Limestone and dolomite constitute a group of raw materials com-monly referred to as carbonate rocks. They represent the basicmaterials from which cement, lime, most building stone, and a sig-nificant percentage of crushed stone are produced. Carbonate rocks,and their derived products, are used as aggregates, fluxes, glass rawmaterial, refractories, fillers, reactive agents in sulfur-oxideremoval, abrasives, soil conditioners, and in a variety of other mar-ket applications, many of which are covered in this edition.

Carbonate rocks form about 15% of the earths sedimentarycrust and are widely available for exploitation. Found extensivelyon all continents, they are quarried and mined from formations thatrange in age from Precambrian to Holocene. Reserves of carbonaterock are large and will last indefinitely, although high-purity depos-its may be absent or have limited availability in certain states andregions.

Limestone and dolomite are so useful and so abundant that in2002 about 1.6 billion t were produced in the United States. In fact,about 71% of all stone quarried or mined in the United States wascarbonate rock. Sand and gravel was the only mineral commodityproduced in greater quantity.

This chapter is an overview of carbonate rocks and their com-position, distribution, production, and uses. The literature on lime-stone and dolomite resources of the United States and Canada is sovast and diverse that one can easily become mired in print. The581

authors have tried to list those references that are easily accessibleand serve as a starting point for more intensive study. Additionally,

Table 1. Physical properties of some common carbonate minerals

Mineral Physical Properties

Calcite (CaCO3) Hexagonal crystal system, commonly good cleavage. Mohs hardness, 3; specific gravit

Dolomite (CaCO3MgCO3) Hexagonal crystal system, commonly good rhowith curved faces. Mohs hardness, 3.54.0; s2.87.

Aragonite (CaCO3) Orthorhombic crystal system. Mohs hardnesspecific gravity, 2.932.95.

Siderite (FeCO3) Hexagonal crystal system, commonly distortcrystals. Mohs hardness, 3.54.0; specific g

Ankerite (Ca2MgFe(CO3)4) Hexagonal system, commonly rhombohedrahardness, 3.54.0; specific gravity, 2.9.

Magnesite (MgCO3) Hexagonal, usually in granular or earthy masse3.54.5; specific gravity, 2.963.1. the selected references on limestone and dolomite resources in Can-ada and the United States reflect the effort to be selective ratherthan exhaustive and to direct the reader to the best sources ofdetailed information. The reader is also referred to other chapters inthis volume that provide additional information on limestone andits uses, including the chapters on Lime and various chapters onConstruction Uses.

GEOLOGYMineralogyLimestone and dolomite are the principal carbonate rocks used byindustry. Limestones are sedimentary rocks composed mostly ofthe mineral calcite (CaCO3), and dolomites are sedimentary rockscomposed mostly of the mineral dolomite (CaCO3MgCO3). Ara-gonite (CaCO3), which has the same chemical composition as cal-cite but a different crystal structure, is economically important onlyin modern deposits such as oyster shells and oolites. Aragonite ismetastable and alters to calcite in time. Some other carbonate min-erals, notably siderite (FeCO3), ankerite (Ca2MgFe(CO3)4), andmagnesite (MgCO3), are commonly found associated with lime-stones and dolomites but generally in minor amounts.

Because of their similar physical properties, the carbonateminerals are not easily distinguished from one another. Specificgravity, color, crystal form, and other physical properties (seeLimestone and DolomiteRobert C. Freas, John S. Hayden, and Charles A. Pryor Jr.Table 1) are aids to mineral identification if the rock is relativelymonomineralic and compact. Further information on the chemical,

Common Color

rhombohedral y, 2.72.

Colorless or white but may be other colors because of impurities

mbohedral crystals pecific gravity,

White or pink

s 3.54.0; Colorless, white, or yellow, but may be other colors because of impurities

ed rhombohedral ravity, 3.73.9.

Brown or black

l crystals. Mohs White, pink, or gray

s. Mohs hardness, White or yellowish but may be other colors because of impurities.

er582 Industrial Min

mineralogical, and physical properties of carbonate minerals canbe found in Graf and Lamar (1955) and Tucker and Wright (1990).

The rate of solubility of the different carbonate minerals indilute hydrochloric acid is perhaps the most useful technique toidentify them in the field. Calcite is much more soluble in diluteacid than dolomite; hence, if a fresh rock surface is etched, theamount of dolomite left standing in relief can be estimated using ahand lens. Some staining techniques are based on differences in sol-ubility of the carbonate minerals (in decreasing order of solubility:aragonite, calcite, and dolomite). These staining techniques are use-ful in the laboratory but have limited application in the field (Fried-man 1959; Warne 1962). Thin-section staining is particularlyeffective in the laboratory (Dickson 1965, 1966).

The x-ray diffractometer is commonly used in the laboratory fordetermining carbonate mineralogy of bulk samples. Cullity (1956),Azaroff and Buerger (1958), Gulbrandsen (1960), Graf and Gold-smith (1963), Muller (1967), and Runnells (1970) describe tech-niques for determining calcite and dolomite ratios or the percentageof these minerals based on comparison of their diffraction intensitieswith those of known standards.

Thin-section analysis may be a helpful adjunct to binocularexamination of carbonate rocks. Although it is difficult to distin-guish between calcite, dolomite, and ankerite in thin section unlessstaining techniques are used, identification of other minerals, typesof carbonate grains, fabrics, textures, and structures is sometimesfacilitated by this method (see also section on Physical Properties inthis chapter). Appropriate parts of Carozzi (1960) and Hatch andRastall (1971) introduce microscopic investigation of carbonaterocks, as does the review by Gubler et al. (1967), and Adams andMacKenzie (1998). Good references for assistance in identifyingfossils and fossil fragments in thin section are Horowitz and Potter(1971) and Scholle (1978).

Color, an important property of carbonate rocks, can be arough guide to purity, but it also can be misleading. Only a smallamount of noncarbonate material is necessary to produce a markedchange in color. The famous building stone called Indiana Lime-stone, for example, with its distinct gray and buff colors, commonlycontains less than 0.2% Fe2O3 (iron oxide). Carthage Marble, a fos-siliferous dimension limestone from Missouri in shades of gray,generally has a total iron and aluminum oxide content of less than0.2%. Limestones in shades of gray or green generally indicate thepresence of minerals containing iron oxides or carbonaceous mat-ter. As the state of oxidation increases, the colors change to yel-lows, browns, or reds. A color reference chart is useful inmaintaining uniformity of rock descriptions, and one of the mostuseful is available from the Geological Society of America (God-dard et al. 1963).

Impurities in carbonate rocks vary considerably in type andamount but are important from an economic standpoint only ifthey affect the usefulness of the rock. Generally, the two mostimportant considerations of each impurity are how much is presentand how it is distributed. A considerable amount of some impuri-ties is tolerable in carbonate rock for some uses if the impurity isdisseminated throughout the rock. But if the impurity is concen-trated in laminae, it may form planes of weakness that seriouslyaffect the performance of the rock.

Clay is perhaps the most common impurity in carbonaterocks. The clay minerals, mainly kaolinite, illite, chlorite, smectite,and mixed-lattice types, may be either disseminated throughout therock or concentrated in laminae or thin partings. The basic molecu-

lar building blocks of clay minerals are silica tetrahedra (a siliconatom and four oxygen atoms) and alumina or magnesium octahedra(an aluminum or magnesium atom and six hydroxyl ions). Otherals and Rocks

chemical elements are incorporated into the structure, however, soit is difficult to determine the type of clay mineral by chemicalanalysis alone. If clay mineral identification is important, otheranalysis techniques such as x-ray diffraction, differential thermalanalysis, and electron microscopy can be used. The clay chapters ofthis volume give a comprehensive review of clay minerals.

Chert is another common impurity in carbonate rocks and canbe disseminated as grains throughout the rock or concentrated innodules, lenses, or beds. It is composed mainly of very fine grainedquartz (SiO2) that may appear under the microscope as minute sub-equant crystals, usually 1 to 10 m in diameter (microcrystallinequartz), or as radiating fibers (chalcedonic quartz). Chert easilyincorporates impurities, including water, into its structure so that itcan be found in almost all colors; its surface texture can range fromdense or porcelaneous to porous or earthy. Dense cherts have aMohs hardness of 7 and high impact toughness, which make themparticularly abrasive to crushers and other processing equipment.Porous cherts, mainly because of their large surface area availablefor chemical reaction and moderate solubility in alkalies, are consid-ered deleterious components in aggregates used in concrete. Dunnand Ozol (1962) give comprehensive coverage of the deleteriousproperties of cherts.

Silica is also found in carbonate rocks as discrete silt- or sand-size grains of the mineral quartz. These grains may be disseminatedthroughout the rock or concentrated in laminae and beds. Detritallimestone especially may contain a considerable percentage ofquartz silt and sand. These grains can act as the nuclei for coatedcarbonate grains, such as some ooliths and pisoliths.

Finely disseminated organic matter is a common constituentof limestones and dolomites and can give the rock a pronouncedbrown or black color. Bituminous material, an organic derivative ofpetroleum and residue of former pore fluids, can be present in suffi-cient quantity to make the rock undesirable for some uses.

Thin-section and insoluble-residue studies reveal traceamounts of a wide variety of other minerals in most carbonaterocks. Although these trace minerals may affect the economic use-fulness of rocks used for chemical purposes, such as glass manufac-ture, they have little effect on rocks used principally because oftheir physical properties, as in construction materials.

