a metal.

Some manufacturers, after years of dependenceupon outside suppliers, may decide to enter themining field themselves.

3. State laws, local regulations, and attitudes mayencourage exploration in a given region.

4. The company may be well established in someother profitable resource industry such aspetroleum, and be prohibited by antitrust laws frompurchasing ongoing mineral-producing companies.In such cases, entry into the mining business is saidto be “via the exploration route.”

5. The desire to achieve or maintain a reputationas the major supplier of a certain commodity, sothat exploration leads of all kinds are investigatedfor this commodity, wherever they may be found.

As preliminary planning continues, acombination of such considerations as these, guidedto a large degree by the personal judgment of a fewindividual decision makers, will quickly focusattention upon certain areas, often principally by aprocess of elimination. The resulting area ofinterest might be roughly 100,000 square miles inextent, something less than the area of one of thewestern States. It may not be possible to furthernarrow down the area of interest without at least asmall amount of preliminary field reconnaissance.

In preliminary planning, a certain amount of“elephant country” philosophy is involved in

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selecting regions in which to hunt. That is, one goesto Africa to hunt elephants. For example, inplanning the exploration for large low-grade copperdeposits, the obvious potential of the Arizona-NewMexico-Sonora region cannot be matchedelsewhere. Here, many great porphyry copperdeposits are developed literally within sight of eachother, and large new deposits continue to bediscovered in the region. There is probably no otherarea on earth so intensively explored during thepast decade.

Wyoming and northwestern New Mexico have animpressive number of large, bedded uraniumdeposits that can be mined by open pit methods,and general geologic conditions are permissive ofmany more such occurrences. In north-centralNevada, a zone consisting of a dozen or solow-grade “invisible” gold deposits has recentlybeen identified in which the important new Carlindeposit (the first major open pit gold mine in NorthAmerica) was recently discovered and is now beingmined. Geologic conditions in the surroundingregion suggest that similar additional depositsremain undiscovered and, in terms of hunting forgold deposits of the Carlin type, this area is spokenof as “elephant country.”

Exploration ConceptsOnce an area of manageable size has been

selected for regional mineral exploration, the firststep is to assemble all pertinent information such aspublished geologic maps and reports, privatecompany data, commodity maps, topographic mapcoverage, and aerial photography. Some or all ofthese basic data are usually compiled on somesuitable small-scale map, such as the 1:250,000U.S. Army Map Service sheets published by theGeological Survey. If the quality of publishedgeologic mapping permits, the basic geology, orskeletonized versions of it, is compiled. Theobjective of this work is to define those areas whichcontain the right combination of geologicalconditions to localize an ore deposit of the kindsought.

To illustrate the procedure, one of the ore typesof interest in western North America today is tung-sten (scheelite, CaWO4) mineralization found in

distinctive skarn zones (fig. 3), where lime-silicatealteration formed around certain igneous intrusionsin calcium-rich rocks such as limestone. Thecompilation for exploration of this ore type wouldemphasize the following geologic characteristics ofthe ore type; and the information would be gatheredfrom literally thousands of different publishedsources:

1. The location and character of igneous intrusives.2. The distribution of calcium-rich formations.3. Previously discovered scheelite mineralization.4. Showings of skarn.5. Prospecting activity, particularly near known or

suspected igneous intrusions.6. Areas overlain by younger sedimentary and

volcanic formations should be delineated carefully,for these rocks cover the tungsten deposits.

Although this is a simplified description of thesteps taken to evaluate a region for a simple oretype, it illustrates the approach often used forwhatever kind of ore sought. The emphasis ondifferent kinds of geologic evidence varies from oneore type to another. The characteristic that may beimportant in searching for one kind of ore may havelittle or no significance in hunting for another. Amore detailed discussion of the criteria for therecognition of various ore types is given in thechapter titled “Exploration.”

A number of features of interest in regionalmineral exploration can be interpreted directly onvertical aerial photographs, available from thevarious Government mapping agencies or takenespecially for the purpose.

Most regional exploration leaves few marks uponthe ground, and the work of the prospector orgeologist cannot be detected after several stormswash away the imprint of his boot. For every pit orother obvious sign of former prospectors’ interest,there are thousands of acres where the signs ofmineralization were too feeble to have attracted hisattention. Much exploration today is done fromaircraft or surface vehicles identical in everyrespect to other surface users, and only the mostexperienced observer is able to distinguish theexplorationist’s activity from the comings and

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goings of other scientists, resource managers, andoutdoor enthusiasts.

The corporate exploration geologist will usuallyhave received extensive indoctrination from hissuperiors concerning the various rules to beobserved on public land and the need forcooperation with agency representatives. He willbe correspondingly receptive to reasonablesuggestions or instructions, particularly where thelaw or regulation clearly covers the situation inquestion.

Preliminary Evaluation ofExploration Results

Once specific areas of mineral potential havebeen defined, the results of prospecting orreconnaissance work are submitted tomanagement before proceeding with propertyacquisition and physical exploration. Every mineralexploration project requires preliminary estimationof the merit of starting the work required to exploreand develop the prospect.

The prospector or geologist makes an initialrough estimate of the general form and character ofthe expected ore body. The prospector uses thisoriginal concept of ore in attempting to interestpeople in taking over or financing his prospect. The

geologist uses his concept in presenting the projectto management.

Often the preliminary report contains carefullyprepared maps, quantitative data, photographs,and geologic cross sections. In larger companies,where many different exploration proposals may beconsidered simultaneously at regularly scheduledmeetings, simplified diagrams are prepared toconvey complex relationships and to serve as afocal point for discussion and decision making.

Each mining group or company has a differentobjective in terms of size and type of operationdesired. The small mine that might be financiallysuccessful for a small group or individual isnormally of no interest to a major corporation.Mining ventures must be capable of producingearnings of at least 5 to 10 cents per share if theyare to be of interest to the typical mining company.

Up to this point, the area being explored may havegone through a continuing process ofevaluation, however unsophisticated and incomplete.Analysis of cash flow is almost always done beforethe decision is made to proceed. These preliminaryevaluations are usually not identified as “feasibilitystudies,” although some of the same methods maybe used in deciding whether or not to continue. Amajor feasibility study and thorough evaluation isrequired to justify the multimillion dollar capitalinvestment typical of a major mining operation.

Figure 3.—Skarn tungsten mineralization.

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The selection of a small area for detailedexploration may be the result of regionalreconnaissance, a spot check of promisinggeologic situations described in publishedliterature, submittal of a proposal by a prospector orindependent geologist, or the decision to restudyan old mine or mining district.

The area selected for detailed work usuallyembraces additional ground outside the area ofactual interest. This surrounding ground may not beconcentric to the prime target area. A total of lessthan a square mile to as much as 10 square milesof land may be involved, depending upon the typeof mineralization being explored. For example, thearea required for a small high-grade mercury orgold prospect may consist of 10 to 100 acres, amassive sulfide base metal prospect a square mileor more, and major potash or phosphate potentialmight require acquisition of several square miles ofproperty.

Mineral rights are secured as soon as possibleafter the area has been determined to haveexploration potential, although details of propertyacquisition sometimes go on during the planningand initiation of physical exploration work. It isconsidered good practice to locate open groundbefore making initial contact with the land ownersand prior claimants in the area. This sometimesleads to misunderstandings, because ranchersoften do not remember the relationship betweentheir private land holdings and various surfaceleases and informal agreements. They maybecome upset over activity on what they have cometo consider their private property.

When undertaking property acquisition, it isnecessary to move quickly, stake all open ground,and undertake negotiations with private land

owners and prior claimants afterward, whilecompleting the location requirements on the stakedground. A period of relative quiet usually follows thisinitial burst of activity. Local residents may becomesomewhat frustrated at the apparent lack offollow-up just when they have begun to beinterested in developments. After sufficient groundhas been acquired, detailed plans for explorationare made, usually at a regional office somedistance removed from the exploration project site.

The individual States specify the claim locationrequirements, and no two laws are exactly alike.Most States, for example, Colorado and Nevada,have changed their laws to provide for stakingclaims without performing the physical “locationwork” which became so damaging to the surfaceenvironment after the advent of the bulldozer. SomeStates require a map showing the location of theclaim. This is done so that other interested partiescan find the claim on the ground, and to eliminatethe fraudulent practice of moving claims overdiscoveries made by others—the major abuse ofthe mining laws from the miner’s point of view.

These new State laws eliminate poorly plannedtrenching and bulldozing at the time of claimlocation, but of course do not restrict or limit thecarefully planned exploration work the claimantmay later do, nor minimize assessment workrequirements.

In many regions, indiscriminate bulldozer workin performance of claim-staking requirements isa far more widespread and serious disturbanceof the surface than actual mining. Suchsenseless scraping of the surface should bediscouraged in those States where the locatorhas the option of not doing physical location workupon the ground.

EXPLORATION

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PlanningAfter mineral rights have been acquired and

preliminary estimates of profitability made,attention turns to the choice of exploration methodsto be used and the sequence in which they are to beemployed. Personnel assignments are made,outside services contracted, and necessaryequipment obtained and allocated.

PersonnelA project manager is appointed, his title and

professional specialty depending upon the kind ofexploration work to be done. Most often he will bea geologist, and he will usually remain solelyoccupied with this project through to completion.

All important contact should be with the projectmanager, for often he alone has the knowledge andauthority to make decisions and to commit thecompany to a particular course of action.Contractors’ employees are particularly to beavoided, for they may have an erroneousconception of the objectives of the work, and arerarely authorized to talk with outsiders.

Exploration projects such as drilling programsare commonly company training grounds for recentgraduates and college students on summervacation. Such junior personnel usually have animperfect understanding of the overall objectives ofthe program. Unless it is made very clear that suchemployees can be contacted, unauthorizedattempts to obtain detailed information directly fromthem are almost certain to jeopardize relationshipswith the project manager.

AccessProvision must be made for access to the drill

sites, movement of staff and contractor personnel,water for drilling supplies, and removal of samples.In the dry season, in highly fractured ground,exploration drilling may require thousands ofgallons of water per day, and a major aspect of thework becomes the constant movement of largewater trucks. Where water is scarce, the drillcontractor may purchase it on some such basis asa flat fee per load paid to the owner of a nearby wellor pond. The drills, tank trucks, and smaller vehicles

used in transporting men and equipment are heavyduty, usually with 4-wheel drive, capable ofnegotiating steep terrain over very poor trails androads.

When larger drills are employed, flat pads asmuch as half an acre in size are leveled to site theequipment, install mud tanks, and provide for samplecollection and parking for personnel. The smaller,skid- mounted drill rigs can be moved under theirown power by utilizing the cable and draw works ina winching arrangement, to move them over bareground and up steep slopes to unprepared sites.Auxiliary equipment such as pumps and tanks canbe pulled into position by the drill.

Exploration drills and related machines arepowered by gasoline or diesel engines, and requirea modest amount of fuel storage at the drill site.Electricity requirements are small, and supplied bygenerators integral within the equipment, or bysmall portable power plants of 1/2- to 5-kilowattcapacity.

Trailer-mounted air compressors are used insome kinds of exploration drilling. Small track-mounted, air-operated drills are available. Theseare maneuverable enough to work in rough countrywithout preparing elaborate .drill roads orconstructing drill sites.

If terrain conditions are unusually severe or ifroad construction is impossible, helicopters can beused to mobilize and service the drills, although atmuch higher cost. When not carefully planned andefficiently utilized, helicopter servicing ofexploration drills becomes prohibitively expensive.

Because of the large size of the drilling machineryrequired on most modern exploration projects, it israrely feasible to use horses to mobilize and servicethe work. The small portable drills advertised inrockhound newspapers are not adequate for mostexploration work, and find application only in veryspecial situations.

OccupancyWhere feasible, exploration work is based fromestablished motels, hunting and fishing camps, orranches or farms. Families are usually housed inmobile homes located in the nearest populationcenter where utility hookups are available. In more

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remote situations, semi-permanent or permanentbuildings may be necessary, particularly afterencouraging results are obtained from preliminarydrilling. The first requirement is usually for samplehandling in a geologic warehouse that can belocked.

CommunicationsElaborate communications are usually not

required on exploration projects except in the mostremote situations. On large projects, or when workextends into the severe weather season, companyor contractor may operate radios to facilitatemovement of men, equipment, and supplies, and toprovide a measure of security in the event ofsudden illness or accidental injury.

Property AdjustmentsAs attention focuses upon the specific target

area, it is sometimes necessary to makeadjustments in property or in the conditions ofmineral ownership. For example, it may becomeobvious that a certain area may be the only suitablesite for disposal of mill tailings, and planning shouldbegin to consider this as a relatively inflexible fact.

Before actual discovery of ore is made, a minoroverlapping of prior claimants’ locations mighteasily be resolved by a simple agreement to shareroyalty on production that might come from thedisputed area. It may be possible to secureagreement from all mineral claimants that verticalsidelines will determine mineral ownership ratherthan leave open the complexities of extralateralrights. Careful surveys of particularly troublesomeclaim boundaries may be contracted to a U.S.Mineral Surveyor with everyone’s agreement toabide by his survey. Reasonable discussion isusually possible before ore is found. After ore isfound, the same suggestion might result in animmediate lawsuit or the threat of leasecancellation.

Contact With Federal AgenciesIn the earliest stages of planning physical

exploration work, consideration must be given tothe operating plan to be submitted to the ForestService if the claims are on National Forest land. Upto this point, particularly if it was possible to locatethe claims without doing bulldozer work or

constructing roads, the surface disturbance beingminimal, the job may have been done without anoperating plan.

Construction or improvement of access roads,drill sites, trenches, pits, or landing areas for aircraftmake it necessary to secure an approved operatingplan. The location and nature of the work must bespecified, and the work done in such a manner asto minimize surface damage and coordinate withother surface uses.

The intent is not to regulate the mining industry orto manage mineral resources, but to minimizedamage to the surface environment. In some casesit will be necessary for the operator to submitinformation normally regarded as secret orcompetitive within the mining industry. In suchcases, information necessary for approval of theoperating plan will be furnished on a confidential,need-to-know basis, preferably to a Forest Servicemining engineer or geologist.

Geological ExplorationMethods

Understanding of the geology of the ore depositand its general geologic setting is absolutelynecessary at every step in prospecting exploration,and development. The principal method ofportrayal of this information is through the use ofgeologic maps and cross sections, which areconstantly reworked and updated as workprogresses and new information becomesavailable. Geologic maps and sections arefundamental in exploration planning, correlationand evaluation of preliminary results, and inreporting to management.

The geologic field methods most commonly usedare:

1. Geological detail is plotted directly on fieldsheets made from maps published by the U.S.Government, or made by Kelsh plotter usinglarge-scale aerial photographs taken especially forthe purpose. Geology may be mapped directly onthe aerial photographs from which the Kelsh mapwas made, or on enlargements of them, andtransferred to the topographic base afterward.

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2. Transit and stadia are used to preparelarge-scale topographic maps and to recordgeologic detail simultaneously. The plane table andalidade method, popular with Geological Surveyand petroleum company geologists, is little used inmineral exploration.

3. Brunton compass and simple optical rangefinders are sometimes used in detailed mappingwhere extreme accuracy is not required. This methodis popular with many geologists because it ispossible to work alone.

