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MINERALPROPERTIES,USES,and IDENTIFICATION part1 AlessandroGrippo,Ph.D PhysicalGeologyLaboratory WhatareMinerals? • Amineralisdefinedas: • asolid • thatisnaturallyoccurring • isinorganic • iscrystalline • hasaspecificchemical composiDon • hasdisDncDvephysical properDes CrystalsofHalite(TableSalt) fromtheBonnevilleFlats,Wendover,Utah solid naturallyoccurring inorganic crystalline(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“naturallyformed aggregatesofminerals” • Arockcanbecomposedofasinglemineral,or mulHpleminerals • Somerocksarecomposedofnon-mineral substances ThisrockisaLIMESTONE ItismadeofmulHplecrystalsofone, singlemineral,calledCALCITECaCO3 KelbakerRoad,SanBernardinoCounty,California photo:©AlessandroGrippo ThisrockisaGRANITE Itismadeofcrystalsofdifferentminerals: blackisBIOTITEK(Fe,Mg)3AlSi3O10(OH)2 grayisQUARTZSiO2 whiteisALBITENaAlSi3O8 U.S.395,InyoCounty,California photo:©AlessandroGrippo ThisrockisOBSIDIAN, whichisavolcanicglass. Glassisnotcrystallineandassuch itisnotamineral ComposiHonisSilicaSiO2 LeeVining,California photo:©AlessandroGrippo ThisrockisCOAL, whichismadeofparHallydecomposed organicmaPer,whichisnotamineral ComposiHonisCarbonC RockCollecHon photo:©AlessandroGrippo Elements,mineralsandrocks • Rocksarecomposedofminerals • Mineralsarecomposedofatomsofelements bondedtogetherinanorderlycrystalline structure • Example: – therockLIMESTONEismadeofthemineralCALCITE,whichismadeof oneatomofCa(Calcium),oneatomofC(Carbon)andthreeatomsof O(Oxygen) – CaCO3 • Morethan4700differentkindsofminerals havebeenidenHfied • Onlyabout200mineralsarecommon • Mostrocksareformedbyabout20minerals • 8elementsmakeupthebulkofthose20 mineralsinEarth’scrust The8mostcommonelementsinEarth’scrust ELEMENT SYMBOL VALENCE,or OXIDATION NUMBER 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 %BY WEIGHT %BY VOLUME %OF ATOMS 1.5 3.3 Howdomineralsstaytogether? • Mineralsaremadebyatomsofelements • Atomsaremadebyprotons,neutrons, electrons(subatomicparHcles) • Protonsandneutronsresideinthenucleus • Electronsorbitaroundthenucleusin“shells” • Dependingonhowmanyelectronsarefound inshells,differentkindsofchemicalbonds occur(covalent,ionic,metallic) ChemicalBonds • CovalentBond – whenatomsshareelectrons • IonicBond – whenatomsexchangeelectrons • MetallicBond – electronsarefreetomovethroughoutthecrystals • VanderWaalsBond – weakelectrostaHcbond OxidaDonNumber,orValence • TheOxidaHonNumberofanatomrepresents howmanyelectronswouldbeneededtohave acomplete,stableelectronicstructure • Itdeterminesthekindofchemicalbond • Itdetermineswhoisbondingwithwho • Inamineral,thesumofoxidaHonnumber mustbezero! Polymorphs • Differentcrystalstructures withthesamecomposiHon – commonexamples: • GraphiteandDiamondC • CalciteandAragoniteCaCO3 • Cristobalite,Tridymite,High Quartz,LowQuartz,Coesite, SHshovite(Quartz)SiO2 • Sanidine,Orthoclase,and Microcline(K-Feldspar)KAlSi3O8 • Kyanite,Sillimanite,Andalusite Al2SiO5 hPp://www.tulane.edu/~sanelson/eens211/twinning.htm Oxygen(-2): anegaDveoxidaDonnumber Theoutershellofanatomhasspacefor 8electrons. Oxygenonlyhas6electronsintheouter shell. Withtwomoreelectronsitwouldreach thestageof“fullshell”. But,ifwehavetwoextraelectrons,the atomwouldhaveacharge,andthatis notpossible,unlessitbondswithoneor moreotheratoms. So,Oxygenwouldonlybondwithatoms thatwouldprovideitwithtwoextra electrons. ThatwouldimplythatOxygenislooking fortwonegaHvecharges(-2),andthatis howitsOxidaHonNumberiscalculated Calcium(+2): aposiDveoxidaDonnumber hPp://www.micromountain.com/sci_diagrams/at_struct/at_struct_pages/calcium_lab_eng.htm • Calciumonlyhas2electronsintheouter shell. • Bylosingthosetwomoreelectronsit wouldreachthestageof“fullshell”. • But,ifwelosetwoelectrons,theatom wouldhaveacharge,andthatisnot possible,unlessitbondswithoneormore otheratoms. • SoCalciumwouldonlybondwithatoms thatwouldtakefromitthosetwoextra electrons. • Thatwouldimplythatcalciumislookingto giveouttwonegaHvecharges,leavingtwo posiHvecharges(+2)uncovered,andthat ishowitsOxidaHonNumberiscalculated MineralsGroups • Silicates – containsilica(SiO2),OcombinedwithSi – OandSiarethemostcommonelementsintheCrust – Silicatesarethemostcommongroupofmineralsinthe Earth’sCrust • Carbonates containthecarbonateionCO3 • Sulfates containthesulfateionSO4 • Sulfides containSulfur(S)butnotOxygen(O)S • Oxides containOxygen,butnotbondedtoSi (silicates),C(carbonates),orS(sulfates)O Chlorides containCl • NaHveElements onlyhaveoneelementintheirformulas; examples:Gold(Au),Silver(Ag),Copper (Cu),Diamond(C),Lead(Pb),Zinc(Zn),Tin (Sn),PlaHnum(Pt)andmanymore Silicates Alldifferentkindsofsilicatesarebuiltwiththesamebasicunit,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? • ToidenHfyanunknownmineralyoushouldfirstdetermine itsphysicalproperHes • ThenyoushoulduseamineralidenHficaHonchart • Inthenextslidesetwearegoingtodescribethephysical properHesofminerals,thetoolsweusetodeterminethem, andhowtousetheidenHficaHonchart tobeconHnued…