MineralsandMining

Whatareminerals?• Amineral isdefinedasanynaturallyoccurringcrystallineinorganic material.– Theinternalstructureofamineralisalsoimportant.– Itschemicalsandhowtheyarearrangedmakesadifference.

– Somearecomposedofoneelement (Gold)• Asingleitemoffoftheperiodictable

– Mostmineralarecompounds – theyconsistoftwoormoreelementsthatarecombinedinconstantproportions.

– Somearemixtures – Multiplecompoundswhereyoucanseethedifferentcompounds(layers,colors,orshapes)-Rocks

Element,Compound,orMixture

Copper – Cu

Element

Pyrite – FeS2 –Iron Sulfate

Compound

Granite - Minerals are mostly quartz and feldspar, with small amounts of mica (muscovite or biotite). Igneous RockMinerals

Minerals

• Thereareover2000kindsofminerals,Whichone’sareworthlookingat?

• Almostanyrockyoufindwillcontainoneormoreminerals.

• Someareveryrareandvaluable

MineralProperties

• Color• Crystalform• Hardness• Cleavage• Streak• Luster• Density• Solubility

• Physical• Physical• Physical• Physical• Physical• Physical• Chemical• Chemical

Density

• Density=Mass/volume• Thestructureishighlyorderedandconstantforthatmineral– Agrainofsalthasthesamestructureasaboulderofsalt.

GeneralClassificationofNonrenewableMineralResources

• TheU.S.GeologicalSurveyclassifiesmineralresourcesintofourmajorcategories:– Identified:knownlocation,quantity,andqualityorexistenceknownbasedondirectevidenceandmeasurements.

– Undiscovered:potentialsuppliesthatareassumedtoexist.

– Reserves:identifiedresourcesthatcanbeextractedprofitably.

– Other:undiscoveredoridentifiedresourcesnotclassifiedasreserves

GeneralClassificationofNonrenewableMineralResources

• Examplesare:– fossilfuels• coal,oil

– metallicminerals• copper,iron

– nonmetallicminerals• sand,gravel

Figure 15-7

ENVIRONMENTALEFFECTSOFUSINGMINERALRESOURCES

• Theextraction,processing,anduseofmineralresourceshasalargeenvironmentalimpact.

Figure 15-9

Minerals

• Inacyclethatspanstensonmillionsofyears,tectonicplatesshift,grind,andrecycle earthmineralsinmanyways.

• Oncemineralsareuplifted tothesurface,theyundergoweathering.

• Theseplateinteractionlocationshavethegreatestconcentrationofminerals.

Minerals– Thereare92naturallyoccurringelementsonearthbutonlyeightelementsmakeover98%ofthemineralsontheEarth'scrust.Theyare,indecreasingquantity,1oxygen 5calcium2silicon 6sodium3aluminum 7potassium4iron 8magnesium

– Thereareover2000mineralsonEarth,butonly100arecommonlyfound.30mineralsmakeupthemajorityoftherocksonEarth.Rocksaremadeoftwoormoreoftheseminerals.

Ore

• Ore isanymaterialthatcanbeminedforaprofit.Metalornonmetal.

• Periodic Table– Metals aretheleftsideoftheperiodictable.– Non-metals therightsideofthetable.

Ore

• Orebodies aredepositsoraccumulationsoforeinamassofrock.

• Non-renewable

• Thepricedeterminesthepotentialprofitvs.amountfound.

1. Prospecting: finding places where ores occur2. Mine exploration and development: learn whether ore can be extracted economically3. Mining: extract ore from ground4. Beneficiation: separate ore minerals from other mined

rock5. Smelting and refining: extract pure commodity from

the ore mineral6. Transporation: carry commodity to market7. Marketing and Sales: Find buyers and sell the

commodity

StepsinObtainingMineralCommodities

MiningandtheEnvironment

• Mininghasanimpactbecausemineralsareremovedfromtheearthbyundergroundor surfaceexcavations.

• Theimpactdependsontheland,thewater,thedepthofmineral,theamountremoved,methodused,soiltype,andsurroundingrock.

• Itcanalsoeffecttheatmosphere.Theamountofdustproduced,therefiningprocess.

• Itcaneffectthewater,byhavingrunoffcarrythepollutantsuncovered.

ENVIRONMENTALEFFECTSOFUSINGMINERALRESOURCES

• Mineralsareremovedthroughavarietyofmethodsthatvarywidelyintheircosts,safetyfactors,andlevelsofenvironmentalharm.

• Avarietyofmethodsareusedbasedonmineraldepth.– Surfacemining:shallowdepositsareremoved.– Subsurfacemining:deepdepositsareremoved.

Surfacemining– lowtech

• Panningforgold(Placerdeposition)

• Diamondcrawl(Aeolianplacer)

SurfaceMining

• Scooporeoffsurfaceofearth.• cheap.• safeforminers.• largeenvironmentaldestruction.