4. Brunton compass and tape (fig. 4) sometimesused to provide base control, make the topographicmap, and to record geologic detail where alarge-scale map is required of a small area. Aclosed Brunton compass and tape traverse isusually surveyed as the base control.

5. Some geologists do preliminary geologicmapping of prospects on enlargements of verticalaerial photographs or small-scale topographic mapsavailable from various Government agencies. Theinitial saving in time and cost is more than offset bythe frustration and slow pace of mapping this way.Serious errors of distortion result from enlargementto a scale suitable for exploration work.

The geologic details shown on maps andsections are observed in outcrops, excavations,underground openings, and samples taken fromdrill holes. The data obtained between surfacebedrock observations are plotted by carefulprojection and matching of known data. Inspectionof float (fragments of rock lying in the soil that arelarge enough to be visually studied) is a methodmuch used in projecting geology.

Criteria for Ore RecognitionThe geologic features of importance in mineral

exploration vary considerably from one ore type toanother, and what might be of importance in oneore type may be of minor significance in another.However, there are a few criteria for the recognitionof ore that are almost always considered,regardless of ore type, and a brief listing anddiscussion will serve to illustrate the methods of thegeologist in exploration work. Some criteria for orerecognition are:

1. Igneous rock affiliation.2. Host rock association.3. Wall rock alteration.

Figure 4.—Compass and tape method of mapping small prospects.

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4. Age of mineralization.5. Gangue mineral association.6. Trace metal association.7. Structural controls.8. Physiographic expression.9. Weathering effects.10. Ore mineralogy.Igneous rock affiliation—Many ore deposits are

associated with or contained within certain kinds ofigneous rocks. For example, chromite ores arealways found in a special kind of iron-rich rock.Some types of tungsten mineralization are alwaysfound associated with certain granitic rocks.

Host rock association—Certain kinds of wall rockact as host to specific ore types. For example,ancient reef deposits, similar to the modern coralreefs of the South Pacific, are interlayered withinmarine formations such as limestone. Fossil reefsare an important locus for a variety of importantprecious and base metal deposits.

Wall rock alteration—The mineralizing fluids thatdeposit ores sometimes permeate outward into theenclosing host rock, causing subtle changes in aring-shaped contact zone (aureole) around the orebody (fig. 5). For example, limestone surroundingcertain silver-lead ores is recrystallized to dolomite,coarsening the texture of the rock slightly, andmaking it visibly lighter in color. The aureole of wallrock alteration is quite useful in mineral exploration,for it is much larger than the ore deposit itself, and

usually is subtle enough to have escaped notice ofthe early prospectors and miners.

Age of mineralization—Some ore deposits occuronly in rocks of a definite age. For example, muchof the world’s potash is Permian in age (280 to 225million years), and the bedded barite deposits of theWest are largely restricted to formations of Silurianand Devonian age (430 to 345 millions years).Many such simple age relationships are only nowbecoming generally recognized, and the conceptwill be helpful in the mineral evaluation of manyregions.

Gangue mineral association—Many ore typeshave distinctive gangue mineral associations(undesired minerals associated with the ore) thatcan be of use in mineral exploration. For example,two major regional ore belts, the Mother Lode goldand the Foothills base metal zones of Californiacome together and mingle northwest of YosemiteNational Park. Prospectors quickly learned that theappearance of barite in float or in the prospect panwas good evidence that the mineralization was ofthe base metal type, not gold.

Trace metal associations—Many kinds of oredeposits have distinct combinations of minuteamounts of metal found in association with theprincipal ore metal, helping to distinguish one oretype from another. For example, the copper depositcontaining nickel and cobalt is of entirely differentcharacter than a copper-molybdenum association.

Figure 5.—Wall rock alteration as a guide to ore.

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Structural controls—The analysis of structuralcontrol of ore is usually of prime importance inplanning exploration, development, andproduction. On a regional scale, ore deposits maybe found in elongated rows of individual oreoccurrences or clusters of occurrences which arereferred to as mineral belts or mineral lineaments.Along these trends, above average potential for oreexists. On a more restricted scale, the ore types ofa given district may occur along a single fault orbeneath a thrust plane, focusing attention upon anunexplored block of ground. Such relationshipsmay become apparent only after the mostpainstaking detailed geologic mapping.

Physiographic expression—Individual oredeposits, and sometimes entire mining districts, arecommonly altered, mineralized, and weathered sothat the rock matrix consists essentially ofchemically unstable or soft, easily weatheredminerals and rocks (fig. 6). Erosion cuts into suchzones, and the resulting depressions are often filledwith gravel and lava flows and are usually denselyovergrown with vegetation, all but concealingevidence of mineralization. The recognition ofmineralization fringe effects, and the lateralprojection of such indications beneath cover, is anapproach used by many explorationists.

Weathering effects—Many of the mineraldeposits currently of interest consist of relatively

small specks of valuable mineral scattered througha worthless rock matrix. The ore mineralsthemselves are often chemically unstable underthe weathering conditions at and near the surface.The ore minerals of copper, silver, and uranium, forexample, rarely survive intense weathering and aredecomposed so that some or all of the metal isflushed from the outcrop in aqueous solution (groundwater). This near-surface zone of leaching andflushing is called the leached capping, and it maycontain none of the ore minerals characteristic ofthe unweathered ore deposit below. Therecognition of leached cap rock has been a verysuccessful tool of the modern exploration geologist,because the various stable oxides, sulfates, andcarbonates of metals most often remaining inoutcrop are extremely difficult to recognize andwere easily missed by earlier explorers.

Ore mineralogy—In some instances themineralogy of the ore itself may be important. Forexample, aluminum is one of the most abundantelements in the earth’s crust, yet only bauxite (arelatively rare mixture of aluminum hydroxides) hasbeen mined as an ore of aluminum.

Most geologists have a checklist of ore criteriathey think important for each ore type of interest.They might refer to the total picture of all criteriaconsidered together, as a “conceptual model” ofthat type of ore occurrence. They may also have

Figure 6.—Physiographic expression of ore.

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definite ideas about the size, shape, and grade tobe expected of this hypothetical ore deposit.Obviously, a conceptual model can be of great helpin planning exploration, during mapping anddrilling, and in all phases of the evaluation ofresults, if the risks inherent in any generalizationare kept in mind. The use of a formal conceptualmodel is often found to improve communicationswith management and to facilitate discussionsbetween explorationists, such as those betweengeologist and geophysicist.

GeochemicalExploration Methods

The recent great progress made in rapid,inexpensive methods of trace metal analysis hasresulted in a variety of applications in geology.These are referred to as geochemistry. In mineralexploration, geochemistry is broadly applied in twodifferent situations. Numerous samples are oftencollected incidental to other exploration work, suchas geological mapping of underground workings.These samples are submitted for trace metalanalysis and the results incorporated into theoverall geologic interpretation. No confusion seemsto result in calling this work geochemistry, eventhough the same term is used to describe tracemetal analysis of air, water, soil, and rock materialsas an exploration method in its own right.

Reconnaissance GeochemistryIn applying geochemistry in regional mineral

exploration, the basic requirement is for a rapid,relatively inexpensive technique that will efficientlynarrow interest to areas small enough to explore bymore detailed methods. Simple observations canbe made from the air, either visually, by the personin charge of the work, or by interpretation of aerialphotography. Black and white and colorphotographs are used, and false color effects areobtained by using special films and filters toemphasize unusual rock, soil, and vegetativeeffects.

Geobotanical methods of prospecting involve thevisual observation of changes in the normalappearance or distribution of certain vegetation.The plant may show visible toxic effects such asdeformed or discolored leaves, or unusual size. Insome cases the very presence or absence of agiven kind of vegetation may betray unusualnutritive or toxic conditions. In one region, thediscoloration of the leaves of a common tree,observed from fixed-wing aircraft, led to thediscovery of a major new copper district. In anotherarea, the wide spacing of a shrub common to theregion, with intervening ground bare of grass, is agood indication of the host rock of nickel silicatemineralization.

Various air “sniffing” devices are coming into usein regional mineral exploration. Airborne,vehicle-mounted, and sample station detectors havebeen designed to measure such indicators asmercury vapor, sulfur dioxide, and radon gas inatmospheric and soil air, which may betray aweathering ore deposit below the surface, perhapseven beneath a considerable thickness of soil.

The geochemistry of surface and undergroundwater is a reconnaissance exploration tool. Samplesfrom springs, wells, and streams may contain traceamounts of metal in solution, indicating that thewater has come in contact with a concentration ofthe metal, perhaps an ore deposit. Where surfacewater is insufficient for adequate sample coverage,a popular method is to analyze small samples of siltfrom the stream bed itself. This method enjoysgreat popularity in more arid regions because it isstraightforward and can be done by technicians.However, results have proved very difficult tointerpret and follow up, and much less streamsediment sampling is being done today than 10years ago.

RocksPerhaps the most favored detailed geochemicalexploration method at present is the collection ofrock chip samples, analyzed to determine ifsignificant patterns may guide exploration. Many ofthe elements contained in ore deposits, and thesurrounding envelope of altered rock, are notchemically stable in outcrop and may be leached

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from the surface tone. For example, a relativelyhigh grade vein of copper may be so thoroughlyweathered and flushed from the surface that noobvious copper minerals can be visually identified,and geochemical values may be far below the metalcontent of minable ore, although still high enough tobe indicative of commercial possibilities.

Much rock chip geochemistry is done in the hopethat zonal patterns may be discerned, pointing tothe area most likely to contain the ore deposit. Avery simple pattern of progressive changes,upward and outward from the central portions of thedistrict may be envisioned. A typical zonal patternfor copper veins in the Rocky Mountains, as shownin figure 7, may be quite different than for thezonation of a massive sulfide copper deposit, asshown in figure 8. Many variations of zoning areknown for different kinds of ore, and are describedin the technical literature. Some companies havedone original research and determined their owndistribution patterns for ore types of interest, oftenat great cost. Such privately developed conceptsare closely guarded company secrets.

Other than the stone bruises left by the collector’shammer, rock chip sampling leaves no surfacedisturbance of a permanent character. Rock chip

samples are transported from the project area to acentralized company or independent laboratory forpreparation and analysis.

SoilsIn detailed exploration work, residual soils are

usually present, consisting of weatheredmaterial derived from the underlying parentbedrock (fig. 9). In many cases, analysis of suchsoils reveals a pattern of enriched metal valuesover the suboutcrop of the ore, when no visiblefloat can be found at the surface. The method isfar from infallible, and there are many variablesthat are either highly unpredictable orimperfectly understood. Typically, a few ouncesof soil are collected at each sample site, rarelymore than a few inches in depth. The samplehole is usually filled in immediately and the sitemarked by fixing a sample tag to a nearby shrub.

A sample-site or campsite chemical analysis issometimes employed in soil work, using eitherthe entire sample or only the fine material, sievedfor analysis. Soil sampling does not leave signsof visible surface disturbance that remain morethan a season or two.

Figure 7.—Metal zoning in a vein system.

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Figure 8.—Metal zoning in a massive sulfide ore body.

Figure 9.—Geochemistry of residual soil over ore.

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VegetationThe biogeochemical method is used in detailed

mineral exploration where the plant material isanalyzed to determine trace metal content. Theplant may show no external evidence ofabnormality. To be useful, the vegetation must befairly evenly distributed over the area to beexplored, and should be known to be a reliableindicator on the basis of experience on similarprojects elsewhere or extensive experimentationon the project at hand.

The biogeochemical method has been usedsuccessfully where the needles of pinyon havebeen found to contain unusual amounts of uraniumover deposits of this metal. The pinyon, as in thecase of a number of other trees and shrubs, has thecapacity to selectively absorb an element throughmembranes in the root system, and to concentratethe element in portions of the plant itself. The rootseffectively act as a much larger sampling systemthan single small handful of soil collected at thesurface at one point.

The principal objections to the biogeochemicalmethod are the difficulty in obtaining good samplesand the complicated sample processing andanalytical techniques. The same part of each plantmust be collected if the results are to be significant,and in some cases the sample must be collected atthe same season of the year to yield consistentresults.

In recent years, biogeochemists have begun touse the mull (granular forest humus) found beneathtrees. This partially decomposed material is easy tocollect and analyze, and contains a sufficient amountof trace metal to be useful.

Using sampling techniques similar to those usedin botanical studies, biogeochemical samplingleaves no permanent marks of damage.

GeophysicalExploration Methods

Some ore deposits contain minerals that possessphysical characteristics that can be measured bysuitably sensitive instruments. Exploration basedon the principles of physics is called geophysics.Exploration techniques utilize such physicalproperties as density, magnetic behavior, electrical

conductivity, and radioactivity. Six basicgeophysical exploration methods—gravity,seismic, magnetic, electromagnetic, electric, andradiometric-are commonly employed in the searchfor minerals.

GravityGravity methods depend upon the relative

density of the ore deposit and surrounding wallrock, and are not much used in metalliferousexploration. Measurements can only be made atfixed stations on the ground, and complicatedcorrections are required for station position andtopographic conditions. The typical ore deposit isnot dense enough, is too small and irregular, andoccurs in a deformed structural environment,making clearly defined gravity anomalies difficult todiscern and interpret.

The method has been very successful inexploring for large deposits of petroleum, naturalgas, sulfur, and salt. Limited application has beenreported in exploration for barite.

SeismicSeismic methods have little use in metalliferous

exploration because of the relatively small size andcomplicated geology of the typical ore deposit, andbecause of the high cost of seismic work. Themethod depends upon the velocities of acousticalenergy in earth materials, and has beenenormously successful in searching for petroleum,natural gas, and sulfur, where the large depositsmay be located by simply determining attitude ofthe enclosing strata.

MagneticCertain minerals distort the earth’s field, and

where sufficiently large concentrations of suchminerals occur, variations can be measured bymagnetometers mounted in aircraft, in groundvehicles, or positioned at stations on the ground.Magnetite iron ores have been found in many areasof the world using the airborne magnetometer.

In one case in the western United States, a verylarge iron deposit has recently been discoveredbeneath several hundred feet of barren volcanicflow rock erupted over the ore deposit. Magnetic

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copper skarn, magnetic nickel ore, andasbestos-bearing serpentine associated withcertain magnetic intrusive rocks have been found,using the magnetometer. Some geophysicistspropose the use of the magnetometer to detect goldplacer deposits, because of their commonassociation with black sands largely consisting ofthe mineral magnetite.

ElectromagneticOf the various electrical methods of prospecting,

only the electromagnetic (EM) system can be usedin aircraft. Airborne EM systems have been appliedwith great success, particularly in reconnaissanceexploration for massive sulfide ores on theCanadian Shield.

Electromagnetic methods energize the groundinductively by means of an alternating currentflowing in a transmitter coil. The resulting signal,containing ground response characteristics, isdetected inductively by a receiver coil. Both coilsmay be mounted in the aircraft, or both placed onthe ground. In one recently developed variation ofthe method, the transmitting coil is on the groundand the receiver in the aircraft.

The method is relatively slow and expensive,particularly when used on the ground in detailedsurveys. It has not been widely applied to

exploration in the western United States, where oredeposits generally have poor electromagneticresponse characteristics and may be deeply anderratically weathered, further destroying the abilityof the ore to respond.