OriginMost limestones of economic importance were partly or whollybiologically derived from seawater and accumulated in a relativelyshallow marine environment. The obvious skeletal material in lime-stones speaks of a biologic origin, but even nondescript, fine-grained material may derive from the life of organisms. Pellets inmany instances are fecal material, and silt- and clay-size particlesmay be aragonitic-sheath crystals released upon the death of algae.Ooliths, which in the past have largely been thought to be the inor-ganic accumulation of calcium carbonate around a nucleus, mayalso depend in part on algal activity.

In some places, lime-secreting organisms such as corals, cal-careous algae, and mollusks erect large, wave-resistant structurescalled reefs. The biologically active parts of these structures aregenerally near the edge of shallow marine shelves where upwellingcurrents supply nutrients for the growth of the organisms. In otherplaces along such shelves, small skeletal particles or other materialcan become coated by concentric layers of calcium carbonate toform ooliths. Oolites develop best in the high-energy zone ofshelves where water currents agitate the grains, and as the oolitesbuild up they form elongate lenticular bars that nearly reach the

water surface. Very fine grained carbonate muds (micritic lime-stone) derived from the comminution of coarser skeletal material

aLimestone

or precipitated directly from seawater, accumulate in low-energyenvironments such as lagoons or deep water.

The depositional environment is significant because it deter-mines the size, shape, purity, and other economically significantcharacteristics of the carbonate rock deposit. Limestones that formin high-energy zones generally contain little noncarbonate materialand hence may be the source of high-purity carbonate material.Micrite, which accumulates in zones of low energy, is more likelyto be diluted by clay and silt-size noncarbonate material.

Carbonate sediments are highly susceptible to postdeposi-tional alteration and modification. The origin of dolomite is espe-cially significant to the geologist. Although some dolomite maybe precipitated directly from seawater, most dolomite is a result ofthe alteration of calcium carbonate sediments or rocks by hyper-saline brines. Good examples are the almost-pure dolomite Sil-urian reefs in northern Illinois, Indiana, and Ohio, and in southernMichigan.

The depositional environment and postdepositional history ofcarbonate rocks are best understood by studying modern carbonatedeposition. The general reviews by Baars (1963), Ginsburg et al.(1963), and Milliman (1974) are good references for this informa-tion. For further information on locations and distributions of mod-ern carbonate sediments, the summaries by Graf (1960a, 1960b,1963) are useful; the comprehensive discussions of the origin andoccurrence of carbonate rock in the papers compiled by Jordan(1978) and Scholle, Bebout, and Moore (1983); in the book by Wil-son (1975); and the reviews of limestone by Sanders and Friedman(1967) and of dolomites by Friedman and Sanders (1967) fill thegaps of the other coverages. Tucker and Wright (1990) providegood coverage of carbonate sedimentology.

ClassificationThe explosive growth in the study of modem carbonate sedimenta-tion from the late 1950s to the present has had a notable effect oncarbonate rock classification. Numerous classification schemeshave emerged based on this new-found information, such that car-bonate rock descriptions are now more explicit and more conduciveto genetic interpretation than ever before.

Many aspects of carbonate rocks can be used as the basis of aclassification scheme, but perhaps the most useful are compositionand texture. Composition can be thought of in terms of mineralogy,types of fossils or grains, or chemical constituents. Texture refers toboth depositional and postdepositional features such as relative pro-portions of framework grains and lime mud, grain size, cement, andpores.

Carbonate rocks are rarely monomineralic in nature; thus, amineralogical classification of these rocks needs to consider varia-tion in amounts of calcite, dolomite, and noncarbonate materials(see Figure 1). Such a classification is useful in rock descriptions,especially when combined with textural parameters, but it com-monly is not sufficient for industrial purposes. Although limestoneand dolomite can be used equally well for many purposes, certainuses have special chemical requirements. These special require-ments are stated in terms of chemical composition rather than min-eralogical composition and specify the quantity of CaCO3 (or CaO,calcium oxide) and MgCO3 (or MgO, magnesium oxide) or both inthe rock along with the maximum percentage of impurities that canbe tolerated. A practical chemical classification considers that ultra-high calcium limestone is more than 97.5% CaCO3, high-calciumlimestone is more than 95% CaCO3, high-purity carbonate rock ismore than 95% combined CaCO3 and MgCO3, and high-magne-

sium dolomite is more than 43% MgCO3 (theoretically pure dolo-mite is 45.7% MgCO3).nd Dolomite 583

A textural classification as well as a mineralogical classifica-tion is fundamental to geologic studies to determine the origin ofcarbonate rocks. One such classification by Leighton and Pendex-ter (1962) considered that most limestones can be characterized bythe types and relative amounts of four textural components: grains,lime mud (micrite), cement, and pores. The ratio of relative pro-portions of grains to micritic material, which is the basis of theirnomenclature system (Table 2), gives some indication of water tur-bulence because muds cannot be deposited in areas with strongbottom currents. Other classifications, such as the ones by Folk(1962; see Table 3) and Dunham (1962; see Table 4) make use offramework grains to mud ratios and have practical applications.

Dolomite presents a special problem in classification and mayrequire separate handling from limestone. The textural classifica-tion can be used for secondary dolomite if the original depositionaltexture is preserved. Some dolomites, however, show only fainttraces of original texture, called ghosts or relics, and others mayhave had their original texture completely obliterated. For thesecases, and for dolomite of primary origin, a classification based oncrystal size may be required.

Distribution of DepositsCarbonate rocks have been deposited from Precambrian toHolocene time, and although they compose only about 0.25% of thevolume of the crust of the earth (Parker 1967), they comprise about15% of the sedimentary rocks. In 2002, limestone and/or dolomitewere quarried or mined in all of the 50 states except Delaware, Lou-isiana, New Hampshire, and North Dakota; they were mined in allCanadian provinces except Saskatchewan.

Because carbonate rocks are widely distributed and differ intheir geologic characteristics, each deposit must be considered onits own attributes. The best source of information for carbonaterock deposits is the state geological surveys, or their equivalents.Most state publications are oriented toward aerial geology, com-modities, or the two combined, rather than uses or methods. TheU.S. Geological Survey (USGS) publishes information on lime-stone and dolomite. The annotated bibliographies of Gazdik andTagg (1957) on high-calcium limestone deposits and of Davis(1957) on some high-magnesium dolomite deposits are helpful

Figure 1. Mineralogical classification of carbonate rocks

Impure Limestone

ImpureCalciticDolomite

ImpureDolometicLimestone

Impu

re D

olomi

te

50% 50%

NoncarbonateRock

Dolomite Calcitic Dolomite Dolomitic Limestone Limestone

Dolomite 90% 50% 90% Calcite

Other Minerals(Mostly Insolubles)guides to the older literature, as is the report on high-grade

ra

n

9

0

edcr

ladolomite deposits by Weitz (1942) and a more recent report byFreas and Horne (1982).

Although high-purity carbonate rock deposits are not overlyabundant, they are by no means rare. All of the states except Dela-ware, Hawaii, Louisiana, Mississippi, New Hampshire, and RhodeIsland, and all of the Canadian provinces, report potentially commer-cial deposits of high-calcium limestone or high-magnesium dolo-mite. A complete list of publications is available on the Web sites ofall the state geological surveys; these Web sites are given later in thischapter and in the bibliography. Twenty-one of the 31 Mexican statesproduced high-calcium limestone or high-magnesium dolomite in2000, and 5 of the Canadian provinces have commercial productionof high-calcium limestone. Because deposits are present, however,does not necessarily mean that they can be exploited. In many areas,competition is intense for potential mineral lands for constructionsites, recreation areas, nature preserves, and highways; even naturehas its own requirements for flowing streams and soil development.Society has also imposed environmental controls, now firmly estab-lished in state and federal statutes, which prohibit or restrict mineralproduction in areas where it might significantly affect the quality ofthe environment.

ExplorationExploration for limestone and dolomite in North America is largely

erable extent. Some data on chemical composition and physicalcharacteristics are available for most such strata in the publishedreports or files of state, provincial, and national geological surveys.Exploration for a new limestone deposit, therefore, in mostinstances begins with a search of these records to find the locationsof deposits that satisfy the various economic factors, and proceedsto a sampling program of favorable deposits. Geophysical tech-niques, if used at all, are performed to determine the thickness ofoverburden. Geochemical techniques are not used.

All aspects of exploration are important, but the one mostlikely to be slighted is sampling. Yet it determines the validity offurther study and may become the basis for hundreds of thousandsand sometimes millions of dollars worth of developmental work.The goal of sampling must be the accurate representation of thelimestone deposit. The most common sampling methods are coring,rock bitting, and surface (ledge) sampling, and the choice amongthese depends on such matters as the geology of the deposit, theproposed use of the material, and the availability of equipment.

