MINERALPROPERTIES,USES,andIDENTIFICATION

part1

AlessandroGrippo,Ph.DPhysicalGeologyLaboratory

WhatareMinerals?

•  Amineralisdefinedas:•  asolid•  thatisnaturallyoccurring•  isinorganic•  iscrystalline•  hasaspecificchemicalcomposiDon

•  hasdisDncDvephysicalproperDes

CrystalsofHalite(TableSalt)fromtheBonnevilleFlats,Wendover,Utah

solidnaturallyoccurring

inorganiccrystalline(formscubes)

hasaspecificchemicalcomposiHon(NaCl)hasitsdisHncHvephysicalproperHes

photo:©AlessandroGrippo

•  Solid–  ifitisagasoraliquid,itisnotamineral

•  Naturallyoccurring–  mineralsformthroughnaturalgeologicprocesses

•  Inorganic–  mineralsarenothydrocarbon-based,likelifeformsare

•  Crystalline–  atomsarearrangedinanorderly,repeaHng,3-DpaPern

•  withaspecificChemicalComposiDon–  composiHonisdescribedbyachemicalformula

•  withdisHncHvePhysicalProperDes–  specificgravity,density,magneHsm,temperaturesandpressuresfor

changeofstate,andmore

Mineralsvs.Rocks

•  Rocksaredefinedas“naturallyformedaggregatesofminerals”

•  Arockcanbecomposedofasinglemineral,ormulHpleminerals

•  Somerocksarecomposedofnon-mineralsubstances

ThisrockisaLIMESTONEItismadeofmulHplecrystalsofone,singlemineral,calledCALCITECaCO3

KelbakerRoad,SanBernardinoCounty,Californiaphoto:©AlessandroGrippo

ThisrockisaGRANITEItismadeofcrystalsofdifferentminerals:blackisBIOTITEK(Fe,Mg)3AlSi3O10(OH)2

grayisQUARTZSiO2whiteisALBITENaAlSi3O8

U.S.395,InyoCounty,Californiaphoto:©AlessandroGrippo

ThisrockisOBSIDIAN,whichisavolcanicglass.

Glassisnotcrystallineandassuchitisnotamineral

ComposiHonisSilicaSiO2

LeeVining,Californiaphoto:©AlessandroGrippo

ThisrockisCOAL,whichismadeofparHallydecomposedorganicmaPer,whichisnotamineral

ComposiHonisCarbonC

RockCollecHonphoto:©AlessandroGrippo

Elements,mineralsandrocks

•  Rocksarecomposedofminerals

•  Mineralsarecomposedofatomsofelementsbondedtogetherinanorderlycrystallinestructure

•  Example:–  therockLIMESTONEismadeofthemineralCALCITE,whichismadeof

oneatomofCa(Calcium),oneatomofC(Carbon)andthreeatomsofO(Oxygen)

–  CaCO3

•  Morethan4700differentkindsofmineralshavebeenidenHfied

•  Onlyabout200mineralsarecommon

•  Mostrocksareformedbyabout20minerals

•  8elementsmakeupthebulkofthose20mineralsinEarth’scrust

The8mostcommonelementsinEarth’scrust

ELEMENT SYMBOLVALENCE,orOXIDATIONNUMBER

%BYWEIGHT

%BYVOLUME

%OFATOMS

Oxygen O -2 46.6 93.8 60.5

Silicon Si +4 27.7 0.9 20.5

Aluminum Al +3 8.1 0.8 6.2

Iron Fe +2(+3) 5.0 0.5 1.9

Calcium Ca +2 3.6 1.0 1.9

Sodium Na +1 2.8 1.2 2.5

Potassium K +1 2.6 1.5 1.8

Magnesium Mg +1 2.1 0.3 1.4

allothers 1.5 3.3

Howdomineralsstaytogether?

•  Mineralsaremadebyatomsofelements•  Atomsaremadebyprotons,neutrons,electrons(subatomicparHcles)

•  Protonsandneutronsresideinthenucleus•  Electronsorbitaroundthenucleusin“shells”•  Dependingonhowmanyelectronsarefoundinshells,differentkindsofchemicalbondsoccur(covalent,ionic,metallic)

ChemicalBonds

•  CovalentBond– whenatomsshareelectrons

•  IonicBond– whenatomsexchangeelectrons

•  MetallicBond– electronsarefreetomovethroughoutthecrystals

•  VanderWaalsBond– weakelectrostaHcbond

OxidaDonNumber,orValence

•  TheOxidaHonNumberofanatomrepresentshowmanyelectronswouldbeneededtohaveacomplete,stableelectronicstructure

•  Itdeterminesthekindofchemicalbond

•  Itdetermineswhoisbondingwithwho

•  Inamineral,thesumofoxidaHonnumbermustbezero!