ElectricalNatural electrochemical reactions near the

surface of the earth, where metallic sulfides may besubject to weathering, can be used in the simpleself-potential (SP) method. The measuringinstrument detects the electrical current developedduring the weathering of the sulfide, as shown infigure 10.

A shortcoming of the SP method is the frequencyand variety of spurious responses obtained. A morepopular application of the electrical method is wherecontrolled electrical energy is applied to the earthand the resulting electrical behavior of the groundis observed at closely spaced stations at regularintervals over the surface. An adaptation muchused during the past decade is induced polarization(IF) where the conductivity of mineralized groundchanges with variation of frequency of the appliedcurrent, while the conductivity of barren groundremains constant. As with the SP method, IP oftenproduces misleading results and use of the methodhas declined recently.

Figure 10.—The self-potential method.

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RadiometricUranium, thorium, and potassium occur naturally

in earth materials, and being radioactive,anomalous concentration may be detected byradiometric surveys (fig 11). Only gamma radiationis useful in exploration, because alpha and betaemissions are masked by a thin cover of soil, water,or air. Gamma ray emissions penetrate only a fewinches of soil or a few hundred feet of air, so that theradioactive ore deposit must virtually outcrop at thesurface to be detected.

Geiger counters and scintillometers are easilyportable and can be held in the hand, mounted insurface vehicles, or operated from aircraft.Airborne radiometric surveys were successfulduring the 1950’s in exploration for uranium inColorado, Utah, Arizona, and New Mexico.

Remote SensingNo ore deposit has yet been found directly by the

highly publicized “remote sensing” techniques ofexploration from spacecraft. Most of the methodsused are adaptations of techniques well known andevaluated in a variety of laboratory, ground station,surface vehicle, and aircraft installations. Atremendous amount of basic scientific data is beingcollected which cannot fail to be of major value in

mineral exploration if properly coordinated withbasic geologic concepts and evaluated bypersonnel experienced in ore search.

Several applications of activation analysistechniques show considerable promise in mineralexploration, and improved versions ofinstrumentation are becoming available for fielduse. An intense radioactive source is mountedwithin lead or paraffin shielding. When the shieldingis raised so that the surf ace area to be sampled issubjected to radiation, some elements respond begiving off a radiation that is measured by a counterwithin the apparatus. The method might becompared to an interrogation-reply mechanism.

A typical portable instrument can be used only forone element, and the equipment is cumbersome,expensive, and must be operated by trainedpersonnel under Energy Research andDevelopment Agency (formerly Atomic EnergyCommission) license. In spite of these shortcomings,limited use thus far has been spectacular in suchapplications as the search for beryllium ores. Severalmajor deposits of beryllium have been found in oldmining districts generally considered to have beenthoroughly explored.

Most ore deposits in the western United States donot respond well to any kind of geophysics or are toosmall and irregular to produce an anomaly

Figure 11.—Plan showing gamma radiation over a uranium ore body.

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sufficiently distinctive to interpret and explore. Onthe Canadian Shield, the typical ores possess goodgeophysical response characteristics. Outcropswere scoured clean of weathering effects by iceAge glaciation, so that weathering does notinterfere. The thin layer of glacial drift over much ofthe region made traditional prospecting methodsineffective, and many ore deposits have beendiscovered in recent years by geophysics.Canadian explorationists are therefore much morelikely to be enthusiastic about geophysicalexploration than their colleagues in western NorthAmerica, who are more accustomed to thecomplicated, unresponsive, weathered ores of thedeserts and mountains.

The geophysical method that might be useful inone area may prove wholly inappropriate inanother. For exam pie, airborne scintillation counterswere used very effectively in radiometricreconnaissance for bedded uranium ores of theColorado Plateau in Colorado, Utah, Arizona, andNew Mexico. The same technique, when applied toexploration for uranium in Canada, was a totalfailure. It was found that the Colorado depositswere relatively high grade, and enclosed in asequence of virtually non-radioactive sediments.The Canadian exploration was conducted in aterrain of granite and metamorphic wall rocks thatthemselves were radioactive, resulting in such ahash of background signal and false anomalies thatthe airborne surveys failed to delineate usefultarget areas within the static.

In general, the most discouraging aspect ofgeophysical exploration is the spurious resultfrequently obtained. For example, the ore depositsthat furnish the best electromagnetic responses aremassive sulfides, which are found in rockscontaining variable amounts of pyrite and graphite.The pyrite and graphite, which are worthless andcommonly show no meaningful distribution patternin relation to the ores, yield a geophysical responsethat cannot be distinguished from that of the oreitself.

Many exploration holes are drilled intoelectromagnetic anomalies, only to encounterbarren pyrite or graphite. Conversely, negativegeophysical results by no means rule out thepresence of an important ore deposit. For example,the most careful magnetic survey over an “invisible”gold deposit of the kind being found in northernNevada could not be expected to delineate ore,

because these deposits contain no mineralscapable of measurably distorting magneticpatterns.

It is obvious that the application of geophysicsinvolves more than the simple ability to make theequipment work. To be successful, thegeophysicist must be thoroughly grounded infundamental ore deposit theory, or must work closelywith an exploration geologist in planning andinterpreting the work.

Restudy of Old MiningDistricts

Only in very unusual cases is it possible to reopena mine and simply put it back into profitableoperation without doing additional exploration ordevelopment. Previous mining may have beendone in ignorance of a mineral that has morerecently become of economic interest, but ingeneral, nothing of value was knowingly left by theoldtimers, or missed by scavengers during the firstyears after the mine closed.

Today, the exploration geologist reenters oldmines and mining districts with an entirely differentpoint of view and approach. He researches oldrecords and undertakes geologic work because thecharacter of mineralization may suggest thepresence of an entirely new ore type or becausecareful analysis of the geology of an old districtmight reveal new possibilities at greater depths,along a faulted trend, to one side of the oldworkings, or in some other unexplored situationnearby.

In the study of old districts, great emphasis isplaced on geology and mineralogy, because of thewealth of opportunities for inspection and samplingprovided by the underground mine openings. Muchcan be learned from the study of structural controlof the previously mined ores. Sometimes, relativelylarge amounts of money are spent to reopen oldworkings with the immediate objective only to dogeologic mapping and sample the mine.

Perhaps the most discouraging aspect of restudyof formerly productive areas is the effort and cost ofland acquisition. Complicated mineral rights suchas numerous small patented claims, fractions, lots,former town sites, mill sites, tunnel rights, andright-of-way of various kinds make this work very

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expensive and time consuming. The problemworsens with each new generation of heirs.

Although the typical difficult property situation isoffset to some extent by the enthusiasm of workingin an area where signs of mineralization abound,the project geologist must gather together enoughhard geologic evidence to convince managementto proceed with property acquisition beforeexploration can begin. If the mineral rights to asufficiently large block of ground in the typical oldmining district can be put together on reasonableterms, even for a relatively short period of time,management usually receives such projects withfar more enthusiasm than proposals for explorationin virgin territory.

Trenches, Pits,Overburden Drilling

Preliminary exploration work may be undertakenby the conventional prospector, for example, intrenching to establish the trend, width, and mineralcharacter of an ore showing protruding from soil.Many types of ore weather readily at the surface,and these surface effects must be removed if thetrue character of the mineralization is to bedetermined. Preliminary trenching and pitting maybe done with the idea of making the prospectinteresting to the examining geologist and tofacilitate his work. Sometimes, the small miner orconventional prospector refers to this asdevelopment, but this term is more properly used inconnection with the preparation of a mine forproduction after the presence and generalcharacter of the ore deposit is proven.

A large amount of the surface disturbance onpublic land is caused when the amateur prospectorthinks he has located valuable ground, and beginsbulldozing while staking claims. He enthusiasticallyscrapes into soil-covered areas of any kind with theidea that there ought to be a big mineral deposit inthere somewhere. The extreme futility is wheresuch poorly planned trenching is attempted in anarea of 50 feet of soil cover. He may often decide tobulldoze crude trails on the ridge lines while thebulldozer is on the property, because in his mindthis will improve access and something might be

blundered onto in the process.Prospectors, and company geologists as well,

have been heard to remark that they prefer to cut upthe land visibly during the act of claim location, sothat everyone will know the ground has been staked.Mining lawyers gave this advice for years, prior tothe present concern for the environment, and somestill do.

This kind of thinking has sharply diminished inrecent years, especially where modern Statemining legislation has made it possible to locatemining claims without doing physical work on theground. These new attitudes have already greatlyreduced the amount of surface disturbance overthe past 5 to 10 years. In a typical western State,tens of thousands of mining claims have beenstaked annually. This would have amounted tohundreds of acres of surface disturbance under theold location requirements.

In serious exploration by trenching, bulldozers ofvarious sizes are used. Such equipment is easilyavailable and usually is present on the project forother work such as construction of access roads orpreparation of drill sites. Mechanical or hydraulicrippers are used in tough ground; drilling andblasting are rarely resorted to because adequatesamples can usually be collected at the point wherethe rock becomes too hard to be moved by blade orripper.

If additional depth is required in hard rock, ashallow shaft is usually sunk at lower cost and withfar less damage to the surface. Where topographypermits, the trenches are laid out at an angle to thecontour so the bulldozer can more easily dispose ofthe spoil to one side. The face, or uphill side of thetrench, is used for geologic observation andsampling because it is clean of broken material, andsurvey stakes and sample tags are not knockeddown easily by livestock and vehicles. It is normalpractice to orient the trench at a high angle, as closeto 90∞ as possible to the trend of elongated bodiessuch as veins or mineralized beds.

Carefully planned trenching can contributevaluable exploration information, but muchtrenching is a complete waste of time and effort, forexample, in the fairly common situation where thebulldozer operator himself plans the work for lack ofgood supervision.

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Backhoe trenching is becoming more popular inserious exploration work. Good trench wall facesare cleanly and quickly exposed in a variety oftopographic and soil conditions, even on relativelyflat terrain where the bulldozer would not performwell. It is possible to cut backhoe trenches straightdown a hillside; in fact, this is the preferredorientation of the equipment for efficient excavationand disposal of spoil.

Surface disturbance is less than with a bulldozer,restoration of the surface is quite simple, and it ispossible to selectively place the topsoil to one sideand pile the deeper material to the other side so thatthe trench can be refilled, reversing the excavationprocess after geologic inspection and sampling ofthe trenches. It is impossible to exactly restore thesurface to original contour, because the excavatedmaterial expands as much as 20 percent or more,resulting in overfilling of the trench by this amount.Aside from reducing the surface damage, it isconsidered good practice to backfill trenches tomaintain good relations with other surface userssuch as holders of grazing permits.

Trenches were often excavated by hand inexploration work prior to World War II. Rising laborcosts and the general availability of mechanizedequipment make work of this kind too expensive tobe cost effective today. Only in extremely remoteareas, service by aircraft or pack string, is handtrenching considered feasible. Standard hand toolssuch as long-handled shovels, railroad picks, prybars, and brooms are used.

Shallow pits or exploration shafts are excavatedwhere irregular deposits are expected to extendbeneath soil cover, or where the alluvium itself issuspected to contain valuable material such asplacer gold. Soft, unconsolidated material can bedug with small backhoes to depths of 10 to 15 feet,and circular shafts several feet in diameter can beexcavated with septic tank diggers to depths ofabout inn feet. Only the uppermost weatheredbedrock can be removed by these machines, and ifpenetration into the rock itself is required, standardmethods of shafting by drilling and blasting must beemployed.

When shafting is undertaken, it is necessary tosecurely timber the upper portions of the opening,so that men and equipment can work on the bottom

without risk of material falling. Pneumatic drills areusually used, and blasting is done with stickdynamite and standard fuse and blasting caps. Thebroken material is removed using buckets hoistedby hand windlass, small winch, or power takeoffunits on tractors or trucks.

Overburden drilling is a specialized shallowexploration method used to obtain small bedrocksamples. The samples are used for geochemicalanalysis, in geophysical interpretations of variouskinds, or for some indirect use, rather than as aprime exploration method where ore itself is theobject of the drilling.

Exploration DrillingExploration drilling is primarily aimed at

determining whether or not the ore target is present,and if so, to obtain a preliminary idea as to its sizeand grade. Secondary objectives may involvetesting general geologic conditions, such as exacttype of formation present, wall rock alteration, orgeochemical zoning. In the early stages of the work,emphasis is placed on speed and cost, and ifpreliminary work is successful, a more accurateand more expensive drilling method may be used.

There are many drilling methods, butthree-percussion, rotary, and diamond drill—are byfar the most common in exploration work. Theequipment may range in size and complexity fromsimple, hand-operated augers to small-scaleversions of the rigs used in oil field explorations.

The pattern and spacing of exploration drill holesare dependent largely upon the size, geometricorientation, and internal distribution of mineralvalues of the particular kind of ore target involved.A clear conceptual model of the particular oredeposit of interest is of great help in laying out anefficient and economic drill hole pattern.

Most deposits large enough and homogenousenough to be mined by bulk methods are drilled withvertical holes arranged in square, rectangular,triangular, or fence (row of holes) patterns, as seenin plan view. Angle-hole drilling is necessary wheresteeply inclined vein deposits are being explored,and in general is more expensive than verticaldrilling.

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Hand DrillingSmall, hand-operated drills such as the augers

and sample tubes employed in soil test work havelimited application in mineral exploration. Althoughheavy-duty versions of this equipment have beenmanufactured and equipped with lightweight,aluminum drill rod extensions and tripod hoistworks,these drills are useful only under near-idealconditions, and cannot penetrate bedrock. Themost common limitation is where hard boulders areencountered in the soft soil matrix, or whereexcessive moisture is found. The principal use ofhand drills is in testing abandoned mill tailings,which are finely ground and even grained, and arecompacted well enough that the hole will stay openwithout caving while samples are taken fromprogressively deeper depths.

Many different kinds of powered augers are usedin exploration, ranging in complexity from small,hand-held, post-hole diggers powered by gasolineto the large augers used to set power poles. Themost serious limitations are again boulders in thesoil, excessive moisture, and inability to penetratefar into the bedrock.

Percussion DrillingSeveral of the compressed air drills used in

drilling and blasting have been applied toexploration. The hand-held miner’s drill, similar insite and appearance to a jackhammer, issometimes used in collecting small samples in solidbedrock to a depth of about 10 feet. Largermachines, such as the wagon drill used in highwayand dam construction, are mounted on wheels andcan be towed to difficult drill sites along with an aircompressor mounted on a trailer.

Wagon drills, as well as a variety of smalltrack-mounted, self-propelled percussion drills, candrill holes at any angle, often to depths of over 100feet. The compressed air that powers the drill is alsoused to cool the bit and carry cuttings away from theface and out of the hole, where they are collected bysimple sack holders, buckets, cyclones, or otherdevices, depending upon the accuracy required ofthe sample. Percussion drill samples are usuallyplaced in containers and taken from the drill site for

logging and processing for analysis. Largepercussion rigs, such as those used in open pitcopper mines for blast hole drilling, are too heavyand cumbersome to be used in exploration work.Churn drills, the cable tool rig formerly widely usedfor water well drilling, are no longer much used inmineral exploration, except for small specializedadaptations used in placer evaluations.