Special care should be taken when sampling weathered out-crops. In humid regions, the surface layer of a carbonate rock canbe leached of calcite and dolomite and hence be less pure than therest of the unit. On the other hand, in arid and semiarid regions,where evaporation exceeds precipitation for long periods of time,the surface layer may be enriched in calcite and dolomite. Thus, if

Table 4. Classification of limestones according to the scheme of Dunham (1962)

Depositional Texture

Original components not bound together during deposition Original components were bound together during deposition, as shown by intergrown skeletal matter, lamination contrary to gravity, or sediment-floored cavities that are roofed over by organic or questionably organic matter and are too large to be interstices

Contains mud (particles of clay and fine silt size) Lacks mud andis grain supportedMud supported Grain supported

10% grains

Mudstone Wackestone Packstone Grainstone Boundstone584 Industrial Mine

Table 2. Classification of limestone according to the scheme of Leighto

Grain:Micrite Ratio

%Grains

Grain Type

Detrital Grains Skeletal Grains Pellets

9:1 ~90% Detrital Skeletal Pellet

1:1 ~50% Detrital-micritic Skeletal-micritic Pellet micritic

1:9 ~10% Micritic-detrital Micritic-skeletal Micritic-pellet

Table 3. Classification of limestone using the texture scheme of Folk (1

More than 2/3 Lime Mud Matrix

% Allochems 01 110 1050 >5

Rock terms Micrite and dismicrite

Fossiliferous micrite

Sparsebiomicrite

Packbiomi

1959 terminology

Micrite and dismicrite

Fossiliferous micrite Biomicrite

Terrigenous analogues

Claystone Sandyclaystone

Cthe detailed examination of known deposits. Because most lime-stone is a sedimentary rock, it occurs in strata generally of consid-ls and Rocks

and Pendexter (1962)

Organic Frame Builders

No OrganicFrame-BuildersLumps Coated Grains

Lump Oolitic; pisolitic; algae-encrusted

Coralline; algal

Cal

iche

; tra

verti

ne;

tufaLump-micritic Oolitic; pisolitic;

micriticCoralline-micritic; algal-micritic

Micritic-lump Micritic-oolitic; pisolitic

Micritic-coralline; micritic-algal

Micritic Limestone

62)

Subequal Sparand Lime Mud

More than 2/3 Spar Cement

Sorting poor Sorting good Rounded and abraded

itePoorly washed

biospariteUnsorted biosparite

Sortedbiosparite

Rounded biosparite

Biosparite

yey or immaturesandstone

Submature sandstone

Maturesandstone

Super-mature sandstonesurface samples must be taken under these conditions, the geologistshould be aware of a potential bias.

nLimestone a

CoringCoring is generally the best method of exploring a new deposit. Asingle core may not always be more representative than a sectionsampled in a quarry or in a natural exposure, where some judgmentmay be used as to what is representative, but cores taken on a gridpattern constitute a more representative and unbiased sample of adeposit than an equal number of surface sections. Coring avoidscontamination by soil and weathered material, and disproportionatesampling of different parts of a single unit, yet retains the surfacematerial that may have worked downward into solution cavities.

Initial drilling is generally widely spaced, both to help locate apotential deposit and to determine its potential size. Once an appar-ently large and suitable deposit is discovered, it should be drilled ina more or less regular pattern. The core grid and type of drillingdepend largely on the proposed use of the limestone, although otherfactors such as the homogeneity of the deposit, geologic complex-ity, topography, and cost of drilling are significant. In areas ofsteeply dipping strata, the grid spacing must take into accountwhether vertical or inclined drilling will be used. If the stone is tobe used as cement raw material and the magnesium content of therocks is believed to be marginal and unpredictable, no greater than30-m centers would be required. If the deposit is relatively homoge-neous in one direction and not in another, a rectangular rather than asquare grid might be used. If the stone is to be used as aggregateand is relatively uniform in other deposits, generally only a fewcores need to be taken in several hundred hectares. For most depos-its of flat-lying strata in which the chemical composition of therocks is important, cores should be spaced on 30-m centers until apattern of uniformity indicates that the spacing can be increasedsafely. The authors know of one lime company, quarrying in astructurally complex area of Pennsylvania, that found coring on15-m centers necessary for adequate quality control.

For most limestone exploration, a BX core (4.13 cm in diame-ter) suffices, but if physical tests are required, a core of larger diam-eter must be used. NX core (5.4 cm in diameter) is adequate forchemical analyses and limited physical testing but too small forsome physical tests. If the core is stored for a significant period oftime, it may be necessary to use plastic or wooden core boxes ratherthan the common corrugated cardboard boxes normally supplied bythe core drilling contractor (Figure 2).

Each common physical test of rock used for aggregaterequires about 5 kg of rock. Tests for absorption, abrasion, andsoundness require more than 14 kg of rock. Testing stone for use ashighway materials (ASTM 2004, Volume 04.02; AASHTO 2004)requires a minimum of 23 kg of rock. Highway commissions insome states do not perform physical testing of cores and acceptonly ledge samples. Testing agencies in other states will run physi-cal tests on cores.

Rock BittingUsed alone, drill cuttings are probably the least reliable samples inexploration, but if used to supplement cores or informationobtained from nearby quarries or outcrops, they are an inexpensive,rapid method of acquiring much information. If the drilling is donein a carefully cased hole to prevent contamination by overburden, ifthe cuttings are collected carefully, and if the geologist is experi-enced in interpreting well cuttings, these samples can be as reliableas core and surface sampling for some purposes. In fact, the percus-sion air drill is probably the fastest and least expensive method forpreliminary sampling.Because of the large amount of drilling for oil and gas duringthe past few decades, cuttings of thousands of wells are on file ingovernment and other sample libraries. Although not intentionallyd Dolomite 585

so, these cuttings constitute the largest exploration program forindustrial minerals ever undertaken. Cuttings cannot be interpretedproperly unless the interpreter understands drilling techniques, andthe best interpretation of the well cuttings requires considerablewell-site experience. In addition, the explorationist should be skep-tical of these cuttings without prior knowledge of the drilling condi-tions and the competency of the personnel logging samples fromthese wells. Stein and Starkweather (1996) is a good reference ondrilling and coring.

Surface SamplingChip samples taken carefully on a quarry face can provide a goodrepresentation of the limestone deposit. The geologist should firstinspect the quarry face, divide the face into units of uniformlithology, and then mark tops of units with paint or flags. Thickhomogeneous beds should be arbitrarily subdivided, so that nosample is more than about 1.5 m thick. Starting at the base of theunit, one should take chips of uniform size as nearly as possiblealong a selected vertical line to the top of each unit. (The geolo-gist might start at the top and work down, but it is easier to workup than down.) This method of sampling is sometimes calledchannel sampling. Chip samples should be taken from unweath-ered surfaces even if the weathered rind must be chipped away.Samples should be washed to remove contaminants such aslichens or soil, but care should be taken not to wash out thin,interbedded shales.

Many channel or core samples weigh 5 to 10 kg, and thisamount must be crushed, thoroughly mixed, and quartered severaltimes in the laboratory to reduce the sample to the few gramsneeded for chemical determination.

EVALUATION AND TESTINGIf given sufficient cores or exposures of rock, an experienced indus-trial minerals geologist can evaluate a limestone deposit largely justby visual inspection, using a hand lens, hammer, and weak hydro-chloric acid as the only tools. The geologist can generally appraisewhether a stone will make class A aggregate or cement raw mate-rial. They may not, however, be able to determine whether the stoneis of sufficient purity for other uses. Final evaluation of rocks suit-able for aggregate, dimension stone, and similar uses requires phys-

Figure 2. NX core being placed in a plastic core boxical testing. Rocks used for making lime, cement, or other productsthat depend on chemical purity should be chemically analyzed.

er

ppSpGr

2

2

1

2

2

2

2

2

2

2

2

2

2

2

2

2

2sources: ASTM and the American Association of State Highwayand Transportation Officials (AASHTO). Both organizationsdescribe explicit procedures, in cookbook fashion, for testing lime-stone and dolomite. State highway commissions may specifyslightly different procedures and should be consulted if stone is tobe used as aggregate in those states. In earlier years, several federalorganizations developed physical tests for building stone, such asthose reported by the U.S. Census Office and the U.S. Bureau ofStandards; however, current building-stone testing generally fol-lows procedures outlined by ASTM.

Physical tests are designed to test how well a rock will performfor a particular use. As might be expected, many tests have beendeveloped corresponding to the many uses for which the carbonatemay be designated. Table 5 shows selected physical properties ofcarbonate rock. The Handbook of Physical Constants (Birch et al.1950) and a book by Barksdale (1991) describe a large number ofphysical properties of limestones and other rocks. These referencescontains data on bulk density, compressive strength, compressibilityat high and low temperature, dielectric constant, electrical resistivity,porosity, thermal conductivity, thermal expansion, and other proper-ties that are especially useful to the geophysicist. Manger (1963)published a tabulation of porosity and bulk density determinationsof carbonate rock, as reported in the accessible American, British,German, and Swiss literature.

A great many physical tests of carbonate rock used for aggre-gate have been performed in connection with state and federal road-building programs, but much of this information is unpublished.

tion (NSSGA). ICAR publishes a free reference library of informa-tion on their Web site at www.ce.utexas.edu/org/icar. AASHTO, anonprofit association representing the transportation departments ofall 50 states, the District of Columbia, and Puerto Rico, publishesan excellent two-volume book on aggregate material standards(AASHTO 2004).

Through the years, the U.S. Army Corps of Engineers(USACE) has tested carbonate rock from many quarries in the con-tinental United States to evaluate their potential use in constructinglocks, dams, and other structures. Technical Report No. 6-370, TestData Concrete Aggregates in Continental United States from theUSACE Waterways Experimental Station (1953) gives a summaryof this testing, which includes the standard tests for sulfate sound-ness, abrasion resistance, specific gravity, and absorption. Thiscompilation, which occupies nearly a meter of shelf space, cannotbe purchased but is available for inspection at USACE libraries.Other, more accessible publications that give physical test valuesand results of USACE extensive research relating to the use of car-bonate rock as aggregates in portland cement concrete include oneby Curry and Buck (1966). The most current list of USACE publi-cations is available from the Engineer Research and DevelopmentCenter Professional Library Services, an online library at http://www.edrc.usace.army. mil/library/publications.

Some manufacturers of pulverized limestone, defined as lime-stone or dolomite having a minimum fineness of 97% passing a325-mesh sieve, established standards and test methods through thePulverized Minerals Division of NSSGA. Recommended test meth-586 Industrial Min

The American Society for Testing and Materials (ASTM)Directory of Testing Laboratories, Commercial-Institutional (2005)lists laboratories capable of making chemical and physical determi-nations on rocks.

