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Chapter 02
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Eastern Visayas State University
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arthscrustandoceansarethesourceofawidevarietyofusefulandessentialminerals peoplearefamiliarwiththecommonusesofmanybasicmetals,includingaluminuminbever- agecans,copperinelectricalwiring,andgoldandsilverinjewelry awarethatpencilleadcontamsthegreasy-feelingmineralgraphiteandthatbathpowdersandmany cosmeticscontainthemineraltalcMoreover,manydonotknowthatdrillbitsimpregnatedwithdia- mondsareemployedbydentiststodrillthroughtoothenamel,orthatthecommonmineralquartzis thesourceofsiliconforcomputerchips Infact,practicallyeverymanufacturedproductcontains materialsobtainedfromminerals
FOCUSomCONCEPTS Toassistyouinlearningtheimportantconceptsin thischapter,focusonthefollowingquestions: Whatareminerals,andhowaretheydifferentfromrocks? Whatarethesmallestparticlesofmatter’? Howdoatomsbond? Howdoisotopesofthesameelementvary,andwhyaresomeisotopesradioactive? Whataresomeofthephysicalandchemicalpropertiesofminerals?Howcanthesepropertiesbeusedtodis- tinguishonemineralfromanother? WhataretheeightelementsthatmakeupmostofEarth'scontinentalcrust? Whatisthemostabundantmineralgroup? Whatdoallsilicatemineralshaveincommon? Whatarerenewableandnonrenewableresources? Whenisthetermoreusedwithreferencetoamineral?
Minerals Building
Blocks ofRocks
EarthMaterials ‘Rm->""2:Z-iOIrn bMinerals
WebeginourdiscussionofEarthmaterialswithanoverview ofmineralogy(mineral=mineral,ology=thestudyof) becauseminerals arethe buildingblocksofrocks In addition,mineralshavebeenemployedbyhumansfor bothusefulanddecorativepurposesforthousandsof years( iii» i)Thefirstmineralsimnedwereflintand chert,whichpeoplefashionedintoweaponsandcutting toolsAsearlyas 3700 Bc,Egyptiansbeganmininggold silver,andcopper,andby 2200 Bchumansdiscoveiedhow tocombinecopperwithtintomakebronze,astrong,hard alloyLater,humansdevelopedaprocesstoextractironfrom mineralssuchashematite—adiscoverythatmarkedthe declineoftheBronzeAge Byabout 800 Bc,iron-working technologyhadadvancedto thepointthatweaponsandmany everydayOb]€C'[Sweremadeofiionratherthancopper,bronze,or woodDuringtheMiddleAges,miningofavarietyofminerals
1%.::-i Collectionofwell-developedquartzcrystalsfoundnear HotSprings,Arkansas(PhotobyJeffScovii)
wascommonthroughoutEuropeandtheimpetusfortheformal studyofmineralswasinplace. Thetermmiriercilisusedinseveraldifferentways example,thoseconcernedwithhealthandfitnessextolthe benefitsofvitaminsandminerals- callyusesthewordwhenreferringtoanythingtakenoutofthe
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30 CHAPTER 2 MatterandMinerals
Granite PropertiesofProtons, (Rock)
Quartz Hornblende
(Mineral) (Mineral)
f;F'ii?Ui~:iii Mostrocksareaggregatesoftwoormoreminerals.
Shownhereisahandsampleoftheigneousrockgraniteandthreeof
itsmajorconstituentminerals.(PhotosbyE)
####### CONCEPTCHECK 2.
QListfivecharacteristicsthatclassifyanEarthmaterialasa mineral. QBasedonthedefinitionofamineral,whichofthefollowing materialsarenotclassifiedasminerals,andwhy:gold,water, syntheticdiamonds,ice,andwood. QDefinethetermrock?
Atoms: Building
Blocks ofMinerals
Whenmineralsare carefullyexamined,evenunderoptical microscopes,theinnumerabletinyparticlesoftheirinternal structures are not discernable. Nevertheless, all matter, includingminerals,iscomposedofminutebuildingblocks calledatoms—thesmallestparticlesthatcannotbechemically split—protonsand neutronslocatedinacentralnucleusthatissurroundedby electrons(Figure‘Z.éi).
Fit?-‘Bi-tiil.211Twomodelsoftheatom of theatom encircledbyhigh-speedelectrons theatomshows electronclouds(shells)surroundingacentralnucleus containsvirtuallyallof themassoftheatom atomisthespaceinwhichthelight,negativelychargedelectrons reside.(Therelativesizesofthenucleishownaregreatly exaggerated.)