Rotary DrillingRotary drills are relatively fast and inexpensive to

operate in a wide variety of exploration conditions.Most of the rigs are truck-mounted and completelyself-contained, including the air compressor. Athigher elevations, auxiliary compressors must beprovided, because of the reduced compressorefficiency. Standard tri-cone bits drill a hole 4 inchesin diameter or larger, and drill cuttings are blown outof the hole with compressed air. A gasoline or dieselengine drives the unit.

Some of the equipment can be quickly convertedfor core sampling, although coring is lesssatisfactory and generally slower than withequipment specifically designed for the purpose.Most rotary drills are mounted on trucks that requirerelatively good roads. Angle-hole drilling is notpossible with most of the rotary equipmentavailable, and is a major limitation of the method.

Because rotary drilling is relatively rapid, sampleswere formerly piled on the ground in rows, each pilerepresenting from 2 to 10 feet of advance, each rowfrom 20 to 100 feet of hole. In recent years, practicehas been to place the samples in containers andremove them from the exploration site, partly toleave a clean drill site, but also to frustratecompetitors’ inspection of the drilling results and topermit geologic logging in more efficient conditionsat the field office.

With equipment in good condition and a skilledoperator, progress of the typical rotary rig will varyfrom several tens to several hundreds of feet ormore per 8-hour shift, and a considerable amountof sample is generated, even using the smaller bits.Rotary drilling is particularly preferred in explora-tion where the sampling or logging is done “in-hole,” as for example where uranium is measuredby scintillation probes run in and out of the hole.

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Some geologists object to rotary drilling becausethe samples are broken into small chips andfragments where the structure of the bedrockcannot be seen. Others feel that the relatively lowcost and good progress of the method more thanoffset the disadvantage of the sample obtained,and actually see some advantage to the brokenmaterial for inspection and assaying.

Diamond DrillingDiamond drilling (fig. 12) is generally considered

the most versatile drilling method, providing asuperior core sample for observation andpreliminary testing. The equipment can drill at anyangle, including upward from undergroundstations. Gasoline and diesel engines are mostcommonly used, although air and electric motorsare available. Core recovery is not always good,particularly in mineralized rock, and the method canbe painfully slow and expensive. Diamond drillersare usually more experienced and may be morehighly paid than other drillers, for the work is moreexacting.

Water is usually the drilling medium; compressedair, crankcase oil, or kerosene are used in specialsituations. The core sample is cut by a circular bitembedded or set with industrial diamonds. Thecore passes inside the circular bit face and iscollected in a core barrel which retains the samplefor removal from the hole. The material ground upby the diamond bit is called sludge, and is carried uparound the drill rod to the surface. The core isplaced in compartmented boxes and taken to thefield office.

In some cases, the sludge is carefully collectedand saved as an important part of the drill sample.Sludge is collected in specially designed settlingtanks and placed in metal cans for plasticcontainers for transport to the field office for dryingand processing. The clear water is returned for drilluse. Where the sludge is not saved, it is allowed tosettle out in the bottom of a rude pit called a mudsump, which often overflows on hillside operationsleaving an unsightly smear of light-colored drillcuttings down the slope. If drilling mud is notcarefully controlled while the work is in progress,

Figure 12.—Diamond drilling, collection of sludge samples.

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and if the mud sumps are not covered after the workis finished, a particularly unsightly and enduringblemish on the surface can be created.

A variety of additives are placed in diamond drillholes, mostly to eliminate lost circulation, when thedrill fluid is lost in fractures or caverns and no sludgesample returns to the surface. Various organic andinorganic materials such as beet pulp, horsemanure, and bentonite have been used, along witha number of specially prepared muds developed foruse in oil field drilling. Sometimes diamond drillholes are cemented with quickset concrete underpressure, which is drilled back out as soon as ithardens, leaving the hole clean and free offractures and caves. Sometimes it is necessary tocement after almost every advance of the bit inorder to pass through troublesome ground.

Steel casing may also be set in the hole toeliminate caving and lost circulation, and to insurethat a reliable core and sludge sample is obtained.By progressively reducing the bit size, and nestingthe casing, each smaller size inside the other, it ispossible to carry casing fairly closely behind the drillbit. Diamond cores commonly range in size fromunder 1 to 3 inches in diameter. It is possible toream the smaller site holes out to accept largercasing, and various combinations of drilling mudcementing, casing, and reaming are used to carrya hole to completion with the desired core size at thebottom of the hole.

In drilling vertical holes in porphyry copperprospects, it is common to cement into the bedrocka short piece of casing called a standpipe, just largeenough to receive the largest “N” casing. Thecasing will in turn accept the NX diamond bit andcore barrel, which cuts a hole 3 inches in diameterand a core 2-1/8 inches in diameter. NX bits areused to penetrate the leached cap rock over the oredeposit. As soon as the upper, enriched portion ofthe sulfide zone is penetrated, “8” casing is set inthe hole and the bit size reduced to EX, which cutsa hole 2-3/8 inches in diameter and a core 1-5/8inches in diameter. After passing through the uppersulfide zone into unenriched ore, “A” casing is setand the bit reduced to AX, which cuts a hole 1-7/8inches in diameter and a core 1-1/8 inches indiameter.

If deep penetration is desired, far below any levelfor which mining may presently be planned, it isconsidered permissible to make one furtherreduction by setting “E” casing and proceeding tothe termination depth with EX bit, the smallest usedin most American mineral exploration. EX bits cut ahole 1-1/2 inches in diameter and a core 7/8 inch indiameter. Such a sample is usually considered toosmall to be reliable in serious evaluation of largebulk mining situations. Upon completion of the hole,the steel casing is removed to be used again, for itis very expensive.

Underground ExplorationOnly in rare instances is underground exploration

the prime method of proving a prospect. A small,well-defined exploration target such as a faultedsegment of a vein might be most efficiently exploredby extending old underground mine openings orfrom new work from the surface, but in general, acertain amount of drilling is done first to at leastroughly outline the ore target.

Underground work is usually erroneouslyreferred to as tunneling. Tunnels are seldomexcavated in mining, being a basically horizontalopening from one side of a mountain to the other, asin railroad and highway construction. The Americanmetal miner refers to horizontal work into a hillsideas an adit (fig. 13). If the adit is driven along an orestructure such as a vein, this is called drifting andthe opening is referred to as a drift. If the adit cutsacross the wall rock at an angle to the structure, itis called a crosscut and the work is referred to ascrosscutting. The mouth of the adit opening iscalled the portal. Work upward from the adit level iscalled raising, and the working is referred to as araise. If the excavation is downward, it is called awinze. Raises and winzes are usually in ore,although the same terms are used whether thework is in waste or in barren wall rock.

A shaft is a vertical or steeply inclined openingexcavated from the surface. The term “inclinedshaft” refers to openings inclined from vertical to45∞ or less. When the inclination is gentle enoughto accommodate a man on foot, rubber-tired

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equipment, or conveyor belts, it may be referred toas a decline. Shafts, inclined shafts, or declinesmay or may not be in ore.

If work is undertaken underground from the shaft,a station is cut as a landing for men and equipment,and horizontal work from the station is by drifting orcrosscutting, and is referred to as a level in themine. Work on any mine level is generally inclinedgently upward away from the shaft station, so thatany water encountered will be drained toward theshaft where it can be pumped to the surface ordiverted to an inactive portion of the mine.

The methods and terminology used inexploration work are the same as in standard minedevelopment, but the openings are often driven insmaller cross sections to economize. They canlater be enlarged if they are to be used forventilating or draining a productive area, or in themovement of personnel, equipment, or ore.Excavation is usually by drilling and blasting,although soft or highly fractured ground may slowlyyield to advance by “pick and poke” methods, usingnothing but a steel hand bar.

Drilling is done with pneumatic drills, andcompressed air furnishes the power for the drill,provides air to the men at the working face, andmoves powder smoke from the heading after theblast. Holes are usually blasted with stick dynamiteand standard caps and fuses. Electric blasting issometimes used as it is safer and is more efficientthan spitting each fuse separately. The materialbroken at each blast from the face is called a roundand the material itself referred to as muck. A muck

plate or slick sheet of flat steel is sometimes laid onthe floor before blasting to facilitate shoveling ormechanical loading of the muck into wheelbarrowsor mine cars and removal to the surface bytramming.

If some of the broken material removed from themine is known or suspected to be valuable, it isplaced on a separate dump. It is quite common tofind small dumps at exploration adit portalsseparated into two, three, or even more separateportions. Careful sampling may reveal little of valuein the separated material. Small, rubber-tiredmachines are now available to load and tram fromworking face to portal, eliminating the need for railsin modest exploration programs underground.

In former years, it was possible to find minersskilled in the art of hand drilling or single jacking, thestriking of hand steel with a short-handled heavyhammer called a single jack. Such work could bedone without air compressor, air lines, or heavydrills.

Small, portable gasoline-powered drills havelimited application in exploration work, and there isconstant danger of carbon monoxide even in theshallowest of excavations.

Today there is a prejudice against undergroundwork as a prime exploration method, and usuallyunderground openings are not thought of asexploration work. Exploration is usually equated withdrilling from the surface, and any mention ofunderground openings suggests that the work hassomehow progressed to the development stage, andthat the presence of ore is no longer in question.

Figure 13.—Underground mining terms.

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Bulk SamplingIn most exploration work there is a need for large,

representative samples of the ore deposit. A finalcross-check of the grade of the deposit must bemade, as well as testing to determine the bestchoice of metallurgical method. Bulk sampling mayalso yield other valuable data of use in planningmine and haulage facilities, the treatment method,or disposal of waste.

The mining characteristics concern such factorsas the way the rock in an open pit mine may beexpected to break during blasting and to supportitself on a bench face, and the manner in which therock will cave in an underground block cavingoperation or support itself in an underground mine.Metallurgical treatment methods can be mosteffectively researched by pilot testing techniques,and disposal of waste can be carefully researchedusing the waste from these original testingprograms.

Because of the large amount of material required,bulk samples are usually collected underground.The undesired surface chemical and physicaleffects of weathering can be avoided, and there isless problem in controlling fly-rock when largesamples are broken by blasting in confinedunderground openings.

In most cases, bulk sampling produces a largervolume of material than can be readily handled. Atemporary sample plant is constructed at the site toreduce the size of the sample, yet retain itsrepresentative character, particularly as utilized fora final check of grade and in pilot scale mill testing.It is sometimes desirable to prepare arepresentative sample for prospective purchasersof the mine product.

In a typical situation, the mine-run material, blastedand mucked from individual rounds of undergroundadvance in designated test areas, is moved to aprimary surface storage bunker with a 10- to 50-toncapacity. Each round is stored separately andassigned a lot number. As each lot is removed byfront end loader and transferred to the crusher, thebunker is carefully cleaned to prevent loss or buildupof fine particles of the economic minerals. The total

storage area accommodates 2 or more days ofmine-run material.

A portable crushing plant with a primary jawcrusher, secondary crusher, and a vibrating screensystem produces a 1M-inch mill feed product.Conveyors and transfer points are covered toreduce dust loss. The 1/Pinch product is sampledwith a sample cutter producing 400 to 500 poundsper hour of sample for testing. The material is fed toa tertiary crusher producing a l0-mesh product,from which a 5-percent “split” is taken. This splittingprocedure produces 20 to 30 pounds per hour,which is bagged and sent for assay. The remainderof the crushed bulk sample is fed into a pilot plant.

Samples obtained from most exploration drillingare not completely satisfactory in preparingrepresentative bulk samples. The small samplesare too finely ground by the drill, and in other waysrendered unreliable as a sample for investigation ofbreaking, handling, and processing characteristics.

Typically, large-scale bulk sampling isundertaken in the last stages of exploration of alow-grade ore deposit to be developed by open pitmethods. At one porphyry copper property, a shaftwas sunk on a centrally located portion of thedrilled-out deposit in mineralization believed typicalof the ore body. The shaft was sunk directly on oneof the exploration drill holes, and all the materialexcavated was collected as one huge sample. Astation was cut in the shaft, several hundred feetbelow the surf ace at about the level of the lowestopen pit mining planned. From the station, driftswere driven radially outward in a patternresembling the spokes of a wheel, each driftdirected toward an adjacent exploration drill hole. Araise was driven on each of these drill holes, usingit as a pilot, to the surface.

The material from each of the raises wasseparately stored as an individual bulk sample.Each sample was separately processed, and thegrade of copper was analyzed as a check againstthe assays obtained in the original exploration drillholes. A very small upward revision of the drill holeassays was indicated, lending confidence to theenterprise, and adding millions of pounds of copperto the ore reserve available for mining.

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Pilot TestingPreliminary metallurgical “bench tests” are

performed using a few hundred pounds of ore fromthe drill core. The tests provide a general idea of themilling procedures to be used in concentrating theore.

In a major project, underground bulk samplingprovides sufficient ore to operate a pilot plant witha capacity of 50 to 100 tons per day for severalmonths. The pilot plant is a miniature version of thefull-scale plant to be built to concentrate the orefrom the mine. The design of the pilot testing plantis based on knowledge of the type of ore in thedeposit and the details of bench testing of ore fromexploration core drilling.

Details of crushing, grinding, concentrationcharacteristics, and waste disposal can be studiedover a period of time in a pilot plant. Also consideredare the effects that a change in one part of theprocess will have on another, as well as the overallefficiency of the process. Alterations are made inthe design of the full-scale plant. Costs ofconstruction, operating costs, and waste disposalproblems can be determined for use in broadplanning and in the final feasibility study.

On a large project, the pilot plant work may bedone in a plant specially constructed at the minesite. In other cases, pilot test work will be done at acentral company laboratory location, universityfacility, or by metallurgical research companiesspecializing in this work. The small operator usuallyconducts pilot testing on a very small scale, andanticipates months of modification of his full-scaleplant to insure good results.

Feasibility StudiesAt some point in the continuing exploration, it may

become apparent that the program is successful—that an ore deposit is present. Then begins the workof bringing the ore body to its full potential bydeveloping enough ore to plan a mining operation,or to completely explore and develop the entiredeposit.

In a typical feasibility study, all of the informationgathered earlier is assembled and turned over to anengineer or engineering group for evaluation. Whilethis study is underway, exploration continues as the

project geologist tests the various possibleextensions of the ore body.

Once the decision has been made to begindevelopment, the exploration geologist orprospector, who has largely been responsible forfinding the ore body, leaves the scene. For a varietyof reasons, the exploration geologist or prospectorno longer contributes effectively to the process ofmaking the prospect into a mine. Further geologicalwork, drilling, or other operations to block out oreare done by a mine geologist under the supervisionof local mine managers, who are, of course,Production oriented.

The formal feasibility study includes an economicanalysis of the rate of return that can be expectedfrom the mine at a certain rate of production. Someof the factors considered during such an economicanalysis are:

Tons in the depositGrade of the mine productMill recoverySale price of the metal or mineralCost of mining per tonCost of milling per tonRoyaltiesCapital cost of the mineCapital Cost of the millExploration and development costMining rate, tons per dayDepreciation method usedDepletion allowanceWorking capital necessaryMiscellaneous costs of operationTax rate

In many cases this information will be put througha computer to calculate the dollar value of the yearlygross sales, operating costs, operating income,depreciation, depletion, income tax, net incomeafter taxes, the cash flow and the after-tax rate ofreturn on investment. Many companies have theirown programs and computers. Outside firms areavailable to undertake this work for a fee. Prior tothe advent of computers, this informationwas laboriously calculated by a team of engineersusing mechanical equipment requiring hundreds ofcomputations and days or weeks to complete theanalysis.