Physical PropertiesProcedures for physical testing can be obtained from two main

Table 5. Physical properties of selected carbonate rocks

Age Formation Location Rock Type

A

Miocene Unspecified Eniwetok Limestone (fossiliferous)

Eocene Unspecified Eniwetok Limestone (dense)

Cretaceous Niobrara S. Dakota Limestone (chalky)

Mississippian St. Louis Missouri Limestone (oolitic, fossiliferous)

Mississippian Maxville Ohio Limestone (fine-grained)

Mississippian Salem (Spergen) Indiana Limestone (fossiliferous)

Devonian Columbus Ohio Limestone (very fine-grained)

Devonian Columbus Ohio Limestone (fine-grained)

Silurian Brassfield Ohio Limestone (dolomitic)

Silurian Niagara Ohio Dolomite (fine-grained)

Silurian Clinton Alabama Limestone (coarse-grained)

Ordovician Chickamauga Tennessee Limestone

Ordovician Lenoir W. Virginia Limestone (siliceous)

Ordovician Knox Tennessee Dolomite (fine-grained)

Cambrian Bonne Terre Missouri Limestone (dolomitic)

Cambrian Oro Grande California Marble

Precambrian Cockeysville Maryland MarbleUnfortunately, most data from testing of aggregate in the federalhighway program have not been tabulated. Marek (1991) gives aals and Rocks

useful overview of sampling and testing principles. Unfortunately,much of that material is dated relative to changing highway con-struction methods and materials requirements. The InternationalCenter for Aggregates Research (ICAR) is now the focal point ofcurrent aggregate research. ICAR is a collaborative effort of theUniversity of Texas at Austin and Texas A&M University and hasvery strong ties to the National Stone, Sand, and Gravel Associa-

arent ecificavity

Apparent Porosity,

%

Compressive Strength,

MPa

Modulusof Impact,

MPaToughness,

cm/cm2 Reference

.39 4.0 97.2 16.5 0.4 Blair (1956)

.53 122.0 22.0 0.8 Blair (1956)

.81 8.3 25.5 4.1 0.5 Blair (1955)

.56 115.8 15.9 1.1 Blair (1956)

.41 108.9 17.2 1.2 Blair (1956)

.37 11.0 75.2 11.0 0.7 Windes (1949)

.60 5.4 123.4 1.4 Blair (1956)

.69 0.7 196.5 20.0 3.4 Windes (1949)

.8 1.3 179.2 193.1 1.6 Windes (1950)

.4 8.6 89.6 75.8 0.7 Windes (1950)

.83 0.9 165.5 2.6 Windes (1949)

.73 3.4 >173.0 5.5 2.2 Blair (1956)

.68 6.0 158.6 13.1 1.0 Windes (1950)

.84 0.7 322.0 26.2 2.3 Windes (1949)

.66 3.3 175.1 12.4 1.9 Blair (1955)

.72 0.2 165.5 16.5 0.7 Blair (1955)

.87 0.6 212.4 19.3 1.1 Windes (1949)ods include those for particle size, pH, dry brightness, waterdemand, and calcium and magnesium carbonate content.

nLimestone a

Petrographic examination of carbonate rock can foretell itsphysical properties and subsequent suitability for certain uses, buttoo few people use this method. The definitive reference for thistype of applied petrography is ASTM Standard C295, which isbased on work from the 1950s. Techniques of petrographic exami-nation and some of its applications can be found in Mielenz (1954,1955), and Scholle (1978).

Rippability is a physical property of rock that concerns mainlythe construction industry. Limestones that are thinly bedded, low incompressive strength, or sufficiently inhomogeneous so as to con-tain horizontal planes of weakness can generally be ripped easily.Empirical testing by the Caterpillar Tractor Co. (1972) found a rela-tionship between seismic wave velocities and rock rippability: thehigher the wave velocity, the more difficult it is to rip the rock.

Various research workers have examined the relationshipsbetween different physical and chemical properties of carbonaterocks. These attempts have not met with much success because ofthe inhomogeneity of the rocks. Further information can be foundin Judd and Huber (1961), West and Johnson (1965), Baxter andHarvey (1969), and Barksdale (1991).Chemical PropertiesThe chemical and physical properties of carbonate rocks are inter-dependent. Pure calcite in the form of poorly cemented chalk is notonly unique in its low strength and high absorption among the car-bonate rocks but is also highly reactive chemically because of thelarge surface area of its component grains. Pure calcitic marble ofthe same chemical composition as chalk is relatively strong, unab-sorptive, and unreactive. Dolomite that contains quartz sand grainscan have the same overall composition as dolomite that containschert, but its suitability as aggregate differs widely because of thedifference in reactivity of the two forms of silica. Processing alsoaffects the degree of fracturing of stone and thus its surface areaand chemical reactivity. Therefore, physical and mineralogicdescriptions of carbonate rocks are of importance in predicting thechemical properties of the products that may be produced from adeposit.

For some uses of carbonate rocks, chemical analysis may beof little or no help in estimating the suitability of a rock unit; forother uses chemistry is of utmost importance. For example, in stoneused for chemical purposes, such as glass raw material, flux, orcement, the percentage of certain elements must fall within speci-fied limits or ranges. On the other hand, the chemical content mayor may not be important for stone that is used because of its physi-cal properties, such as aggregate, building stone, or riprap. A thicksection of rock that is almost pure dolomite is likely to be well-cemented reefal dolomite, and it can be predicted generally to makegood aggregate (Ault 1989). Rock that is pure calcite, however,may be a skeletal or oolitic limestone that is either well cemented orpoorly cemented and thus might make excellent or only fair aggre-gate.

The proportion of alumina (A12O3) and silica (SiO2) in therock may be helpful in determining the value of a carbonate rockfor a use in which physical properties are important. Most silica in acarbonate rock is likely clay, silt- and sand-size quartz, or chert. Forthe common clay minerals found in limestones and dolomites, asmuch as 2% silica may be present for each 1% of alumina. Thehigher the alumina content, the more argillaceous the sample islikely to be. The alumina content can be multiplied by two to obtainan estimate of the amount of silica tied up in the clay.

The chemical analysis of a carbonate rock is essential for esti-

mating the neutralizing value of agricultural limestone, which isusually expressed in terms of calcium carbonate equivalent (CCE).d Dolomite 587

Pure calcite (CaCO3) is assigned a CCE value of 100. Pure dolo-mite (CaCO3MgCO3) has a theoretical CCE value of 108.6; that is,it is 8.6% more effective than pure limestone as a neutralizer. Suchinterpretation assumes that a molecule of MgCO3 with a molecularweight of 84.32 is as effective a neutralizer as one molecule ofCaCO3 with a molecular weight of 100.09. Thus, a given weight ofMgCO3 is 1.19 times as effective as the same weight of CaCO3.Because of differences in solubility, however, a dolomitic limingmaterial will take longer to neutralize a given amount of acid than apure limestone, even though the CCE of both is the same. Goodwin(1979) is a useful guide to selecting agricultural limestone materi-als, as is information available from several state agency Web sites(see Additional Resources section in this chapter).

Many published chemical analyses of carbonate rocks showthe varied compositions of limestones and dolomites (Clarke 1924;Graf 1960b; Siegel 1967), but these may not always be typical ofthe formation from which they were taken. Most sedimentary car-bonate rocks vary in their impuritiesincluding clay minerals,resistant minerals such as quartz, and organic materialbecausethey were deposited in different environments. In addition, therocks have evolved chemically as well as physically during com-paction, dehydration, and lithification. Subsequent processes,including burial and exposure to percolation of water, provide forsynthesis of authigenic minerals and alteration, such as oxidation oforganic matter. Because of the limited extent of identical environ-ments of deposition and subsequent postdepositional conditions,composition of any given rock unit is likely to be variable. Analysesof many samples taken at different sites are required to reveal theapproximate composition of a particular rock unit.

Good sources of chemical data on carbonate rocks are thestate geological surveys or their equivalents. Many state surveyshave files of chemical data obtained from quarry sampling and cor-ing programs. The USGS has published 1,131 analyses of carbon-ate rocks from Colorado, Kansas, Montana, Nebraska, NorthDakota, South Dakota, and Wyoming (Hill, Werner, and Horton1967) and 3,585 analyses of carbonate rocks from Alaska, Idaho,Oregon, and Washington (Hill and Werner 1972).SpecificationsLimestone specifications vary with end use of the stone. These spec-ifications can be either physical or chemical, but frequently theyinclude both. Physical specifications such as durability and grada-tion are more important if the stone is to be used as mined, such asfor construction aggregate. Chemical properties are more importantif the stone is to be subject to calcination, as in the production oflime or cement. Most industrial and agricultural applications requireadherence to both a physical and a chemical specification. Forexample, glass-batch raw materials might have both a rigid chemicalspecification and a narrow gradation requirement.

Physical specifications focus on both the natural properties ofthe rock and the properties imparted during processing. Naturalproperties are intrinsic, such as hardness, composition, texture,color, porosity, and density, and processing properties are derivedfrom the physical gradations and result from crushing, screening,washing, and air classification. Obviously the results of processingare directly related to the natural characteristics of the stone.

Physical specifications relating to gradation and durability areby far the most common when the rock is used as aggregatematerial. These specifications are based on standardized testing andpractices developed through ASTM. ASTM-specified gradingrequirements for coarse aggregate are shown in Table 6. Other

related ASTM physical specifications can be found in ASTM 2004(Section 4Construction).

rnASTM standards provide guidelines for both required grada-tions and test methods employed in evaluating materials for use asconstruction aggregates. The specific gradation requirements mayvary to some degree by individual state as a result of specificregional application or generally accepted practices. As an exam-ple, Table 7 compares gradations for an ASTM No. 8 specificationwith gradation for a No. 8 stone from Ohio, Indiana, and Kentucky.