Neutrons,andElectrons Protonsandneutronsareverydenseparticleswithalmost identicalmasses,electronshaveanegligible mass,about1/2000ththatofaproton,ifa protonoraneutronhad themassofabaseball,anelectron wouldhavethemassofasinglegrainofrice. Bothprotonsandelectronsshareafundamentalprop- ertycalledelectricalcharge of+1,andelectronshaveachargeof—1,asthe namesuggests,havenocharge electronsareequalinmagnitudebutoppo- siteinpolarity,sowhenthesetwoparti- %‘5-Q- -.<:‘-1--=,'\‘§."';. r,'L‘'P“Zfr-I_<"‘-s'-";~ w.- clesarepaired,thechargescanceleach other equalnumbersofpositivelycharged protons andnegatively charged electrons, most substances are electricallyneutral. Feldspar Inillustrations, electronsare (Minera') sometimes shown orbiting the nucleusinamannerthatresemblestheplanetsofoursolarsys- temorbitingtheSun(Figure2).However,electronsdonot actuallybehavethisway- tronsasacloudofnegativechargessurroundinganucleus
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Atoms:BuildingBlocksofMinerals 31
StudentsSometimesAsk...
Arethemineralsyoutalkedaboutinclassthesameas thosefoundindietarysupplements? Notordinarily mineralstypicallycontain perspective,amineralmustbe elementsthataremetals— anaturallyoccurringcrystalline calcium,potassium, solid phosphorus,magnesium,and supplementsarehuman-made iron inorganiccompoundsthat vitaminsareorganic containelementsneededto compoundsnotinorganic sustainlife compounds,likeminerals.
(Figure2).Studiesofthearrangementsofelectronsshowthat theymoveaboutthenucleusinregionscalledprincipalshells, eachwithanassociatedenergylevel,eachshellcan holdaspecificnumberofelectrons,withtheoutermostshell containingvalenceelectronsthatinteractwithotheratomsto formchemicalbonds. Mostoftheatomsintheuniverse(excepthydrogenand helium)werecreatedinsidemassivestarsbynuclearfusionand releasedintointerstellarspaceduringhot,fierysupernova
:.1 1"; Periodictableoftheelements.
Tendencyto loseoutermost electrons touncoverfull
explosions,thenewlyformed nucleiattractedelectronstocompletetheiratomicstructure thetemperaturesfoundatEarth’ssurface,allfreeatoms(not bondedtootheratoms)haveafullcomplementofelectrons- oneforeachprotoninthenucleus.
Elements: DefinedbyTheir NumberofProtons Thesimplestatomshaveonlyoneprotonintheirnuclei,whereas othershavemorethan100 ofanatom,calledtheatomicnumber,determinesitschemical nature chemicalandphysicalproperties,agroupofthesame kindofatomsiscalledanelement 90 naturally occurringelementsand 23 thathavebeensynthesized probablyfamiliarwiththenamesofmanyelementsincluding carbon,nitrogen,andoxygen, allnitrogenatomshavesevenprotons,andalloxygenatomshave eightprotons. Elementsareorganizedsothatthosewithsimilarproperties lineupincolumns,calledtheperiodictable, isshownin -< Eachelementhasbeenassignedaone-or two-lettersymbol includedforeachelement.
Noble OuterShe“ -"Metals Tendency gases /W/W Atomicnumber
- 1 He 2 ~/K/Symbolofelement 10080 H HBIIUH14-0<+Atomicweight Hydrogen Nameofelement
togain (meftl Transitionmetals Tendencytofill electrons r—)% Nonmetals 0'-49"Shellby tomakefull W,A Noblegases sharingAelectrons outerAshell 2 T _ _ / / \ ; Lanthanideseries 4 ii IA IIA IActinjdeSeries lIIA IVA VA VIA VIIA Helium 3 4 ii Li Be Lithium6 Beryllium,9 I
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5 5 7 9 9 10 g F Ne 5 Fluorine18 20 :,
B C N O Boron10 Carbon12 Nitrogen14 15 11. 12 , 17 18 Na 1 Mp 1/ Sodium22- 5 Magnesium24, 1 E IllB 19 - 20 21 22 K Ca ’ Sc 4Ti V 1 Cr Mn Fe C 39 0 44 7.
IVB VB VIB VIIB iiVIIIBii IB llB Aluminum Silicon Phosphorus Sulfur 23 24 25 26 27 28 29 30 31 50 I 52 54 55 59 59. 55 55 99.
13 14 15 16 26 28 30 32 35 39 Chlorine Argon 32 33 34 35 36 Ni Cu Zn Ga I Ge As Se Br Kr Potassium Calcium 4 Scandium Titanium VanadiumChromiumManganese Iron Cobalt Nickel _ Copper Zinc Galliumgermanium72,59 Arsenic74 Selenium78 Bromine79 Krypton83. 37 ’ 38 39 40 41 1 42 43 44 45 ' 46 ' 47 48 _ 49 50 - 51 52 53 54 : 119' 121 127 125. .0 = 95 -. 97 f 99 91 92. 95,94MO TC(99) 101 102 105 ' 101?Ag 112 114 Sn Sb Te I 90 1515 Xe ' RubidiumIStrontium. Yttrium Zirconium NiobiumMolybdenurnTechnetium'RutheriiumRhodium Palladiunr Silver Cadmium Indium ' "Fin Antimony Tellurium Iodine Xenon 55 56 #57 72 73 74 75 76 77 78 79 80 81 ' _ 132 I' 137 ‘ T0 178 Hf 49 180 Ta 95 183 85W. 186 Re 2 190 Os 2 192 2Ir 195 Pt 09. 197 Au 0 200 Hg 9 204 Tl 37 I Pb P Bi Po (210)At (2Fin) I Cesium. Barium #7-I Hafnlurn Tantalum Tungsten Rheniurn Osmium iridium Platinum Gold Mercury Thallium- Lead .Bisrnuth Poloniurn Astatine Radon
99 94 95 95 , 207 208 (210) 22
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Atoms:BuildingBlocksofMinerals 33
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REChemicalbondingofsodiumchloride(tablesalt). A atomtoachlorineatom,sodiumbecomesapositiveionandchlorine anegativeion(packing)of sodiumandchlorineionsintablesalt.