Each mining organization has a minimumacceptable rate of return on investment. The cost of

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borrowing capital for the mine or of generating theneeded capital internally within the company mustbe considered. If a company has a number ofattractive investment opportunities, the rate ofreturn from the proposed mine venture may becompared with the rate expected on a differentmining venture elsewhere, or with some otherbusiness opportunity unrelated to mining. Everyorganization has a limit to the amount of fundsavailable for new capital investments.Management has an obligation to its stockholders

or investors to select projects with the best rate ofreturn.

As a general rule of thumb, a project must havebetter than a 15-percent rate of return to beconsidered by a major company. An individualcommonly expects a 30- to 50 percent rate of returnto consider investing in a mining venture. Amongother uses of the cash flow generated by the mine,these funds must finance continuing explorationelsewhere, pay for past failures, and contribute to themine’s portion of main office and general overhead.

DEVELOPMENT

After exploration has provided a rough idea of theshape and site of an ore deposit, general geologicalcharacteristics, and average grade, and feasibilitystudies have thoroughly analyzed the dataavailable, the decision to develop the property maybe made.

At this time, the owner may decide to obtainoutside financing. Standard loan financing is notoften available to mine developers. The propertymay be sold outright for cash or for stock in anoperating company, or a royalty on production maybe retained. The owner of the new ore deposit mayattempt to interest an operating group in furnishingmanagement and undertaking operation of themine for a percentage of the return. Often someform of joint venture is worked out, when the ownerof the ore deposit will agree to share the profits afterthe mine has been put into production with anoperator who is to provide the capital andknow-how to develop the mine. Even when thecompany develops its own exploration find, there is

need for careful development planning becausecapital investment is large, and mistakes are costlyfrom this point onward.

There are almost always small bothersomedetails remaining at this point that should havebeen attended to prior to the discovery andoutlining of the ore deposit. For example, a suitablemill site or town site might not have been secured,minor property ownership problems may need to beresolved, or water rights may not be secured. Forthis reason, and the fact that entirely new personnelare sent in to undertake development and may notbe fully familiar with all aspects of the program,company personnel are just as close-mouthed asever in dealing with outsiders.

The various methods involved in minedevelopment, and the emphasis given to them,depend to a large degree upon the kind of ore bodyinvolved and the mining method to be used. Someof the more common approaches to minedevelopment will next be described to provideinsight into this poorly understood aspect of mining.

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Drilling Large DepositsOne or more stages of exploration drilling,

perhaps done over several decades, may revealthe presence of a large body of what can now becalled ore, considering present technology,economic conditions, and metal prices. The entiredeposit, or selected portions of it, may now bedrilled carefully to determine its exact grade,volume, and three- dimensional outline. Thedevelopment program should furnish the followinginformation:

1. The size and shape of the ore deposit.2. The average grade of the deposit and total

tonnage of material that can be called ore withinprescribed economic limits.

3. The distribution of different kinds of ore, andthe mineralogy of ores, if more than one kind willnecessitate separate handling or treatment.

4. Geology of the ore body, particularly as it willaffect mine design and layout.

5. The location of waste rock which must beselectively cast to one side or left unmined.

6. Operating factors such as ground water,nature of the rock as it may affect blasting or rippingcharacteristics, bench level intervals, pit slopes,and need for secondary blasting.

The pattern and spacing development of drillholes requires special care because firstpreliminary ore reserve calculations are based uponthe drill hole sample data. Some bulk minable typessuch as iron, coal, phosphate, and potash usuallyhave relatively uniform distribution. Low-gradecopper or molybdenum mineralization is much moreerratic.

Statistical techniques are important in planningdevelopment drilling programs, and in the analysisof the sample data obtained. Enough holes must bedrilled to insure continuity of geologic data betweendrill holes and to assess the relation of geology tograde changes.

Where mathematical procedures have been usedin determining the layout of development drill holes,it may be necessary to adhere to a relatively rigidgeometric pattern or interval between drill holes,and this may require preparation of drill sites inpositions that would normally not be considered, atleast in the initial phases of exploration work. Thedrill roads and drill sites are often better designedand more elaborate than for exploration, because

the equipment to be used is more complex and willbe in operation over a longer period of time, andwork continues the year around except in areas ofextreme seasonal weather conditions.

Drilling Small DepositsIf exploration of a small irregular deposit indicates

the general position of the ore deposit in thesubsurface, and if a high enough grade or largeenough tonnage is indicated, there may be a tradeoffdecision whether to undertake more drilling,perhaps using more precise methods, or toproceed directly with a limited amount ofunderground development. This usually dependsmore upon the philosophy of management than onthe facts that might be presented; some productionand exploration managers prefer to drill, andcannot conceive of underground work for anythingbut production.

Usually the decision to continue drilling is madewhere costs are reasonable and there is totalconfidence in the sampling procedures. If thedeposit lies near the surf ace and can probably bemined by open pit, there is merit in a grid of verticaldrill holes to exactly define the limits beforestripping waste or attempting initial mineproduction.

There are many cases where bold explorationdrilling programs have been conducted in areas ofsmall, erratic, high-grade ore deposits. In one suchdistrict in mountainous terrain, 10 relatively deepdrill holes were put down in an old silver district, and3 of the holes intersected mineralization suggestiveof the ore mined in the past, but at scatteredlocalities, at least 500 feet vertically, and 2,000 feethorizontally from any point where undergrounddevelopment might begin. The costs of furtherdrilling, of shafting, or driving an adit were all farmore than any profit that could reasonably beexpected from an average ore deposit in the district.The question in a case such as this becomes not somuch “what do we do with it?” as “why did we getourselves into this dilemma?”

As in all phases of prospecting, exploration, anddevelopment, the prime function of the projectgeologist is to have a clear picture of the exact kindof ore sought, and the possible size and grade ofthe ore deposit as an economic entity.

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Development Shaftsand Adits

When the decision is made to do a certain amountof underground work as the first step in minedevelopment, it is essential to have the plan formining worked out. In hilly or mountainous terrain,planning is less critical because a few short editsand a raise or two (fig. 13) to the surface willinexpensively begin the development of the oredeposit and be of major value later in ventilation endin movement of men, equipment, ore and wasterock. If the terrain is relatively flat the decision toproceed is far more critical, because shafting is veryexpensive, and only a vertical shaft, well situatedwith respect to the ore deposit, will be useful duringlater production work. If enough data are notavailable to plan such work, one might seriously askif exploration information is sufficient to proceedwith development.

It is not uncommon for mines to go through two ormore stages of development and redevelopment. Arelatively modest shaft and hoisting facility might beentirely adequate to develop and mine 100 tons ofore per day in relatively rich material near thesurface. After several years, long-term plans mayindicate the need for a much larger headframe andhoist, when development of large tonnages of lowgrade ore deeper in the mine makes possible aproduction rate of 1,000 tons per day with a newand larger mill on the property. The smalleroperation may have financed the majordevelopment work, and proven the larger orereserve far more thoroughly than any explorationwork that might have originally been justified.Usually these redevelopments are not intentionalbut are the result of higher metal prices,unexpected good results in initial development,new milling methods becoming available, or otherfactors.

Blocking Out OreUnderground

In a typical underground operation, it isdesirable to postpone some of the development

work until after the mine is put into production. Inthis manner, capital investment requirementsare offset as some financial return begins tocome in. In the United States it is commonpractice to develop and produce from the upperlevels of a mine, and to later deepen the shaftand develop the lower levels in a carefully plannedschedule timed in coordination with depreciationof the surface plant. Usually some rule of thumbis adopted to insure that a ton of ore is developedfor each ton of ore mined.

At one property, a foot of development (drifts,raises, winzes) might be done for each 10 tons ofore taken from the mine. At another property afoot of diamond drilling per ton of ore may becrude insurance that the development of theproperty is a viable operation.

The yearly statement of “ore reserves,” if madeavailable in any form to outsiders, therefore doesnot accurately reflect the possible ultimateproduction of the mine. There are many reasonsfor such conservat ive pract ices; abruptfluctuations of metal prices can convert ore towaste overnight, local tax laws may be appliedon an “inventory” basis to a wasting asset, labornegotiations can become difficult if there is afalse impression as to longevity of the operation,and there would be legal questions introduced ifspeculative material were called ore bymanagement.

When a miner speaks of production plusreserves, he is making little allowance for orethat lies far ahead of present development work.Some companies have only a certain minimumtonnage of reserves on hand, and do not feel thecash required to increase the reserve figure is agood investment. Three categories of ore—proven, probable, and possible—are generallyaccepted in statements of ore reserves (fig. 14).

Proven (Measured) OreProven ore is that for which tonnage is computed

from dimensions revealed in outcrops, trenches,workings, or drill holes, and for which grade iscomputed from adequate sampling. The sites forinspection, sampling, and measurement are soclosely spaced, on the basis of defined geologicalcharacter, that the size, shape, and mineral contentare well established.

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Probable (Indicated) OreOre for which tonnage and grade are computed

partly from specific measurement, samples, orproduction data, and partly from projection for areasonable distance on geological evidence isconsidered probable ore. The openings orexposures available for inspection, measurement,and sampling are too widely or inappropriatelyspaced to outline the ore completely or to establishits grade throughout.

Possible (Inferred) OreQuantitative estimates of possible ore are based

largely on knowledge of the geological character ofthe deposit and few, if any, samples ormeasurements. Estimates are based on assumedcontinuity or repetition for which there is geologicalevidence; this evidence may include comparisonwith deposits of similar types. Bodies that are

completely concealed, but for which there is somegeological evidence, may be included.

The terms proven, probable, and possible areused by mine operators to distinguish the orecategories in a single mine or perhaps, at most, amining district. Locally, much more rigorousdefinitions of proven, probable, and possible areused. The terms measured, indicated, and inferredare applied in a much broader sense, such as inexpressing the reserves of the bedded phosphateore in a western State, and are employed mostly byFederal and State agencies, mineral economists,academicians, and commodity analysts.

AccessBecause of the heavy flow of traffic and large

equipment involved, the requirement for good

Figure 14.—Partially developed vein, three ore categories.

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access roads is generally greatest during minedevelopment. Many western States and countiesmove construction and maintenance of improvedroads into a position of first priority in their budgets,especially where a good road can be easilyconstructed from one of the county’s towns directlyto the mine. The county then not only receives thetax benefits provided directly by the miningoperation, but also retains the much largersecondary benefits of commerce and employmentand tax revenues from them. The tremendouseconomic impact of a new mine operation is oftennot fully appreciated by economists and land useplanners more accustomed to dealing withagriculture or normal urbanization, and the financialimpact may come as somewhat of a bombshell tolocal planners.

The access roads to a property being developedby underground methods are often in canyonbottoms and stop at the site of the main shaft of aditportal on the main development level. Additionalroads over the surface of the ore deposit are notusually necessary, except to service ventilationequipment in a second exit or for other servicefunctions specific to the site.

Where large deposits are being developed bydrilling and open pit methods are planned, buildingaccess roads for drills is a major undertaking, andsurface disturbance is at a maximum, especially inthe area immediately over the ore. These roads canbe extremely unsightly because they are so closelyspaced and often traverse steep hillsides where nonormal road would be planned. They will beremoved during stripping and mining or will becovered by waste dumps placed around the pit asdevelopment and production continue. In general,the access roads on private property will be paid forentirely by the mining company, although they maybe later opened to provide access for the public torecreational areas, vistas of the mine operation, orother areas of general interest.

PowerThe requirement for electricity in mining

operations is usually large from the developmentstage onward where essentially all power iselectrical except for mobile units, such as trucks.

Large developments usually involve contracts withpower companies and public utilities for newtransmission lines and substations necessary tobring outside power into the property. At smallerproperties, or those in very remote locations farfrom low-cost sources of electricity, dieselgenerator sets are installed within the mine-millplant complex. The principal considerations are asite suitable for unloading and storage of bulk fuel,distance of transmission of power, and position ofthe plant away from residential areas because ofthe noise.

Energy for the powerplant is usually derived fromwater or hydrocarbon fuels in typical miningsituations. The diesel-engine generators especiallyadaptable to smaller locations have outputs up to15,000 to 20,000 kilowatts and can be preengineeredby manufacturers to company specifications. Steamgenerating plants generally have a minimumeconomic output of 5,000 kilowatts. Where publicutility or Government power is available, the mineowner usually finds it cheaper and more reliablethan generators, and he will share in the cost ofconstructing the connecting line from the closestexisting utility line. Up to a connected load of about1,000 horsepower, it is cheaper to let the utilityprovide a primary substation; above thishorsepower a more favorable rate may be obtainedby constructing a private primary substation totransform incoming power to usage voltages.

CommunicationsAt most locations, entry into the development

stage calls for planning full telephonecommunications for the mine and mine community.In the western United States, mine operators arenot as aviation conscious as in similar areas ofAlaska or Canada, but some thought is usuallygiven to a small landing strip or helicopter landingarea for direct air evacuation of seriously ill orinjured personnel.

As development continues, limited medicalfacilities are constructed, but the nature of mine andmill industrial accidents is such that immediate airor other rapid evacuation of victims is contemplatedto the specialized medical facilities available only inthe larger communities. Many companies maintain

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company-owned ambulances or enter intocontractual or cooperative agreements with othersfor ambulance service.

Site PreparationThe location of the ore deposit determines the

mining method, and once the choice is made, thesiting of surface facilities is a relatively inflexibleanalysis or checkoff to determine which locationbest meets requirements.

MineIf a vertical shaft is to be the main development,

it may be desirable to sink it in barren wall rock atone end or to one side of the ore deposit to keephaulage and hoisting facilities clear of actualunderground mining, yet minimize tramming of oreunderground to the mine exit. Inclined shafts anddeclines allow a measure of flexibility, for they canbe directed from a suitable surface point to the idealposition underground. Horizontal development byadit is the most difficult to plan in some respects,and is usually considered only where topographicrelief is considerable. Development by adit ispreferable because water can be drained withoutpumping, and level ore haulage systems require farless energy and capital investment than hoists overshafts or conveyor systems in declines. Also, theore and waste can be taken down and out of themine at minimal operating cost.

The mine plant must be suitably situated foraccess by road. The ground beneath must besuitable for support of building foundations, and thearea should be free from risk of landslides,avalanches, or unusual runoff during the variousflood seasons.

The basic mine plant for underground miningoperations consists of headframe, hoist, timberframing and storage area, miner’s change house,compressor house, machine shops, warehouse,office, ore storage, and ore loading and shippingfacilities. In unusually severe topography, theore may be hauled by truck, conveyor, or aerialtramway to the treatment plant, and coarsecrushing may be done at the mine. Normally theore treatment plant is placed as close to the mineas possible to reduce handling, and in somecases to facilitate return of the mill tailingsunderground as fill to support stoped areas (seefig. 13, 15).

In many underground mining situations, thesurface plant can be located directly over themine without fear of damage due to subsidence.Where large amounts of development must bedone in barren wall rock, and the resulting wastecannot be disposed of in cut-and-fill stopes, it isnecessary to provide for waste dumps near thecollar of the shaft or portal of the adit.