Although there may be state-to-state modifications or varia-tions in physical gradations of specific stone sizes, most states gen-erally have durability requirements that are fairly consistent acrossthe United States for aggregates for use as highway surface materi-als. The most common specifications for durability relate to abra-

ability to withstand repeated cycles of weathering and continuedimpact of traffic. Several states have also included skid resistancefor aggregates to be used in surface-course paving and bridgedecks. As a consequence, several states have excluded carbonaterocks for these uses because they polish easily.

Frequently, the specifications for rock used in projects notfunded by states or the federal government are modified for eco-nomic reasons such as lower transportation costs. This type ofproject could include nonsensitive uses such as subgrade materialfor driveway or other nonload-bearing purposes. Conversely, ahigher transportation cost might be justified to achieve a specificappearance, as in some exposed-aggregate applications where

357 11/23/4 in.(37.519.0 mm)

95100

4 11/2 in.No. 4(37.54.75 mm)

100 90100 2055 015 05

467 11/2 in.(37.54.75 mm)

100 95100 3570 1030 05

5 11/2 in.(25.0 to 12.5 mm)

100 90100 2055 010 05

56 13/8 in.(25.09.5 mm)

100 90100 4085 1040 015 05

57 1 in.No. 4(25.04.75 mm)

100 95100 2560 010 05

6 3/43/8 in.(19.09.5 mm)

100 90100 2055 015 05

67 3/4 in.No. 4(19.04.75 mm)

100 up to 100 2055 010 05

7 1/2 in.No. 4(12.54.75 mm)

100 90100 4070 015 05

8 3/8 in.No. 8(9.52.36 mm

100 85100 1030 010 05

Source: ASTM 2004.

Table 7. Comparison of size gradations no. 8 stone screen size % passing

State Specifications 1 in. 1/4 in. 1/2 in. 3/8 in. No. 4 No. 8 No. 10 No. 16

ASTM NA* 100 85100 1030 010 NA 05

Ohio NA NA* 100 85100 1030 010 NA 05

Indiana 100 85100 2060 NA 05 02 NA NA

Kentucky NA 100 8595 4065 520 05 NA NA* NA = not applicable.588 Industrial Mine

Table 6. Grading requirements for coarse aggregates

SizeNumber

Normal Size Range(Sieves with

Square Openings)

Amounts Finer tha

4 in

.(1

00 m

m)

31/2

in.

(90

mm

)

3 in

.(7

5 m

m)

21/2

in.

(90

mm

)

2 in

.(5

0 m

m)

1 31/211/2 in.(9037.5 mm)

100 90100 2560

2 21/211/2 in.(6337.5mm)

100 90100 3570

3 21 in.(5025.0 mm)

90100sion, soundness, and freeze-thaw, all of which are covered by anASTM standard procedure. These tests are a measure of the rocksals and Rocks

Each Laboratory Sieve (Square-Openings), wt %

11/2

in.

(37.

5 m

m)

1 in

.(2

5 m

m)

3 /4

in.

(19

mm

)

1 /2

in.

(12.

5 m

m)

3 /8

in.

(9.5

mm

)

No.

4(4

.75

mm

)

No.

8(2

.36

mm

)

No.

16(1

.18

mm

)

015 05

015 015 05 05

3570 3575 1030 05architectural requirements are more important than economicconsiderations.

nLimestone a

Chemical specifications for carbonate rocks generally areindustry or application specific. In any consideration of chemicalspecifications of a limestone or dolomite, it is important to under-stand that chemical properties are not necessarily related to physicalproperties. For example, high-purity limestone from the MosheimFormation in Virginia is very hard, whereas equally pure limestonefrom the Ocala Formation in Florida is very soft. The marble fromthe Franklin Formation in New Jersey has both high-brightness andhigh-carbonate values, yet the dark gray, almost black, marble fromMichigans Dundee Formation has a higher calcium-carbonate value.

Limestone and dolomite specifications can be developed in avariety of ways, including rigid testing and evaluation, mutual con-sent between the buyer and seller, common practice in an area, oreven as a compromise to offset some other item such as high freightcost. A specification may also be written to describe a particularlimestone source, such as when the buyer is not sure which compo-nents are important for a particular application. In these instancesof uncertainty, the final specification results from testing severaldifferent limestones; selection is based on best performance.

Some specifications may be unique to a particular industryand require testing properties based on an industry standard orprocedure. Thermal decrepitation, odor, taste, and crystallinity areexamples of such properties. In some instances, these require-ments may be related to a specific company and be unique to thespecific application. For instance, when a limestone is used in ricepolishing, it may be subjected to a taste test to ensure that thelimestone does not impart an unpleasant taste to the rice duringpolishing.

As noted previously, it is not at all uncommon for a limestonespecification to incorporate both physical and chemical require-ments. This is particularly true of industrial uses such as glass man-ufacturing, where limestone is one component of the glass-batchraw materials. In this example, particle size, gradation, chemicaldegradation, and chemistry are equally important. Additionally,batch-to-batch uniformity of composition, both in chemistry andphysical properties, is important and may require statistical processcontrol (SPC). The importance of SPC should not be underesti-mated. For example, Tier One automotive glass producers requireall glass-batch suppliers of raw materials to employ audited SPC intheir process technology to qualify as an acceptable vendor. Severalmanufacturers also require ISO 9000 certification, although this isnot consistently applied to the limestone and dolomite industry.

Table 8 shows typical specifications for limestone to be usedin glass-batch raw materials. Industry-specific specifications suchas those required for limestone or dolomite used in the productionof lime or cement, in flue-gas desulfurization, and filler andextender specifications are included in the chapters on these materi-als. Any industrial or agricultural application, however, can have aunique specification predicated on specific performance require-ments. Individual publications on specifications and uses are avail-able at http://www.nssga.org.

PRODUCTION AND USESThe USGS reports that 1,130 t of limestone, dolomite, and relatedmaterials were sold or used in the United States in 2001 (Table 9) forconstruction purposes, including the production of lime and cement.As in previous years, carbonate rock was produced in 48 of the 50states, with only Delaware and North Dakota not reporting any lime-stone or dolomite production. The top five producing states indescending order were Texas, Florida, Missouri, Illinois, and Ohio.These five states accounted for 40.8% of total U.S. production.The tonnage is consumed in hundreds of applications, but thepredominate markets for limestone and dolomite can be dividedd Dolomite 589

into 9 major categories and 39 primary uses (Table 10). The firstfive major categories are related to the use of carbonate rocks asconstruction materials. A total of 430,613,000 t, or 38% of allcrushed carbonate rock produced in the United States in 2001 wasproduced for aggregate markets. Limestone and dolomite thus rep-resent 54% of the total 790 t of aggregate material sold or used.Agricultural applications consumed 11.7 t of limestone and dolo-mite, of which agricultural liming materials made up 83% of thiscategory. Chemical and metallurgical uses account for about 99.3 t,or about 8.8% of all the limestone and dolomite produced eachyear. Tegethoff (2001) gives additional information on the use andapplications of limestone.

Special uses cover a host of applications, the largest of whichare fillers, extenders, and whiting materials. Because of the uniqueapplications and value of these products, they are covered in a sepa-rate chapter. Mine dusting and acid water treatment are a uniquecategory unto themselves. High-calcium limestone (more than 95%

Table 8. Physical and chemical specifications for glass-grade limestone

Typical Physical Analysis

Size, mm % RetainedCumulative %

RetainedCumulative %

Passing

1.68 (12 mesh) 0.00 0.00 100.00

1.19 (16 mesh) 0.35 0.17 99.83

0.84 (20 mesh) 5.06 5.20 94.80

0.30 (50 mesh) 57.05 62.25 37.75

0.15 (100 mesh) 26.26 88.90 11.10

0.07 (200 mesh) 9.98 98.40 1.60

pan 1.60 100.00 0.00

Moisture content 0.09%

Typical Chemical Analysis

Chemical Reported as %

Calcium carbonate CaCO3 97.80

Magnesium carbonate MgCO3 1.25

Iron oxide Fe2O3 0.095

Silica SiO2 0.56

Alumina Al2O3 0.23

Nickel Ni

590 Industrial Minerals and Rocks

Table 10. Crushed limestone and dolomite sold or used by producers in the United States in 2002, by use*

Limestone Use Dolomite Use

Quantity, kt Value, $1,000 Quantity, kt Value, $1,000

Construction

Coarse aggregate (+37.5 mm) (+ 1/2 in.)Macadam 2,350 14,700 140 1,040Riprap and jetty stone 9,880 59,500 296 2,720Filter stone 3,120 18,900 73 522Other coarse aggregate 11,300 78,900 667 3,870

Coarse aggregate, gradedConcrete aggregate, coarse 34,600 229,000 3,400 20,700Bituminous aggregate, coarse 26,200 180,000 3,960 23,800Bituminous surface-treatment aggregate 5,800 41,900 1,090 5,610Railroad ballast 1,690 8,880 544 3,680Other graded coarse aggregate 65,700 423,000 1,930 15,800

Fine aggregate (3/8 in.)Stone sand, concrete 6,740 42,600 415 2,110Stone sand, bituminous mix or seal 3,890 23,900 868 5,800Screening, undesignated 10,900 57,900 639 3,270Other fine aggregate 22,500 150,000 954 6,910

