Download MINERAL PROPERTIES, USES, and IDENTIFICATION

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…