In open pit operations, large areas are requiredfor roads, mining, stripping, disposal of wasterock, and low-grade stockpiles or heap leachingoperations.

Figure 15.—Open stope mining method.

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Extensive parking areas are required if theemployees travel to work by automobile. Whenspace is restricted, remote parking areas areserviced by shuttle buses to take the men to theworking area. If the mine is in a very remote region,temporary housing and meal facilities may beprovided for visitors, maintenance personnel, andtop management.

An effort is usually made to locate and constructthe mine plant in harmony with the localenvironment, but safety and fire insuranceconsiderations may dictate a certain amount ofcareful clearing of forest around the surf aceinstallations so that they may be protected fromforest fires. This also minimizes the risk of ignitingthe surrounding forest if a fire starts within the plant.

In extremely difficult surface situations, mineplants, and in a few cases the ore treatmentfacilities, have been installed underground as amore economical measure than attempting tocombat steep terrain, bitter low wintertemperatures, or risk of avalanches. Today muchconsideration is given to locating the surface mineplant in some side canyon away from public view,even if this may involve a longer haul for ore andwaste and extended access roads. With planningand a slight additional investment, it might bepossible to have the entire mine operation out ofsight of the average tourist.

MillIn former years, mills were generally constructed

on hillsides to utilize gravity to feed ore and waterthrough the plant. Today, construction costs andworkers’ demands favor construction of millfacilities on about the same level as the mine. Themill is situated at some convenient site between themine and the mill tailings disposal area. The mainoffices and powerplant are usually located at themill, where mine and mill are separated.

Ore crushing, blending, and storage units mustbe accommodated, as well as the mill structureitself and warehouses, loading, unloading, andweighing facilities. Loading and turnaroundfacilities for trucks and railroads may be a majorspace requirement, where large amounts of ore orconcentrate are shipped or large quantities of minesupplies and mill reagents are received.

Town SiteWhenever possible, mine planners try to avoid

getting into the business of providing housing,public buildings, streets, schools, and playgrounds.They will make every effort to utilize and expandexisting facilities in nearby towns. The idea held informer years that an additional profit could be madefrom the company store and other tightly controlledfacilities has given way to an open attitude wherethe company will help support local schools, trailerparks, and medical and other facilities, with privateindividuals or independent groups responsible fortheir operation.

Where a town is built for company personnel,suitable space must be provided for a small city inno way different from a mature community, exceptthat all applicable building codes will necessarily beadhered to and the facilities commonly serve alarger proportion of younger families. The town sitemay be close to mine and mill, so close that theaverage employee can walk to work. The housingprovided for families usually is an added cost of theoperation, but living facilities for unmarried workersmay come much closer to breaking evenfinancially. North American mining communitiesaverage about five persons per family, and the ratioof married to single employees varies dependingupon the isolation of the project.

In extremely remote situations, unusualschedules are established so that employees workrelatively long shifts for short periods, with highwages and frequent short vacations, and freetransportation home to their families and back. Atthe mine, bachelor facilities are provided for allworkers. The operation is expected to yield a higherthan normal return on investment to offset theseincreased labor costs.

Postponement ofProduction

Sometimes, after the excitement of the originalland acquisition and exploration drilling, work on amine project is halted. This is perplexing to localpeople, some of whom may have begun to makechanges in their personal and business lives in

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anticipation of the new mining operation. There aremany reasons why a mining company may delayputting property into production. There are alwaysrumors going around when this happens, andbusiness people and community leaderssometimes call for a clear statement of intent, sothat everyone will know what to expect.

Sometimes it is possible to make suchstatements, and periodic updates may be issued inthe interests of community relations. Just as often,company management has been so taken abackby an unforeseen or uncontrollable event, or seriesof events, that they do not know what the best planfor the future might be. Rather than issue a falsestatement, or speak in generalizations tantamountto falsehood, the company may choose, or beadvised, to remain silent. The local projectmanager sometimes has no authority to discuss thefuture of the project, and a meaningful statementcan only be obtained from higher management.

Although there are cases when a company maydecide to delay further development, it is not usuallyadvantageous to do so. A considerable capitalinvestment must then lie idle, providing no income.Such items as the wages of standby personnel andwatchmen, costs of insurance, taxes, minimumpayments on property, and assessment work onclaims add up to a major expense and accomplishnothing productive. The morale of projectpersonnel is also a consideration; professional staffprefer to be associated with a live project, where asense of accomplishment can be gained from theday-to-day activities of a successful operation. Tothe individual professional person, assignment to adormant project often translates into a dormantprofessional career.

Some typical reasons why a company maydecide to delay production are: (1) A portion of themining property, water rights, surface rights, orother legal rights still has not been acquired; (2)better market conditions may be anticipated; (3)equipment or personnel may be coming from otheroperations; (4) an assortment of unrelated prob-lems might best be solved by simply waiting themout.

Many and varied are the reasons why a companycannot put the property into operation immediately,

and some of the more critical ones are completelybeyond the control of the company:

1. Drop in price of mine product, or no rise inprice if this had been anticipated.

2. Increase in labor costs.3. Unfavorable legislation or regulations.4. Change in tax laws or assessment

procedures.5. Threat of litigation.6. Action of private conservation groups.7. Lack of smelter or refinery capacity.8. Lack of capital.9. Delay in obtaining delivery of major

equipment.10. Lack of transportation facilities.

Although one or two of these considerations, orsimilar ones, may be the paramount reason forpostponing development of the mine, there areusually many other factors involved, and the “go” or“no go” decision is carefully weighed against a listof favorable and unfavorable factors, some of whichmay be changing while the deliberation is beingmade.

From the standpoint of surface damage to theenvironment, it is particularly unfortunate when theproperty must be put into a holding situation. Often,considerable damage has already been doneduring the exploration and development stages,and it will remain until the decision to mine iseventually made. For example, an ore deposit nearthe surface that is to be mined by open pit methodswill have been drilled in a close-spaced pattern ofvertical holes and the close network of accessroads over the property will usually have made amess of the surface, particularly from the visualstandpoint. There are many people who findnothing particularly ugly about a well-engineeredand smoothly running open pit mining operation;however, no one would view the drill roads asanything but an eyesore.

Although some properties have lain idle for years oreven decades, most economically marginal miningproperties will someday become minable. Increasedefficiency of mine and mill equipment and increasesin metal prices gradually lower the economic “cut-off”grade for ore over the years, and marginal propertieseventually are developed.

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Prior to development of an ore deposit, the exactchoice of mining method will have been made. Thetype of haulageway for one mining method might betotally unsuitable for another method, and it isnecessary to plan for production from the verybeginning. Underground methods of mining arecalled stoping by the American metal miner, andare particularly varied.

Underground MiningMethods

The various stoping methods have evolved overthe years to cope with particular conditions or totake advantage of certain kinds of labor,equipment, or new techniques as they becomeavailable. In selecting the most appropriate stopingmethods, the size and shape of the ore body is themost important consideration. Overburdenconditions, strength of ore and enclosing wall rock,water, value of ore, and other factors must also betaken into account. Although there are minorvariations or modifications of most of the stopingmethods, it is usually possible to clearly identify thebasic method in use at a given mining operation.

Open StopingSmall ore bodies are often mined completely out,

leaving no pillar of ore in place to support the wallsof the stope. In some kinds of rock, it is possible tomine out huge stopes which stand open (fig. 15) foryears.

Where some of the ore body is left in place asrandom pillars to support walls, the material islow-grade wherever possible because it may never

be removed from the mine. Sometimes, after openstoping a mine, the pillars are “robbed” just beforeabandoning that portion of the mine, and thecollapse of the stope walls is of no concern to theoperation. Sometimes narrow veins can be openstoped, placing an occasional wood stull, or woodbeam, from one wall of the stope to the other. Thisis called stull stoping. The stulls serve to support thevein walls, and as places to anchor wood platformsupon which the miners and equipment stand whiledrilling ore overhead.

Room and pillar mining (fig. 16) is commonlydone in flat or gently dipping bedded ores. Pillarsare left in place in a regular pattern while the roomsare mined out. In many room and pillar mines, thepillars are taken out, starting at the farthest pointfrom the mine haulage exit, retreating, and lettingthe roof come down upon the floor. Room and pillarmethods are well adapted to mechanization, andare used in deposits such as coal, potash,phosphate, salt, oil, shale, and bedded uraniumores.

Shrinkage StopingShrinkage stoping (fig. 17) is done by stoping the

ore deposit from beneath, allowing broken ore tosupport the stope walls, but leaving a space abovethe broken ore just sufficient for the miners to standon and drill overhead. Broken ore is drawn asnecessary to maintain this headroom, and becausethe volume of rock expands upon breaking, abouta third of the broken ore is drawn from beneath asstoping progresses from the bottom of the ore blockto the top.

After the stope is completed, all broken ore isremoved and the walls are allowed to cave in. The

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wall rock must be strong enough to support itselfduring shrinkage stoping, without breaking awayand becoming mixed with the broken ore. Steeplydipping veins with well-defined, hard walls are mostsuitable for shrinkage stoping.

Cut and Fill StopingThe development work for cut and fill stoping is

similar to that for shrinkage stoping, except that aseach cut of ore is removed, a layer of waste is

placed in the stope to support the stope walls andto serve as a platform for miners and theirequipment. All ore is taken from the stopes as it ismined, through tightly timbered raises up throughthe fill, called ore chutes. Broken waste rock iscommonly used for fill and usually comes fromdevelopment headings elsewhere in the mine. Thispractice makes it possible to dispose of waste rockunderground without the expense of hoisting it tothe surface for dumping.

Figure 16.—Room and pillar mining method.

Figure 17.—Shrinkage stoping.

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A variation of the cut and fill stoping methodsinvolves returning carefully sized mill tailings in aslurry to the stopes underground, where the slurryis hosed into place as stope fill under the pressuredeveloped by the head. Water quickly drains fromthe tailings fill, which becomes compact enough tosupport the weight of men and equipment as theycontinue to stope overhead. This method isreferred to as hydraulic filling (fig. 18) or sand fillmining and is a convenient way of combining thesolutions to the stope fill and mill tailings disposalproblem.

Rill stoping is cut and fill stoping where the slicesare inclined to the horizontal, so that ore movesdown out of the stope, and waste slides down intothe stope from above, without the need for handshoveling or mechanical scraping. Cut-and-fillstoping methods are used where one or both wallsmay be weak, so that they would collapse into thestope to mix with broken ore if not carefullysupported.

Square-Set StopingThe square-set method (fig. 19) is used where

the ore is weak, and the walls are not strong enoughto support themselves. The value of the ore must berelatively high, for square-setting is slow,expensive, and requires highly skilled miners andsupervisors. In square-set stoping, one small blockof ore is removed and replaced by a “set” or cubicframe of timber which is immediately set into place.The timber sets interlock and are filled with brokenwaste rock or sand fill, for they are not strongenough to support the stope walls. The waste rockor sand fill is usually added after one tier of sets, orstope cut, is made.

Block CavingThe block caving method (fig. 20) is used in

mining large ore bodies that have a barren orlow-grade capping too thick to strip away from thesurface. In development, evenly spaced crosscuts

Figure 18.—Hydraulic stope fill.

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Figure 19.—Square-set stoping.

Figure 20.—Block caving underground.

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are made below the bottom of the ore block to becaved, from which raises are driven up to the ore.The entire ore block is undercut so that it will begincaving into the raises. The weight of the cappingand ore provides the force to crush and move theore downward, where it is drawn from the raisesbeneath, trammed to the shaft or decline, andhoisted to the surface.

As broken ore is removed, the capping willgradually descend until broken fragments of itcoming from the raises indicate that all of the orehas been withdrawn. The surface over theworked-out mine is a gigantic collapse feature, notas deep as the height of ore withdrawn, because ofthe “swell factor” of the broken capping, butconsiderably larger in diameter than the areaactually caved underground.

Surface MiningMethods

Because of the rapid development of many typesof large and efficient earthmoving machinery andauxiliary equipment, surface mining methods havemade it possible to mine many ore deposits thatwould be uneconomic to develop underground.Although there is great variation in detail, only a fewbasic methods are employed, and the terminologyis much more simple than in underground mining.

Placer MiningPlacer deposits are concentrations of heavy

minerals, usually within loose alluvium that caneasily be excavated and washed. Placer mineralssuch as gold, tin, and tungsten minerals, are ofrelatively high value, but the value of the placergravel itself may be very low, often less than a dollarper cubic yard. For deposits of such low grade to beworked they must be near water, on or near thesurface of the ground, and should be only looselyconsolidated so that drilling and blasting are notnecessary. The bulk of placer mining falls into threegroups—panning and sluicing hydraulicking, anddredging.

Panning and sluicing.—The traditional goldminer’s pan is an efficient device for washing andseparating placer minerals. However, the methodis slow, and even in the hands of a skilled operator

only small volumes of material can be processed.Most surface deposits rich enough to be mined andconcentrated by panning were worked over longago, in many cases by Chinese workers left idleafter the construction of the transcontinentalrailroad. With today’s high wages and employmentopportunities, the deposits remaining are far toolow grade to be worked on a sustained economicbasis. The gold pan is now used mainly as a tool inprospecting and exploration of low-grade placerdeposits being considered for bulk mining methodssuch as dredging.

In recent years, gold panning has become apopular outdoor recreation. There is excitementand appeal in panning an occasional nugget or afew small specks of gold. The remote chance ofdiscovering a rich pocket somehow missed by theoldtimers provides a strong incentive. In general,far more money is made selling manuals, maps,equipment, and gas and oil to these hobbyists thanis made from the gold itself. There are shops alongthe foothills of the Sierra in California where smallquantities of placer gold are sold at great markupover metal market quotations, so that the unluckyweekend gold panner need not return homeempty-handed.

In sluicing, the placer gravel is shoveled into thehead of an elongated sluice box which is inclinedand has various configurations of bars and trapsacross the bottom called riffles. Water is directedthrough the sluice box, and the heavy placerminerals are trapped in the riffles; the fine materialis washed over them and out as a relatively barrentailing. Few deposits are left unmined in the westernUnited States, where sluicing might be economicalat present gold prices.

In both panning and sluicing operations, it issometimes possible to collect very fine particles ofgold by amalgamation, when mercury is eitherplaced in the bottom of the riffles or smeared oncopper plating. The fine gold amalgamates with themercury and is collected by retorting in smalldevices which drive off the mercury as vapor,retaining the gold.

Hydraulic mining.—In hydraulic mining, or“hydraulicking,” a stream of water under greatpressure is directed against the base of the placergravel bank using pipes and large nozzles calledgiants. The water caves the bank, disintegrates the

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gravel, and washes the broken material to andthrough sluice boxes situated in convenientpositions downslope. Hydraulic mining totallydisturbs large surface areas, puts much loosedebris into the drain age system, and involves largesurface water runoff that may cause substantialdamage downstream. Many of the western Statespassed laws years ago to closely control“hydraulicking,” and few substantial deposits ofplacer gravel remain that could be minedeconomically within the restraints of this legislation.