Coarse and fine aggregatesGraded road base or sub-base 64,600 326,000 5,700 27,600Unpaved road surfacing 10,600 60,300 807 4,090Terrazzo and exposed aggregate 168 1,280 0 0Crusher run or fill or waste 17,400 84,500 1,150 7,240Roofing granules 214 1,720 0 0Other coarse and fine aggregates 49,200 275,000 8,500 43,400

Other construction materials 5,880 37,900 488 2,700Agricultural

Agricultural limestone 9,660 57,300 848 5,560Poultry grit and mineral food 932 9,980 0 0Other agricultural uses 271 2,980 67 316

Chemical and metallurgical

Cement manufacture 67,100 299,000 95 341Lime manufacture 18,700 99,600 1,480 6,160Dead-burned dolomite manufacture W W W WFlux stone 1,440 7,940 811 3,630Chemical stone 313 2,700Glass manufacture W WSulfur oxide removal 2,990 20,100

Special

Mine dusting or acid water treatment 168 1,850Asphalt fillers or extenders 730 5,430 W WWhiting or whiting substitute 126 1,830 W WOther fillers or extenders 1,550 21,200 15 171

Other miscellaneous uses

Refractory stone 1,070 4,730Sugar refining W WOther specified uses not listed 6,930 34,800 123 639

Unspecified**

Reported 306,000 1,550,000 49,300 282,000Estimated 210,000 1,000,000 13,000 69,000

Total 978,000 5,230,000 97,400 549,000

Source: Tepordei 2002.* Data are rounded to no more than three significant digits; may not add to totals shown. Includes a minor amount of limestone-dolomite reported without a distinction between the two. Includes building products, drain fields, and pipe bedding.

Withheld to avoid disclosing company proprietary data; included in Total.

** Reported and estimated production without a breakdown by end use.

nLimestone a

is normally ground to 95% less than 325 mesh. Limestone or dolo-mite used in acid-water treatment can be specified with a variety ofsizes depending on both the pH of the water to be treated and avail-able residence time. In some instances, limestone may be injectedas a 325-mesh powder into a low-pH effluent stream, or it might beused as boulders in acid streams not suitable for continuous treat-ment with finer-grained materials.

Dimension stone is the one category not included in Table 9.Dimension stone production is closely tied to commercial construc-tion; in 2002 about 1.26 Mt were produced in the United States.Limestone and marble together account for approximately 33% oftotal U.S. dimension-stone production. Indiana was the leadingstate in dimension limestone production, and Georgia was the lead-ing state for dimension marble production, followed by Vermont.

When granite production is included with limestone and mar-ble production, the United States is the fourth largest producer ofdimension stone in the world. Nevertheless, total U.S. dimension-stone production has historically been one fourth that of Italy andone half that of Spain (Harries-Rees 1991). Italy, Spain, and Greeceproduce more dimension stone than the United States; each is a netexporter and the United States is a net importer of dimension stone.

Interestingly, dimension stone production is reported in tons,but sales and prices are normally based on the cost per cubic foot.These prices have remained fairly constant over the last severalyears; increases in profitability realized by producers have comefrom increases in productivity.

PREPARATION FOR MARKETMiningLimestone and dolomite are high-volume, low-value commodities.This segment of the industrial minerals industry is highly competi-tive and is characterized by thousands of operations serving localand regional markets. Thus a competitive environment dictates thatproduction cost control is the critical element in any stone operation.

Most limestone and dolomite are mined from open quarries,although in many areas economic and environmental considerationsfavor large-scale production by underground mining. The only car-bonate materials not consistently recovered by surface or under-ground mining are shell products that are dredged from parts ofU.S. coastal waterways, and this is coming to an end with increasedenvironmental pressure in conventional areas of shell production.

Surface MiningThe basic elements of surface mining are overburden removal (strip-ping), drilling, blasting, and hauling ore to the crushing and process-ing plant. Ultimately the surface mine must also contend withreclamation requirements. The selection of surface mining equip-ment varies with the particular requirements at each operation,including production capacity required, size and shape of thedeposit, haul distances, estimated life of the operation, location rela-tive to urban centers, and other social and economic factors. Otherfactors that must be considered in surface mining are the value of theproducts produced, location of competitive operations, and environ-mental and safety requirements associated with a particular deposit.

Frequently, a surface mine or quarry will contract for the drill-ing or blasting part of the production cycle. The specialized natureof this aspect of production, combined with the unique regulatoryand safety requirements associated with the handling and use ofexplosives, may make the use of an outside contractor economi-cally attractive, particularly for quarries close to densely populatedurban environments. The contractor is responsible for the mainte-

nance of an explosives magazine and all record and reportingrequirements and may arrange for seismic monitoring of each blast.d Dolomite 591

The issue of explosives handling and storage has become muchmore highly regulated since September 11, 2001, adding consider-able incentive to using an outside contractor.

Overburden removal is a key element in the cost of any surfacemining operation and consequently its ability to compete with othermines in its market area. For example, if 3 m of overburden must beremoved to recover 30 m of limestone, a mine with 15 m of overbur-den for the same 30 m of rock will not be competitive. If a mine isunique to its particular area, however, a high overburden ratio maybe economically justified. Additionally, the production of high-valueend products may support mining operations that would not beeconomical for low-value products. For example, in East Tennessee,as much as 90 m of overburden has been removed from a 30-m-thick, steeply dipping deposit of chemical-grade limestone for use inthe production of lime. This high overburden ratio would probablynot be justified if this were a conventional aggregate operation.Underground MiningIn 2002, 83 underground limestone mines were operating in theUnited States. In 1900, total production of limestone from all under-ground mines was 95 kt, or 0.37% of the total limestone production.In 1924, production was 520 kt, or 4.5% of the total production. In1965, it was 31,200 kt or about 6% of the total limestone production.In 2002, it was 60,000 kt or about 5.3% of the total production.Many of the mines are in the Midwest, however, and this reflects theabundance of high-quality limestone in horizontal beds in that partof the country as much as a concentration of population. This distri-bution pattern will change gradually as more mines are built to serveurban centers (Carr and Ault 1983; Baxter 1989).

The basic operations in underground mining are drilling,blasting, loading and hauling, scaling, and roof bolting. Drillingequipment includes horizontal drill jumbos and downhole trackdrills. This equipment is generally quite different from that used forsurface mining and results in much smaller blast holes and a lowervolume of rock pulled with each blast. Other equipment required inthe underground mine includes powder loaders, which are used toblow ammonium nitratefuel oil mixtures into the blast holes. Scal-ing rigs, which are used to remove loose rocks from the ribs androof of the mine, and roof-bolting equipment may also be requiredin an underground mine.

Most underground limestone and dolomite mines are room-and-pillar-type operations, and many recover rock from both head-ings and benches. It is not uncommon for an underground limestonemine to have several benches and an overall mine height up to 30 m.Whereas the thickness of the deposit being mined is directly con-trolled by the thickness of the rock and related roof conditions, it isnot uncommon for an individual heading to be 7.5 to 10.5 m high,and in some instances to reach as high as 15 m. Rooms are generally13.5 to 15 m wide, which, depending on the type of drilling jumboused, normally can be mined with one- or two-drill setups. A V-typedrill pattern is commonly used to maximize the amount of rockpulled with each shot to reduce the number of boots or unbrokenrock in the shot face. Scaling is normally required as a safety mea-sure; roof bolting may or may not be required, depending on roofconditions at the individual mine. Loading and hauling equipmentmay include standard 22 to 45 Mt haul trucks and correspondinglysized front-end loaders. In some mines, the loading equipment maybe more typical of underground hard-rock operations, and mayinclude load-haul-dump units or other types of tramming equipment.For more detailed information on both surface and undergroundmines, the reader is referred to Kennedy (1990), Bise (1986), and

Hartman (1992).

ra592 Industrial Mine

ProcessingLimestone processing varies with the end product and targeted con-suming industry but of necessity includes several basic similarities.These similarities relate primarily to sizing and include crushing andscreening. Depending on such factors as the volume of rock pro-cessed, type of mine, haulage distance, and surface topography, pri-mary crushing may be done either at or near the mining face or at theprimary processing plant. When primary crushing is done in thequarry or mine, the rock is normally reduced to a less than 15-cmdiameter and is moved via conveyor to the main processing plant.

Selection of crushing equipment depends on plant size, physi-cal properties of the rock, and the product produced. In general, pri-mary crushing is by a jaw or gyratory crusher, but an impactcrusher or other specialized equipment may be used. Several under-ground limestone mines use Stamler feeder-breakers as the primarycrusher, which is a low-profile piece of equipment. Secondarycrushing is usually by cone or gyratory crushers, although impactand roll crushers and hammer mills may be used.

Screening is one of the most critical steps in the processingcycle, particularly in the production of crushed stone. The selectionfrom a wide variety of screen types and screen cloth depends on therequirements for the end product. Most screens incorporate someform of inclined vibratory equipment. Screen cloth can range froma rod, a deck, or punctured steel plates for larger product sizesdown through woven wire, welded wire cloth, rubber, plastic, andpolyurethane for smaller product sizes. Screens must be checkedregularly for holes and tears because oversized material can quicklycontaminate a significant volume of product. Stainless steel is fre-quently used for the screen cloth to reduce wear and increase screenlife.