Open-pitMining

• Circularholeinground,withrampcirclingdownalongsides,allowsdeeperoretobereached

• Machinesdigholesandremoveores,sand,gravel,andstone.

Figure15-11

•Toxicgroundwatercanaccumulateatthebottom.

BinghamCanyonMine

AreaStripMining

• Earthmoversstripsawayoverburden,andgiantshovelsremovesmineraldeposit.

• Oftenleaveshighlyerodiblehillsofrubblecalledspoilbanks.

Figure15-12

SurfaceStripmine

PotashMininginAurora,NC

ContourStripMining

• Usedonhillyormountainousterrain.

• Unlessthelandisrestored,awallofdirtisleftinfrontofahighlyerodiblebankcalledahighwall.

Figure15-13

ContourStripMining

Economics of strip mining depend on stripping ratio

stripping ratio = h1/h2

Thefasterwecandig,themoremoneywecanmake.

MountaintopRemoval

• Machineryremovesthetopsofmountainstoexposecoal.

• Theresultingwasterockanddirtaredumpedintothestreamsandvalleysbelow.

SubsurfaceMining

• Useofshaftstoreachdeeplyburiedores.• expensive.• hazardousforminers.• lessenvironmentaldamage.

• collapse of mine. • fire (methane, coal dust, etc.). • asphyxiation (methane, carbon monoxide, etc.). • pneumoconiosis (from inhaling coal dust). • asbestosis (from inhaling asbestos fibers). • silicosis (from inhaling silicate dust). • heavy metal poisoning (e.g. mercury). • radiation exposure (in uranium mining).

HealthProblems

EnvironmentalDamage• Gapingholesinground(oldopenpitmines).• Pilesofminetailings(non-oreremovedfrommines).

• Contaminationfromheavymetals(e.g.arsenic,mercury)inminetailings.

• Accidentaldrainingofriversandlakes.• Disruptionofgroundwaterflowpatterns.• Lossoftopsoilinstrip-minedregions(350to2,700km2 inUSalone).

EnvironmentalDamage• Contaminationfromsulfuricacid(H2SO4)producedthroughweatheringofironsulfide(FeS2,pyrite)intailings.4FeS2 +14H2O=4Fe(OH)3 +8H2SO4

• Subsidencefromsubsurfacemining

MiningImpacts

• Metaloresaresmeltedortreatedwith(potentiallytoxic)chemicalstoextractthedesiredmetal.

Figure15-15

AcidMineDrainage

• theoutflowof acidic waterfrom(usuallyabandoned) metal minesor coalmines

• Tailings pilesorpondsmaybeasourceofAMD.

AcidMinePrevention

• thewasterockandtailingsfromaminemustbepreventedfromcontactingoxygen

• Preventionisbestsinceminedrainagecanhavelonglastingeffects.

AMDremediation

• LimeNeutralization– Mostcommonmethod– LimeisaddedtoincreasepHto~9tocauseprecipitationofheavymetals

• Othermethodsinclude:– Calciumsilicateneutralization– Carbonateneutralization(limestonechips)– Constructedwetlands(afterlimestoneneutralization)

Smelting and Refining: Extract Pure Commodity from Ore Mineral

• Iron, from an iron oxide (Fe2O3, hematite) rich ore (such as a banded-iron formation, which also contains quartz).

• Coke (carbon from coal), ore, air, and limestone mixed in blast furnace.

1. Production of huge piles of slag. 2. Emission of CO2, a greenhouse gas, into the

atmosphere.3. Pollution associated with the generation of electricity

needed in anode furnaces (especially aluminum).4. Sulfur dioxide emissions from the refining of sulfide

ores are a major source of air pollution. The sulfur dioxide combines with water to produce sulfuric acid.

5. Release of heavy metals (As, Cd, Hg), present in trace quantities in sulfide ores, into the atmosphere.

Smelting and Refining: Environmental Problems

SmeltingPlantAirpollution

H2Odischarge

Toxicwasteproducts

MiningLegislation

• MiningLawof1872– allowedfortherecoveryoforesorfuelsfromfederallands.– Encourageddevelopmentandsettlementofthewest

• SurfaceMiningControlandReclamationActof1977 – regulatessurfaceminingofcoalandthesurfaceeffectsofsubsurfacecoalmining– Requiresminimumdisturbanceduringminingandreclamationafterminingiscomplete.

Reclamation

• Reclamationtimevarieswiththeresilienceoftheecosystem.

Reclamation

• Re-contour/Re-gradetheland• Returntopsoil• Replantappropriateplants(nativesthatfostersuccession)

• Purposeistomakethesoilphysicallystable(minimalerosion,waterinfiltration/retentionreturnstonormal)

Howtoreduceenvironmentalimpact

• Verystrictgovernmentalrules?• Taxes– moneyhelpsreclaimland• Switchtodifferentminerals

•REDUCE,•REUSE,•&RECYCLE