Dredging.—Large alluvial deposits are mined byfloating washing plants capable of excavating thegravel, processing it in the washing plant, andstacking the tailings away from the dredge pond.Two kinds of equipment—bucket line anddragline—have been used. The bucket line dredgesare larger and more efficient, consisting of acontinuous line of buckets that scoop the materialfrom the gravel bank at the edge of the dredgepond, raising it to the top of the washing plantmounted in the hull. Dragline dredges are smallerand less efficient, and employ a single bucket thatdigs the gravel and is swung over the feeder hopperof a floating washing plant similar to the layout in abucket line dredge, although usually smaller.

Dredging temporarily involves total disturbanceof the ground surface, although with carefulplanning and engineering of the operation it is

possible to plan for restoration of the surface, andperhaps even to improve some aspects of the floodplain or nearby river channel. It is not possible torestore the land to the precise original contour, forthe swell factor of the gravel increases volume 20percent or more. In many areas in the West,particularly near major construction projects orcities, clean gravel placer tailings are valuable formanufacture of aggregate, or crusher run, in fills ofvarious kinds, and can be considered a resource intheir own right. In a few areas, people travelingthrough areas of old placer tailings, expecting thearea to be some sort of wasteland, are pleased tofind a great variety of fishing and water sportrecreation available, and thriving wildlife in thehabitat that has been created.

Because large placer deposits can be thoroughlyexplored before floating the dredge, suchoperations lend themselves to thorough planning,and it is possible to do a considerable amount ofreclamation at only slight increase in overalloperating costs.

Glory HolingAlmost every opening at the surf ace is referred

to by local writers and mining buffs as “glory holing”(fig. 21). Actually this kind of operation isuncommon, as it involves a mine opening at thesurface, from which ore is removed by gravity

Figure 21.—The glory hole mining method.

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through raises connected to adit haulagewaysbeneath, and by tramming the ore to the surface onthe haulage level.

The glory hole method is best suited to mining ona hillside, and irregular deposits can be cleanlymined without dilution by waste wall rock. Narrowveins have been mined by glory hole; in thesecases the “hole” becomes narrow and long. Thebenches are mined away as work descends to thebottom of the deposit or to the haulageway, so thatspectacular steep sidewalls may result if the wallsdo not slough in. Mining can be quite selective, andlittle waste rock is thrown on the surface dumps.The principal environmental objection to the methodis difficulty in reclamation of the surface of the minearea.

Open Pit MiningAlthough the basic concept of an open pit (fig. 22)

is quite simple, the planning required to develop alarge deposit for surface mining is a very complexand costly undertaking. In one mine, it may bedesirable to plan for blending variations in the oreso as to maintain, as nearly as possible, a uniformfeed to the mill. At another operation it may bedesirable to completely separate two kinds of ore,as for example, a low-grade deposit where one kind

of “oxide” ore must be treated by acid leach, but asecond kind of “sulfide” ore must be treated bydifferent methods.

The grade and tonnage of material available willdetermine how much waste rock can be stripped,and there is often an ultimate limit to the pit that isdetermined more by the economics of removingoverburden than a sudden change in the oredeposit from mineral to nonmineral bearingmaterial. The ultimate pit limit and the slope of thepit walls are therefore determined as much byeconomics and engineering as by geologicalstructure. Material that is relatively high grade maybe left unmined in some awkward spot extendingback too deeply beneath waste.

The typical large open pit mining operation thathas been in production for 10 years and more isoperating under conditions that could not possiblyhave been foreseen by the original planners of themine. Metal prices, machinery, and milling methodsare constantly changing so that the largeroperations must be periodically reevaluated, andseveral have been completely redeveloped fromtime to time as entirely different kinds of mining andmilling operations.

Figure 22.—Open pit mining.

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Sometimes the preliminary stripping of the wasteoverburden is contracted to firms specializing inearthmoving. Mining is usually done bytrack-mounted electric shovels in the largeoperations, and by rubber-tired diesel front-endloaders in the smaller operations. Scrapers aresometimes used in special situations. Largebucket-wheel excavators of the kind used inEuropean coal mines have not been applied tometal mining, because this equipment is bestadapted to softer bedded, relatively flat-lying strata.

Haulage is usually by truck, although railroads,inclined rails, and conveyor belts have been used.The conveyance unloads directly into a primarycrusher and crushed material is stored in coarseore bins prior to shipment to the mill.

Bench level intervals are to a large measuredetermined by the type of shovel or loader used,and these are selected on the basis of the characterof the ore and the manner in which it breaks uponblasting and supports itself on the working face.Blastholes are usually drilled vertically byself-propelled, track-mounted pneumatic or rotarydrills. Bulk explosives are loaded in the holes andlarge volumes of ore are broken in a single blast.Sometimes the drill holes are routinely sampledand assayed to help plan the position of the shovelsin advance of mining. Blasthole assay control isespecially desirable when exploration data areincomplete or lacking as in the case in the older pitswhich have long been mined past the limits of “ore”used in original planning.

Leaching MethodsSolution mining techniques are used for

extracting soluble ores such as potash and salt insituations where conventional mining methodswould not be economic. Total solution of all themineral is not always accomplished. Sulfur is minedby the Frasch process, using steam to melt thesulfur and bring it to the surface through bore holes.The future of solution mining appears promising, forthere is constant improvement in equipment,solvent, and in technology of breaking rock in placeand controlling the movements of fluids through it.In mining salt, potash, and sulfur, the overburdenand surface over it subside. Subsidence itdesirable, because it increases the solution of

mineral, and destroys voids, reducing the amountof solution required and the time needed for it to act.

In applying methods of solution mining totraditional ores such as the base and preciousmetals, subsidence will not be as important assurface disturbance, for the metal taken intosolutions is only a minute portion of the total rockmatrix. It has been suggested that some zones oflow- grade mineralization might be leached in place,and there is particular interest in copper and goldores, which have long been leached using “vat”processes and uranium, which is easily taken intosolution in a number of solvents.

Biologic activity is known to hasten theconversion of metal in many ores to a more solubleform. Several naturally occurring bacteria havebeen found to oxidize such insoluble minerals ascopper sulfides, increasing solubility athousand-fold over the sterile condition.

A great deal of research is being done todetermine the conditions most favorable for goodsolution of metal, and the method can be expectedto contribute significantly in future miningoperations, if not become an important miningmethod in its own right. Operators are particularlywatching developments of new organic solventsthat are environmentally acceptable, are specificfor the element desired, and do not react with orbecome consumed by wall rock.

The methods most commonly used fordistribution of leach solution are flooding pondsover the leach dump, spray, trickle, and solutioninjection. The pregnant solutions are collectedbeneath the leach zone and are pumped toprecipitation plants nearby or to the precipitationsection of the main ore treatment plant where this isfeasible.

In-Place Leaching.—Because the naturalporosity of most rocks is too low for rapid, pervasivepenetration of leach solutions, it is necessary tofracture the rocks artificially. Conventionalexplosives have been used, and one low-gradecopper deposit in Arizona is repeatedly suggestedas a likely place to research underground use of anuclear device, where breakage, heat, andpressure would combine to make the copper sulfideminerals much more soluble than in ambientconditions.

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On a more limited scale, in-place leaching hasbeen applied to fill in old mine stopes, caved areasover block caving operations underground, and inperipheral portions of conventional open pits wherethe grade is too low to permit mining the material.

This method is not well enough understood, norhas enough experience been gained to apply it to avirgin, high-grade ore deposit with assurance ofcontrol and predictable recovery of values beingleached. The method holds great promise,because capital costs are low and there are fewerenvironmental problems compared to themovement of vast tonnages of rock in conventionalmining.

Mining Dumps.—Low-grade copper minesusually employ some form of leaching for recoveryof small amounts of copper contained inoverburden and waste. Open pit gold mineoperators have begun to follow this practice,particularly where the pregnant liquor can bepumped to the precipitation section of an existingmetallurgical plant. Usually no specialconsideration is given to the preparation of the minedump for leaching, and in fact the decision to leachoften comes after the dump was laid down. Whereit is possible to plan ahead for leaching, thefollowing operations are standard practice:

1. All vegetation is removed over the dump area.2. The surface of the dump area is compacted

and overlain by impervious material such as clay.3. Fine material should be separated.4. A long, narrow dump may be desired to

promote natural aeration.5. The surface of the dump is ripped, or otherwise

uncompacted.6. The dump material may be moistened as it is

laid down, inducing oxidation while the material isstill in direct contact with atmospheric air.

7. The dump may be leached in a series of “lifts,”which has been found to be more efficient thanattempting to leach the entire waste dump in asingle operation.

Heap Leaching.—Heap leaching is applied toores where the grade is too low to pay for haulage,conventional concentration, or leaching in a vatoperation. Complex ores that cannot be treatedeconomically by conventional processes may be

mined and heap leached. The techniques are nodifferent than for leaching mine dumps, except thatthe operation is totally planned, and theprecipitation plant is often specifically designed forthe purpose, rather than being a section of the plantat a conventional metallurgical operation. Heapleaching has been applied mainly to low-gradecopper and uranium mineralization, although thereis presently much interest in the method forprecious metals.

Ore DressingAt most modern mining operations, whether

surface or underground, the ores are not rich enoughto ship long distances to smelters, and they aresubjected to milling, mineral dressing, orbeneficiation. All of these terms are sometimesreferred to as ore dressing. Ore dressing is themechanical separation of the grains of ore mineralsfrom the worthless gangue. The resultingconcentrate contains most of the ore minerals, andthe waste is called tailings.

Crushing and ConcentrationUsually two stages of crushing are used in ore

dressing because it is more efficient than crushingto a relatively small size in a single stage operation.First stage, or primary, crushers are usually jawcrushers in small operations and gyratory types inlarger operations. Primary crushers and the coarseore bins may be located at the mine, where the mineand mill operation are separated. Secondarycrushers and the fine ore bins are usually at the mill,along with blending or custom facilities where morethan one kind of ore is mined or received. The fineore is ground in ball or rod mills to a size smallenough to liberate the ore minerals, then classifiedin various kinds of machines to insure that the feedto the mill is uniform.

The various ore dressing methods are based onphysical characteristics such as density, wettability,chemical reactivity toward certain reagents, andmagnetic characteristics.

Flotation.—Flotation is the most widely usedmethod of beneficiating complex and low-gradesulfide ores in the western United States. The word“concentrator” is virtually synonymous with frothflotation plant. The crushed, ground, and classified

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ore is pulped with water, and special reagents areused to make one or more of the ore minerals waterrepellent and responsive to attachment with airbubbles. As the desired minerals are buoyed to thesurface by the attached air bubbles, they areremoved by mechanical paddles as concentrate,leaving the other minerals behind. Often severalstages of flotation with selective reagents areemployed to obtain the desired concentration.

Pneumatic, or air, flotation cells are long, opentroughs through which the pulp flows, and gasbubbles are introduced from the bottom toaccomplish agitation and frothing. Mechanical cellsare boxlike and are agitated by a rotating impellerthrough which air bubbles are introduced.

Gravity.—Gravity methods of concentration arebased on the simple fact that the ore minerals areheavier than the gangue. Gravity may be the solemethod of concentration, or the equipment may bea part of the mill “flow” scheme, where wastematerial is separated in a series of steps. The jig is aboxlike apparatus containing a submerged screenthat supports a bed of ground ore. The ore is stratifiedby the action of two pulses of water, one upward,downward, alternating in rapid succession. Duringthis pulsation, particles of different density arrangethemselves according to size and specific gravity, thetailing forming the top layer, a fine concentratepassing through the screen, and a coarseconcentrate forming in a layer on the screen.

Shaking tables are inclined, elongated deckswith cleats nailed to the surface. The table isvibrated lengthwise with a slow motion in onedirection and a rapid return. A thin layer of waterflows down and over the deck, and slurry feed isintroduced at the upper corner. Small, heavy par-ticles ride high on the table, parallel to the cleats, tothe end where they are collected. Light materialwashes over the cleats, down to the lower sidewhere it spills over into a trough and is directedtoward the tailings disposal area.

Where heavy, insoluble minerals are involved, aliquid of specific gravity intermediate between oreand waste can be used to make the separation inthe process called sink-float. The ore need bebroken only fine enough to separate ore mineralsfrom waste, and in some deposits this means

simple screening of the material as it comes fromthe mine, breaking oversize to 6 inches or more.Low-grade barite ores have been economicallyupgraded using the sink-float process, and themethod has found application in upgrading coal.

Magnetic Separation.—Approximately 20 oresare magnetic enough to be separated by themagnetic process. The separation can be eitherwet or dry. In one wet process, magnetic drumseparators are used to lift the magnetic particlesfrom a stream of ore pulped with water. In a typicaldry process, the magnetic particles are lifted fromthe moving stream of ore by a fast moving magneticcross belt.

Extractive MetallurgyExtractive metallurgy involves the recovery of

metals and metal compounds from ores andmineral concentrates. Pyrometallurgy,hydrometallurgy, and electrometallurgy are theprincipal methods involved. As these names imply,heat, aqueous solutions, and electric current areused to produce metals and metallic compounds ofsufficient purity for the market.

Pyrometallurgy.—Electrical energy is used orfuels are burned to apply sufficient heat inrefractory-lined furnaces to melt the charge of oreor mineral concentrate in the pyrometallurgicalprocess. Some minerals are volatilized at elevatedtemperatures and can be recovered by distillationfrom kilns, furnaces, and retorts. Other metals canbe separated by liquation, using differences inmelting point.

Smelting is by far the most important of thepyrometallurgical processes. The ore and wasteminerals are heated, altered, fluxed, or reduced toform a low-density slag and one or more liquidmetals. Only high-grade ores or concentrates canbe smelted because of the high cost. It is usuallynecessary to further refine the metal to a product ofacceptable purity.

All pyrometallurgical operations produce largevolumes of gas containing a wide variety ofvaporized metals, dust, and fumes. Many smeltersare large centralized installations that havegradually evolved over the years at some majorseaport, rail point, or other shipping center. Only ina rare situation would a smelter be planned near asingle mining operation in a region with relativelypoor transportation facilities.

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Hydrometallurgy.—Hydrometallurgical processesselectively dissolve metals from ores andconcentrates, resulting in recovery of relativelypure metal. Various acids, such as sulfuric acid,and alkaline solvents, such as the hydroxides andcarbonates of sodium or ammonium, are popular inleaching ores. Sodium and calcium cyanidesolutions are widely used in extracting gold andsilver from precious metal ores.

The usual technique is to agitate finely groundore or concentrate in open vessels at atmosphericpressure. Vat leaching percolates crushed orebedded in large, stationary, rectangular, or circularcontainers. There is presently much interest inthese processes, because many ores that wereformerly smelted may be treated byhydrometallurgy with far less air pollution andconsumption of energy.

Electrometallurgy.—Two kinds of electro-metallurgical processes are in general use today. Inone, the electric current is used as a source of heat;in the other, the current is used in electrolyticdeposition on cathodes. Electrical heating issubstituted for fuel heating where precise control oftemperature is required, or the atmosphere of thefurnace or purity of the metal is of concern.

Electrolytic processes include two generalmethods, one using an aqueous electrolyte, theother a fused salt electrolyte maintained at hightemperature. The aqueous electrolyte method iswidely used to purify metal produced bypyrometallurgical methods.