Quarried stone usually has some moisture associated with it,and, as a consequence, fines may adhere to larger pieces of rock.Many crushed stone facilities include washing equipment in theproduction line to remove these fines and thus ensure gradationspecifications and the removal of clay or soft shale. Where washingfacilities are included in the processing cycle, settling ponds arealso required to eliminate the discharge of silt-laden water to neigh-boring streams. Where stone washing is not practical and whenmoisture cannot be tolerated in either subsequent processing stepsor the final product, a dryer may be required. The dryer is normallyinstalled ahead of the screening equipment. These dryers are usu-ally counterflow rotary dryers that operate at 120C to 150C. Flu-idized-bed dryers may also be used and are particularly applicablewhere flash calcination of fines might be a problem.

Limestone and dolomite processing for industrial and agricul-tural applications may also require air classification and millingequipment, particularly when products are smaller than 10 mesh andmust have a clean bottom cut (usually at 100 or 200 mesh). Air clas-sifiers are easily adjusted and have the flexibility to make a widerange of products. Cage mills, roller mills, and ball mills are usedin the production of varying particle sizes ranging from 20 mesh to2 m. Wet processing is usually required to produce productssmaller than 2 m.

Once processed, the stone products must be stored beforeshipment. Most crushed stone products are stored in open areas orin a combination of open areas and loading bins. The volume ofmaterial produced and the variety of products generally dictate thedesign of the storage area. In many larger aggregate operations, aseries of radial stackers distribute stone from the screening plant.Alternatively, a plant may have several stone bins to facilitate truckor rail loadout. Storage of industrial and agricultural products

requires enclosed silos and bins to protect them from moisture andcontamination by other products. These bins and associated loadoutls and Rocks

devices require positive dust control, including adequately sizedbaghouses. They may also include pneumatic conveying equipmentor bucket elevators in the product-handling system.

Programmable controllers or computers are finding increaseduse in the processing of limestone and dolomite. As process plantsbecome larger and more complex, computer-controlled processingsystems are an invaluable tool in achieving improved productionefficiencies and improved product quality. This equipment can beincorporated into the statistical process-control program of theplant and can be interactive with loadout and scale computers.Where interactive systems are used, they can provide on-line inven-tory control, bills of lading, and input directly from loadout scalesto computer-generated invoicing. Several software packages avail-able today are particularly well adapted to aggregate operations. Auseful reference is the NSSGA publication Guidelines for the Suc-cessful Automation in the Crushed Stone Industry, which can besupplemented with the proceedings from the NSSGA annual Auto-mation Conference (NSSGA 1990). The annual proceedings can bepurchased through the NSSGA Web site (http://www.nssga.org).TransportationTransportation is a major factor in the delivered price of limestoneand dolomite products. In very general terms, the lower the value ofthe processed product, the shorter the distance it can be transported.Stated another way, construction aggregates are less likely to movelong distances to the marketplace than are 2-m carbonate filler/extender materials. In many places, the cost of transportation equalsor exceeds the free on board (f.o.b.) plant value of the stone. Thus,limestone and dolomite aggregates generally are marketed locally.

In the limestone and dolomite chapter in the 6th edition ofIndustrial Minerals and Rocks, it was reported that truckingaccounted for 82% of the transportation of limestone and dolomiteproducts in the United States. The remainder of the material wastransported about equally by rail or waterway. This distribution hasnot changed appreciably in the last 10 years; however, many factorsrelated to the cost of transportation have changed. Both rail andtrucking rates have been deregulated, and competition functionsopenly in the marketplace. As a consequence, it is frequently possi-ble for a stone processing company to negotiate rates for specificjobs or contracts. This competition also has fostered a number ofunit train and intermodal transportation arrangements that haveallowed aggregate products to be delivered to more remote loca-tions than previously thought possible.

In evaluating the cost of trucking limestone and dolomiteproducts, the trucking costs associated with aggregate and crushedstone materials must be considered separately from the cost oftransporting higher value industrial and agricultural products. Thespecifics of trucking vary from area to area; however, in very gen-eral terms, approximately half the trucking of crushed stone is doneby a contractor purchasing and using the aggregate as opposed toowner/operators or commercial haulers. Many state and local gov-ernments also have their own trucking equipment and can begrouped with those contractors hauling for their own purposes orjobs. For them, the actual cost of trucking is extremely difficult todetermine because each values and costs transportation somewhatdifferently. For owner/operators or contract haulers using opendump trucks for hauls of less than 40 km, a charge of $0.06 to $0.10per metric ton-km is not uncommon. These rates are subject tonegotiation and may be cut significantly on very large constructionprojects; they also do not include fuel surcharges.

In many places, trucking of industrial and agricultural prod-

ucts is handled differently from the hauling of limestone and dolo-mite aggregates. The equipment normally used includes pneumatic

nLimestone a

tankers, bottom-dump grain trucks, and vans and flatbeds forbagged products. Where bottom-dump grain haulers can be used,back-haul freight rates may be possible, thus allowing the producerto reach customers whose geographical location is far more remotethan would otherwise be economical with normal tariff rates. Con-tamination by foreign matter is a major concern for many indus-trial customers; consequently, some carbonate producers operatetheir own equipment or contract with a specific hauler for dedi-cated equipment. Even then, it may be necessary to use rigorousclean-out procedures to prevent contamination, particularly whenbulk micrometer-sized product is being trucked. Because of thespecialized nature of equipment used for industrial and agriculturalpurposes, trucking rates tend to be slightly higher than those foraggregate products and may be in the $0.10 to $0.20/t-km range.These rates may also be subject to negotiation when a consistenthaul can be established and several units can be dedicated to aspecific customer.

Railroads continue to be a major factor in the transportation oflimestone and dolomite products, whether aggregate materials orindustrial and agricultural products. For aggregates, rail movementmay use intermodal facilities at the receiving end where the stone iseither transferred to a stockpile or directly to a truck for delivery tothe customer. Such facilities are used successfully in selected mar-kets and most recently were employed by one Pennsylvania pro-ducer to move aggregates into the Baltimore-Washington marketarea. On a single line haul with 60 to 90 car unit trains, it is possibleto ship aggregate products at a cost of $0.02 to $0.06/t-km. In manyplaces, agricultural and industrial customers are large-volume usersand require the use of covered-hopper equipment. In these instancesit is possible to negotiate very favorable rail freight rates if a single-line haul can be used. The negotiation of favorable rail rates, how-ever, becomes far more difficult when two or more rail lines areinvolved and when short-line rail carriers impose switchingcharges. Nevertheless, even in multiline hauls, when the competi-tion is a straight truck movement, the volumes of stone to be trans-ported may justify a very competitive bid from the combined raileffort. The downside to rail utilization is that the railroads havebecome quite aggressive in assessing service fees, including demur-rage, switching fees, and surcharges, which can greatly increase thecost of rail freight.

Waterway transportation continues to handle about the samevolume of stone products that it has for the past 10 years. Most of thestone moved via waterway is either construction aggregate or chemi-cal-grade limestone or dolomite used in the production of lime orcement. Transportation by barge normally requires a shipment of1.4 kt per barge and generally is not attempted on movements shorterthan 480 km. Freight quotations of $0.01/t-km are not uncommon.Barges are not the only means of waterway transportation. Self-unloading ore carriers on the Great Lakes, oceangoing barges, and27- to 54-kt bulk ship movements on the ocean are also being used tomove crushed stone. Ocean freight and Great Lakes shipment ratescan be very economical when this mode of transportation is feasible,but it is clearly restricted to large-volume movements.

LEGISLATIVE AND ENVIRONMENTAL ISSUESLimestone and dolomite producers, along with the rest of the min-ing industry, are faced with an ever-increasing array of regulatoryand environmental legislation. The average U.S. citizen today is farmore environmentally conscious than just 10 years ago. As a conse-quence, the public expects a positive and responsible commitment

from the mining industry to environmental, health, and safety con-cerns. These concerns separate into two basic groups: local com-munity sensitivities, and state and federal mandates.d Dolomite 593

At the local level, the limestone industry is faced with zoningand community relations requirements, the response to which willdictate the success or failure of each quarry or mine in the yearsahead. The response by stone producers must include long- andshort-range reclamation plans, aggressive dust and noise control,attention to the aesthetics of plant entrances and other street-appealitems, and a willingness to listen to community concerns. In someinstances, restrictions may be imposed on the hours that blastingcan take place or on the hours a quarry may operate. One of themajor concerns of many communities is the traffic associated withquarry or mine operations. In some places, trucks moving to andfrom a limestone producers operations must travel through neigh-boring residential areas. As a consequence, additional driver safetyand courtesy training may be required, and speed restrictions mustbe aggressively enforced.

State and federal regulations include a number of items ofcritical interest to the limestone and dolomite industry. As previ-ously noted, reclamation plans may be a critical part of the permitprocess and should be developed well in advance of mining. Inyears past, limestone producers could view reclamation require-ments as a future issue not needing current planning or engineer-ing. Today, many local communities, and some states, requirelong-range operating plans that include the reclamation of aban-doned areas concurrent with active mining or quarrying. Reclama-tion plans need to specifically address several items, includinglong-term land use decisions, health and safety of the community,and elimination of hazardous wastes and other potentially toxicdischarges.

State and federal legislation under debatesuch as theUSACE and U.S. Environmental Protection Agency (EPA) federalwetlands regulations found in Section 404 of the Clean Water Actand associated legislationwill likely have a significant impact onthe mining industry. Given the current federal guidelines of no netwetlands loss and the location of many limestone and dolomiteresources, conflict appears to be inevitable, although mitigationguidelines can be found at www.mitigationactionplan.gov. Indus-trial, environmental, and political factions are currently debatingthe definition of wetlands, and it may be some time before what isand what is not a regulated wetland can be clearly defined. Thisissue is being litigated in the federal court system, along with ques-tions of jurisdiction between federal and state agencies.