Polymorphs•  DifferentcrystalstructureswiththesamecomposiHon– commonexamples:

•  GraphiteandDiamondC

•  CalciteandAragoniteCaCO3•  Cristobalite,Tridymite,HighQuartz,LowQuartz,Coesite,SHshovite(Quartz)SiO2

•  Sanidine,Orthoclase,andMicrocline(K-Feldspar)KAlSi3O8

•  Kyanite,Sillimanite,AndalusiteAl2SiO5

hPp://www.tulane.edu/~sanelson/eens211/twinning.htm

Theoutershellofanatomhasspacefor8electrons.

Oxygenonlyhas6electronsintheoutershell.

Withtwomoreelectronsitwouldreachthestageof“fullshell”.

But,ifwehavetwoextraelectrons,theatomwouldhaveacharge,andthatisnotpossible,unlessitbondswithoneormoreotheratoms.

So,Oxygenwouldonlybondwithatomsthatwouldprovideitwithtwoextraelectrons.

ThatwouldimplythatOxygenislookingfortwonegaHvecharges(-2),andthatishowitsOxidaHonNumberiscalculated

Oxygen(-2):anegaDveoxidaDonnumber

•  Calciumonlyhas2electronsintheoutershell.

•  Bylosingthosetwomoreelectronsitwouldreachthestageof“fullshell”.

•  But,ifwelosetwoelectrons,theatomwouldhaveacharge,andthatisnotpossible,unlessitbondswithoneormoreotheratoms.

•  SoCalciumwouldonlybondwithatomsthatwouldtakefromitthosetwoextraelectrons.

•  ThatwouldimplythatcalciumislookingtogiveouttwonegaHvecharges,leavingtwoposiHvecharges(+2)uncovered,andthatishowitsOxidaHonNumberiscalculated

Calcium(+2):aposiDveoxidaDonnumber

hPp://www.micromountain.com/sci_diagrams/at_struct/at_struct_pages/calcium_lab_eng.htm

MineralsGroups

•  Silicates–  containsilica(SiO2),OcombinedwithSi–  OandSiarethemostcommonelementsintheCrust–  SilicatesarethemostcommongroupofmineralsintheEarth’sCrust

• CarbonatescontainthecarbonateionCO3

• SulfatescontainthesulfateionSO4

• SulfidescontainSulfur(S)butnotOxygen(O)S

• OxidescontainOxygen,butnotbondedtoSi(silicates),C(carbonates),orS(sulfates)O

ChloridescontainCl

• NaHveElementsonlyhaveoneelementintheirformulas;examples:Gold(Au),Silver(Ag),Copper(Cu),Diamond(C),Lead(Pb),Zinc(Zn),Tin(Sn),PlaHnum(Pt)andmanymore

SilicatesAlldifferentkindsofsilicatesarebuiltwiththesamebasicunit,whichis

theSiliconTetrahedron

TypesofSilicates•  IsolatedSilicateStructure(tetrahedraarenotconnected)

–  Olivines•  SingleChainSilicates(tetrahedraconnectedtoformsinglechains)

–  Pyroxenes•  DoubleChainSilicates(tetrahedraconnectedtoformdoublechains)

–  Amphiboles•  SheetSilicates(tetrahedraconnectedtoformflatsheets)

–  Micas•  BioHte•  Muscovite

–  Clays•  FrameworkSilicates(tetrahedraconnectedinalldirecHons)

–  Quartz–  Feldspars

•  Ca-Plagioclase•  Na-Plagioclase•  K-Feldspar

Yesbut..HowdoIidenDfymyminerals?

•  ToidenHfyanunknownmineralyoushouldfirstdetermineitsphysicalproperHes

•  ThenyoushoulduseamineralidenHficaHonchart

•  InthenextslidesetwearegoingtodescribethephysicalproperHesofminerals,thetoolsweusetodeterminethem,andhowtousetheidenHficaHonchart

tobeconHnued…