WastesSome high-grade ore deposits are so massive

and so easily distinguished from wall rock that theycan be removed by highly selective miningmethods underground. A moderate amount of wasterock produced during development ofhaulageways through barren wall rock can often bedisposed of as stope fill with the result that there areno large waste dumps at the surface. More often, aconsiderable amount of barren or low-gradematerial is taken from the mine during explorationand development, and disposal of broken waste

rock on the surface is a major problem.

Mine WastesIn mountainous terrain, particularly wheredevelopment is by adit and where access is difficult,waste dumps are located in or near the streambottoms. Normally, waste is dumped just beneaththe level of the adit portal or shaft collar.

Where a reservoir may be desired as a source ofwater for mine, mill, and town site, it may bepossible to locate the mine waste dump so as toimpound water. Many such reservoirs havebecome important recreational assets foremployees and the public.

There is no general fixed ratio for the amount ofwaste produced compared to ore, but in most casesit is less than 1:1 waste:ore in underground miningoperations. At certain points in the development ofbulk mining operations, such as block caving, forbrief periods virtually all of the material taken fromthe mine will be waste rock. Shafts for ore haulagesystems may deliberately be laid out well away fromthe ore body in waste rock to insure that thesefacilities will not be damaged or destroyed bymining.

Open pit operations, such as phosphate andcopper, produce far more waste rock thanunderground methods, and disposal of this materialis a major aspect of the operation. It is common forthe ratio of waste to ore to exceed 1:1, and in somecases in tons or more of waste are removed foreach ton of ore taken from the pit.

In the large view, some planners see major openpit mines as a solution to the surface disturbanceproblem. They are efficient and highly productive ofmetal, concentrating disruption in one local arearather than having the same production come fromtens or hundreds of smaller operations scatteredthrough the region. For example, in Nevada, onesmall cluster of open pit copper mines, embracingan area of several square miles, has producedmore copper and molybdenum than all of the othermines in the State combined, by a very widemargin.

As in other kinds of surface reclamation, it isusually much more economic to plan the best wastedisposal before the material is placed. Satisfactorysolutions can often be worked out beforehand at an

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acceptable increase in operating cost, particularlywhere the solution can be coordinated with otherphases of the operation, such as providing asuperior yard facility for the machine shops or betterlayout of a mine dump leaching operation.

There is a certain amount of noise pollution indrilling, blasting, movement of large equipment,and the operation of air compressors, powerplants,crushers, and mills. This noise usually affects onlythe people in the immediate area of the mine andmill, who are employees of the operation. Mostmine operators are attempting to reduce noisewherever possible, in line with recent industrialsafety studies, which show that worker fatigue canresult from noisy environments.

The water draining from newly opened orabandoned mines can have a major impact upon theenvironment downstream. Solid particulate mattermay be introduced in sizes ranging from fine silt tosand, and consisting of relatively inertmaterial, although chemical reactions may convertsome or all of it to more soluble chemicalcompounds. Radioactive material may be involved insome cases, and organics may be introduced intosurface waters. Mine waters are often “acid” becauseof the common association of the iron sulfide pyritewith most metal ores and many solid fuels. Pyrite, aswell as a number of other ore and gangue minerals,rapidly decomposes when broken and in contact withmoisture and air, producing sulfuric acid. Thischemical reaction proceeds spontaneously, and theacid mine water then has the ability to take otherpollutants into solution.

Mines where broken or ground pyritic materialhas been used as stope fill are particularly likely toproduce acid water; it is possible to minimize this tosome extent by shutting off this portion of the mine,or otherwise keeping the supply of oxygen andmoisture from these areas. Alternatively, a minecan be partially or entirely flooded with water toeliminate oxygen.

When it becomes necessary to reopen old mines,they are often found to be partially flooded with acidwater containing much dissolved material. It maybe possible to gradually release such water intosurface drainage during the runoff season. Sudden

release during low water would cause majorenvironmental damage. It is sometimes possible totreat mine water by various processes beforereleasing it, as for example neutralization of acid byusing lime or caustic soda. Mine water may be useddirectly in the mill boilers, where it may be recycledto further reduce contamination of surface water.

Some mine water is of sufficiently good quality tobecome an important local source andenvironmental asset.

Mill WastesBecause most mill wastes are finely ground and

are moved to disposal areas in a water slurry,particular problems are encountered with theenvironment. In many milling operations the oreconstitutes only a small portion of the materialrecovered as concentrate. For example, only 2 or 3percent of the weight of ore in a low-grade coppermine ends up as concentrate. The 97 to 98 percentwaste must be disposed of as mill tailings, whichare directed through ditches, launders, and pipesystems to pond disposal areas downhill from themill. In some cases, mill tailings can be classifiedand returned underground to be nozzled underpressure as stope fill.

Mill tailing ponds are usually impounded behindembankments built from the tailing material itself.Sometimes it is necessary to install drainagesystems beneath the dam and pond area tofacilitate drainage where the natural ground is notsufficiently porous. The site should be selected sothat surface water cannot erode the toe of theembankment. It is usually necessary to construct acatchment pond downstream from theembankment to collect seepage water and tailingseroded from the face of the embankment. Decantsystems take off the water after solids haveseparated, and the floor of the pond gradually risesas disposal continues. A major threat to the tailingspond is overflow of the embankment due to floodingin the drainage system above the tailings.Abandoned, poorly designed tailings ponds arequite troublesome in this regard, particularly whereno attempt was made to stabilize the surface, or todivert surface water away from the area.

When the surface of an unstabilized tailings pondis allowed to dry, major pollution of the nearby areacan occur when fine particles are picked up by thewind. Proper location, design, and operation of the

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disposal system minimizes some of the difficulties.Again, old abandoned tailings are often a majorproblem.

Dissolved metals and salts, in highly toxicsolutions, are sometimes found leaching from milltailings. Modern practice is to remove this materialwhere it is at all feasible to do so.

Miscellaneous JunkIn many of the old mining camps of the West,

every trace of former mining activity has beenremoved by scavengers to the point that the exactposition of some small districts of historical recordcan no longer be found with certainty. In someareas of more recent activity, for example the goldmines of the 1930’s and tungsten mines of the1950’s, the mine buildings and equipment are lessromantic, gradually having fallen into a state ofvandalized disrepair that in every way qualifiesthem as the prime local eyesore. Eventually, all ofthe iron will be taken for scrap, the tanksappropriated by local ranchers and farmers, andthe wood and galvanized sheeting hauled away. Inthe meantime, there is often little that can be doneto quickly clean up these areas, unless some localregulation permits them to be classified as estheticnuisances or safety hazards.

If a considerable amount of junk has been left ina district or group of districts, it may be possible toarrange for outside scrap collectors to makecontact with the owners for a bid on salvage.Caution should be exercised, however, for theseold facilities sometimes are classified as genuineantiquities at about 50 years of age, and publicsentiment may be very much divided as to the meritof removal.

In presently operating mines, or newly plannedoperations, it is possible to insure removal of thesurface plant and equipment. There are problems,however, with the law insofar as the rights tostructures on lands optioned or leased from privateindividuals that may for one reason or anotherrevert to original ownership.

RoadsIn most cases, where public funds are used for

road construction and maintenance, the public mayhave some use of the roads. This may abruptlyterminate at the mine property boundary, and agatekeeper may allow entry only to company

employees or people having legitimate business onthe property. There are a number of reasons whymining companies do not permit people to enter theproperty at will. An unsuspecting tourist couldeasily drive off an open pit bench, fall into a tank fullof solution, or become involved in any one of ahundred other industrial hazard situations.Exposure to public liability alone is enough to makemost companies enclose the mine and mill area inchain link fence.

Many companies recognize the damage to theirpublic image when the typical curious tourist maysuddenly be confronted with a curt rebuff at the endof a well-traveled and maintained road, and thoughtis usually given to minimizing the effect. Most openpit operators arrange guided tours or self-guidedvantage points where the visitor can gain a clearperception of the mine operation, yet stay at adistance where he will not be in the way or exposedto any risk. Mine tours and viewpoints engender agreat amount of good will for the mining industry,and go a long way toward eliminating a potentialsource of friction between mine operator and thepublic.

Many mine operators recognize that facilitiessuch as reservoirs, or the drainage system behindthem, that provide water for mine, mill, and townsitehave a considerable recreational potential foremployees. Because local fish and gameauthorities will not usually stock or manage gameon private lands from which the public has beenexcluded, and because of probable adverse publicopinion if the areas are restricted to employee use,such recreational areas are often opened to thepublic, with the normal restrictions of a privatelandowner. More than the usual number of signscautioning potentially hazardous situations areposted, because of the private landowner’sexposure to possible liability. Companies havebeen known to subsidize or entirely finance boatlandings, beaches, parks, camping facilities, andski lifts and lodges, and have been involved in gamemanagement programs, such as stocking of fishand reintroduction of game animals, where suchprojects would not be economically sound for aprivate individual.

The public is allowed use of mine access roads torecreational areas. There are sometimes unusualtraffic controls, rights-of-way, and traffic movement

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patterns. One-way traffic may be necessary atcertain times on narrow roads where largeoff-highway units are used. Water trucks maydissipate dust almost continuously to improvedriving safety and to reduce wear on truck bearingsand engines. On unsurfaced haulage roads wherelarge trucks are used, the traffic flow is oftendirected so that loaded trucks are against the hillrather than out on the bank, where the weight of theload may break the edge of the road down, andwhere the driver might experience difficulty if he

were to suddenly lose control. This results in aconsiderable amount of travel on the left side ofopen pit haul roads.

When a road has been constructed by the ForestService for Forest purposes, the miner who desiresto use it may be required to share the cost ofmaintenance, based perhaps upon a ton per milefee for the miner’s proportional use of the road. Theminer may be required to maintain or help tomaintain such a road in the condition it wasoriginally designed for.

There is a widespread public feeling that themining industry has defaced vast areas; this beliefprobably in part originates because roads and othertransportation facilities are well-developed inestablished mining areas. The area affected bymining is about a sixth that devoted to highways,and is approximately equal to that used for airportsin this country. In terms of benefit to the Nation,mining is essential and in all fairness modern,well-planned and operated mines are not thedespoilers many believe them to be.

Over the years, the increased size and efficiencyof powered excavation equipment and improveddrilling end blasting techniques have resulted invery low cost mining operations. As the individualand total number of these bulk mining operationshave grown, so has public interest in reclamation ofthe surface disturbance resulting from them. ManyStates now require land reclamation as an integral

part of mine planning. A large percentage of minedland is now being reclaimed, or at least partiallyreclaimed to an acceptable condition.

Extensive research is being conducted by miningcompanies, several Government agencies,including the Forest Service through its SEAMprogram, and university scientists on the manytechnical facets of reclamation. Results are beingshown at demonstration areas, and are beingrapidly incorporated into mine planning andcontinuing operations.

This brief chapter makes no attempt to discussthe many technical facets of reclamation. Rather, itbriefly presents several general concepts.

Satisfactory reclamation should emphasize threemajor objectives:

1. The productivity of the reclaimed land should atleast equal that of the premine surface. This doesnot necessarily mean that the site must be restored

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to an approximation of its original condition, or thatsurface uses after mining will be the same as thoseexisting prior to mining. For example, an area usedfor marginal grazing prior to mining may be changedto a useful and attractive recreational complex, orperhaps in another case to a housing area.

2. Satisfactory reclamation should leave the minedarea in a condition that will not contribute toenvironmental degradation either in the form ofair- or water-borne materials, or from chemicalpollution.

3. The reclaimed area should be estheticallyacceptable and it should be safe for the usesintended.

Reclamation goals must not only be technicallyfeasible, they must be economically attainable. Insome cases restoration to the original contour is notpractical. For example, in a major open pit copperoperation, 500 million tons of ore are mined andsent to the mill, and a billion tons or more ofoverburden will be placed on waste dumps. Millingwill result in almost 500 million tons of tailings, and10 to 15 million tons of concentrate that will beshipped to the smelter, and from which 5 milliontons of copper metal will be recovered. Theexcavation of a billion and a half tons will leave ahole nearly a cubic mile in size. Using presentlyavailable mining methods, particularly at minesalready partially developed, it is not possible toeconomically replace the mine and mill wastes and

to restore the surface to anything like the originalcontour. Planning must take the reality of thesituation into account and aim toward possibleultimate benefit to be derived from a surfaceconfiguration much different than prior to mining.

There are no cut and dried standard formulas foraccomplishing reclamation. Almost every casediffers and is influenced not only by naturalvariables such as climate and the material to beworked with, but by social variables such as thelaws of the particular State where the operation islocated, the ownership of the land, and the goalsthe public may wish to see pursued throughreclamation. In addition, the operator’srequirements as to methods of mining and timingwill affect the final decision concerning specificprescriptions for reclamation.

Mining companies now generally have expertiseavailable for planning reclamation. Land managerscan be of assistance by participating in the planningprocess and by contributing technical knowledgewhere possible and where needed. Assistanceoften can be given on specific information such asplant and wildlife species, seeding methods, laborsources, and plant material sources. The finaldecisions on reclamation will most often be the resultof the combined contributions from many sources,both public and private. Reclamation ideally is justanother end result of thorough mine planning.

Federal Recycling Program Printed on Recycled Paper

U.S. Department of Agriculture, Forest Service. 1995. Anatomy of a mine from prospect toproduction. Gen. Tech. Rep. INT-GTR-35 revised. Ogden, UT: U.S. Department ofAgriculture, Forest Service, Intermountain Research Staion. 69 p.

Reviews mining laws and regulations and their application to mining in Western States.Describes prospecting, exploration, mine development and operation, and reclamationfactors.

Keywords: mining law, mineral exploration, mine development, mine operation, mining areareclamation

The Intermountain Research Station provides scientific knowledge and technology to improvemanagement, protection, and use of the forests and rangelands of the Intermountain West. Researchis designed to meet the needs of National Forest managers, Federal and State agencies, industry,academic institutions, public and private organizations, and individuals. Results of research are madeavailable through publications, symposia, workshops, training sessions, and personal contacts.

The Intermountain Research Station territory includes Montana, Idaho, Utah, Nevada, and westernWyoming. Eighty-five percent of the lands in the Station area, about 231 million acres, are classifiedas forest or rangeland. They include grasslands, deserts, shrublands, alpine areas, and forests. Theyprovide fiber for forest industries, minerals and fossil fuels for energy and industrial development, waterfor domestic and industrial consumption, forage for livestock and wildlife, and recreation opportunitiesfor millions of visitors.

Several Station units conduct research in additional western States, or have missions that are nationalor international in scope.

Station laboratories are located in:

Boise, Idaho

Bozeman, Montana (in cooperation with Montana State University)

Logan, Utah (in cooperation with Utah State University)

Missoula, Montana (in cooperation with the University of Montana)

Moscow, Idaho (in cooperation with the University of Idaho)

Ogden, Utah

Provo, Utah (in cooperation with Brigham Young University)

Reno, Nevada (in cooperation with the University of Nevada)

The policy of the United States Department of Agriculture Forest Service prohibits discrimination onthe basis of race, color, national origin, age, religion, sex, or disability, familial status, or politicalaffiliation. Persons believing they have been discriminatedagainst in any Forest Service related activityshould write to: Chief, Forest Service, USDA, P.O. Box 96090, Washington, DC 20090-6090.

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