Other critical issues receiving public attention include respira-ble crystalline silica, storm-water runoff, underground fuel storagetanks, Phase II of the Clean Air Act Amendments of 1990, andpotential revisions to the Endangered Species Act. The crystalline-silica issue is of particular concern since silica has been declared acarcinogen by the National Institute for Occupational Safety andHealth, and tort claims are being filed even though the specifics forupdated Occupational Safety and Health Administration and MineSafety and Health Administration regulation have yet to beadopted. Several environmental groups and labor unions have chal-lenged current regulations on silica (30 CFR, part 71.01), sayingthat they are too low. This issue is being both debated and litigated.

Storm-water runoff is another environmental issue that thequarry operator must address. The EPA requires storm-water dis-charge permits for all mining operations, and requires that the per-mit applicant consider potential groundwater contaminationresulting from quarry or mining activities. The NSSGA is workingextensively with state and federal regulatory agencies and stoneproducers to assist in the development of and compliance withthese regulations. The NSSGA Web site maintains regular updates

on regulatory issues and governmental actions affecting the crushedstone industry (http://www.nssga.org).

rals and Rocks594 Industrial Mine

Federal mandates to eliminate underground fuel storage tankshave been in place for many years. These tanks could potentiallycontaminate groundwater as they age and develop leaks. Because itis extremely difficult to monitor the integrity of these undergroundtanks, their removal has been strongly encouraged. In addition, it isalso necessary to provide adequate containment structures aroundsurface tanks to mitigate potential environmental issues that couldresult from a spill.

FUTURE TRENDSLooking ahead to the next decade, the demand for limestone anddolomite is expected to grow at an average annual rate of about2.0% to 2.5%. Limestone is the primary raw material for crushedstone, and its demand is expected to match the demand for new con-struction. In recent years, particular attention has been focused onthe nations deteriorating infrastructure and the need for repair andreplacement. Although the specifics of federal funding initiativesmay change from year to year, the fact remains that the federal andstate governments annually allocate hundreds of billions of dollarsto infrastructur repair and replacement.

The demand for chemical-grade carbonate rock used inindustrial and agricultural applications is expected to equal, at aminimum, the growth of the U.S. population. In addition, Phase IIof the Clean Air Act Amendments of 1990 could greatly expandthe demand for both lime and limestone for utility stack-gas scrub-bing. Lime is a primary reagent material for both wet and dryscrubbing, and limestone is used in both wet scrubbing and fluid-ized-bed combustion. These uses are covered in more detail else-where in this volume.

Although the demand for limestone and dolomite is expectedto remain strong throughout the twenty-first century, the structureof the U.S. stone industry is changing. The most pronouncedchanges relate to consolidation within the industry and the increas-ing role played by foreign owners. In the 1990s and continuing intothe early years of the twenty-first century, foreign and domesticcompanies completed mergers, acquisitions, and joint ventures thathave resulted in a continuing change in the names on the front gatesof many limestone and dolomite operations. Data from the USGS(Tepordei 2002) lists the U.S. top 10 crushed stone producers asfollows

1. Vulcan Materials, Birmingham, Alabama2. Martin Marietta Aggregates, Raleigh, North Carolina3. Hanson Building MaterialsAmerica, Neptune, New Jersey4. Oldcastle, Inc., Washington, D.C.5. Lafarge North America, Inc., Herndon, Virginia6. CSR, Ltd., dba Rinker Materials Corp., West Palm Beach,

Florida7. Cemex, Inc., Houston, Texas8. Rogers Group, Nashville, Tennessee9. Florida Rock Industries, Inc., Jacksonville, Florida

10. APAC, Inc., Atlanta, GeorgiaA second trend having an increasing impact on U.S. limestone

production is the role of imported crushed stone materials. Offshorelimestone operations located in Canada, the Bahamas, and Mexicohave been able to take advantage of low-cost ocean freight to reachmarkets along the east, west, and Gulf coasts of the United States.Newfoundland Resources and Mining Company, Ltd., initiated itsfirst shipments of limestone to the United States in May 1990, froma $30 million plant specifically designed for exporting crushed stone

by ship along the eastern coast of the United States. Canada is onlyone of the countries exporting crushed limestone to domestic U.S.markets. Martin Mariettas quarry near Freeport, Bahamas, and Vul-can Materials Mexican imports from the Yucatan have had signifi-cant impact on aggregate markets in Florida and along the U.S. GulfCoast. Martin Mariettas Bahamian quarry ships more 1.4 Mt annu-ally, and Vulcan reports that their operations near Cancun have acapacity of more than 3.6 Mt per year. The efforts of Vulcan Materi-als, Martin Marietta, and Newfoundland Resources and MiningCompany have been directed at the importation of crushed stone foraggregate materials, but they are not the only operations bringinglimestone into the United States. On a much smaller scale, white,chemically pure, industrial-grade limestone has also been importedfrom the Caribbean and China for use in filler/extender materials.These products, however, have thus far represented only a fractionof 1% of total high-calcium filler/extender material produced andsold in the United States. Additionally, both aggregate and chemi-cal-grade limestone is exported from Vancouver Island, BritishColumbia, Canada, to Pacific coastal ports.

In summary, limestone and dolomite have been and continueto be one of the most important raw materials in the United States.Demand will increase, albeit at a modest rate, and new uses andapplications will be found. But limestone and dolomite will con-tinue to be commodities produced and sold in a highly competitivemarketplace. Competitive pressure will dictate that limestone anddolomite producers be attentive to cost control and apply improve-ments in technology to increase productivity. Producers will alsohave to adapt to a social and political climate that will demand nodeterioration in the environment, and thus costs for limestone anddolomite products will increase.

ADDITIONAL RESOURCESThe Web sites of the geological surveys for each U.S. state andCanadian province offer a wealth of information about limestoneand dolomite. The URLs are given in Table 11.

ACKNOWLEDGMENTSThis chapter draws heavily on the chapter in the 6th edition ofIndustrial Minerals and Rocks, written by D.D. Carr, L.F. Rooney,and R.C. Freas. The authors of this chapter updated the data andinformation and revised selected material while leaving much ofthe chapter as originally written. Because limestone and dolomiteare the basic raw materials of a large segment of the constructionindustry, the majority of material presented in the 6th editionremains current.

BIBLIOGRAPHYAASHTO (American Association of State Highway and Transpor-

tation Officials). 2004. Standard Specifications for Transporta-tion Materials and Methods of Sampling and Testing. 24thedition. Parts I and II. Washington, DC: AASHTO.

Adams, A.E., and W.S. MacKenzie. 1998. A Color Atlas of Car-bonate Sediments and Rocks under the Microscope. New York:John Wiley & Sons.

ASTM (American Society for Testing and Materials). 2004. AnnualBook of Standards. Section 4Construction. Volumes 04.01,04.02, 04.03, 04.07, 04.08, 04.09. West Conshohocken, PA:ASTM International.

. 2005. Directory of Testing Laboratories, Commercial-Institutional. Available from www.astm.org/labs.

Ault, C.H. 1989. Construction materials: Crushed stone. Pages 5764 in Concise Encyclopedia of Mineral Resources. Edited byD.D. Carr and N. Herz. Oxford: Pergamon Press.

nd Dolomite 595

Indiana http://igs.indiana.edu Washington http://www.dnr.wa.gov/geologyAult, C.H., and Haumesser, A.F. 1990. A Central Indiana model forpredicting jointing characteristics in underground limestonemines. Pages 18 in Proceedings of the 24th Forum on Geologyof Industrial Minerals. Columbia: South Carolina GeologicalSurvey.

Austin, G.S., G.K. Hoffman, J. Barker, J. Eidek, and N. Gilson.1996. Proceedings of the 31st Forum on the Geology of Indus-trial Minerals. Bulletin 154. Socorro: New Mexico GeologicalSurvey.

Azaroff, L.V., and M.J. Buerger. 1958. The Powder Method inX-Ray Crystallography. New York: McGraw-Hill.

Baars, D.L. 1963. Petrology of carbonate rocks. Pages 101129 inShelf Carbonates of the Paradox Basin. Durango, CO: FourCorners Geological Society.

Barksdale, R.D., editor. 1991. The Aggregate Handbook. Washing-ton, DC: National Stone, Sand, and Gravel Association.

Baxter, J.W. 1989. Possible underground mining of limestone anddolomite in Central Illinois. Pages 2133 in Proceedings of the23rd Forum on Geology of Industrial Minerals. Edited by R.E.

Baxter, J.W., and Harvey, R.D. 1969. Alumina content of carbonaterocks as an index to sodium sulfate soundness. Pages 510 inIndustrial Minerals Notes 39. Urbana-Champaign: Illinois StateGeological Survey.

Birch, F., et al. 1950. Handbook of physical constants. SpecialPaper 36. Boulder, CO: Geological Society of America.

Bise, C.J. 1986. Mining Engineering Analysis. Littleton, CO: SME.Bissell, H.J., and G.V. Chilingar. 1967. Classification of sedimen-

tary carbonate rocks. Pages 87168 in Developments in Sedi-mentology, Carbonate Rocks. Volume 9A. Edited by G.V.Chilingar, H.J. Bissell, and R.W. Fairbridge. New York:Elsevier.

Blair, B.E. 1955. Physical Properties of Mine Rock. Part III. Reportof Investigations 5130. Washington, DC: U.S. Bureau of Mines.

. 1956. Physical Properties of Mine Rock. Part IV. Report ofInvestigations 5244. Washington, DC: U.S. Bureau of Mines.

Bush, A.L. and T.S. Hages. 1995. Industrial Minerals of the Mid-continent: Proceedings of the Mid-continent: Proceedings of theSurvey. Lexington: Kentucky Geological Survey.

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