shell,chlorine(which hassevenvalenceelectrons)gainstheeighthelectronneeded to completeitsoutermostshell,throughthetransferofasin- gleelectron,boththesodiumandchlorineatomshaveacquired astableelectronconfiguration. Afterelectrontransfertakesplace,theatomsarenolongerelec- tricallyneutral,aneutralsodiumatom becomespositivelycharged(with 1 Iprotonsand 10 electrons).Sim- ilarly,byacquiringoneelectron,aneutralchlorineatombecomes negativelycharged(with1'7protonsand 18 electrons).Weknow thationswithlikechargesrepel,andthosewithunlikecharges attract,anionicbondistheattractionofoppositelycharged ionstooneanother,producinganelectricallyneutralcompound. Figure2 ionsinordinarytablesalt sodiumandchlorineions,positionedinsuchamannerthateach positiveionisattractedtoandsurroundedonallsidesbynegative ions,andviceversa betweenionswithoppositechargeswhileminimizingtherepul- sionbetweenionswithidenticalcharges,ioniccompounds consistofanorderlyarrangementofoppositelychargedions assembledinadefiniteratiothatprovidesoverallelectricalneu- trality.
Thepropertiesofachemicalcompound aredramaticallydifferentfromtheproper- tiesofthevariouselementscomprisingit. Forexample,sodiumisasoftsilverymetal thatisextremelyreactiveandpoisonous. .- Ifyouweretoconsumeevenasmall amountofelementalsodium,youwould needimmediatemedicalattention- rine,agreenpoisonousgas,issotoxic thatitwasusedasachemicalweapon duringWorldWarI,however, theseelementsproducesodiumchloride, aharmlessflavorenhancerthatwecalltable salt,whenelementscombinetoform compoundstheirpropertieschangesignificantly.
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CovalentBonds:Electrons Shared Sometimestheforcesthatholdatomstogether cannotbeunderstoodonthebasisoftheattraction ofoppositelychargedions hydrogen molecule (H2), in which the two hydrogenatomsareheldtogethertightlyandno ionsarepresent holdstwohydrogenatomstogetherresultsfroma covalentbond, achemicalbondformedbythe sharingofapairofelectronsbetweenatoms. Imaginetwohydrogenatoms(eachwithonepro- tonandoneelectron)approachingoneanothersothattheirelec- troncloudsoverlap(?Eig1ire¥i.§.i).Oncetheymeet,theelectron configurationwillchangesothatbothelectronswillprimarily occupythespacebetweentheatoms,thetwoelec- tronsaresharedbybothhydrogenatomsandattractedsimulta- neouslybythepositivechargeoftheprotoninthenucleusofeach atom theseatomstogether- ecules,theforcethatholdstheseatomstogetherarisesfromthe attractionofoppositelychargedparticles—protonsinthenuclei andelectronssharedbytheatoms.
MetallicBonds:ElectronsFreetoMove Inmetallicbonds,thevalenceelectronsarefreetomovefrom oneatomtoanothersothatallatomssharetheavailablevalence electrons, gold,aluminum,andsilver,andinalloyssuchasbrassandbronze. Metallicbondingaccountsforthehighelectricalconductivityof metals,theeasewithwhichmetalsareshaped,andnumerous otherspecialproperties.
####### CONCEPTcnccrc 2.
QWhatisthedifferencebetweenanatomandanion? QWhatoccursinanatomtoproduceapositiveion?Anegative ion? QBrieflydistinguishbetweenionicandcovalentbondingand therolethatelectronsplayinboth.
34 CHAPTER2 MatterandMinerals
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H Hydrogenmolecule 1 -a-,=,'.-‘-1-=.,T_'li@:=i.;.1;Yi:.:-5}Formationofacovalentbondbetweentwohydrogen atoms(H)toformahydrogenmolecule(H2).Whenhydrogenatoms bond,theelectronsaresharedbybothhydrogenatomsandattracted simultaneouslybythepositivechargeof theprotoninthenucleusof eachatom (bonds)theseatomstogether.
Isotopes andRadioactive
Decay
Themassnumberofanatomissimplythetotalntunberofitspro- tonsandneutrons numberofprotons,buttheymayhavevaryingnumbersofneutrons. Atomswiththesamenumberofprotonsbutdifferentnumbersof neutronsareisotopesofthatelement arelabeledbyplacingthemassntunberaftertheelement’snameor symbol,carbonhasthreewell-knownisotopes hasamassntunberof 12 (carbon-12),anotherhasamassnumber ofI3(carbon-13),andthethird,carbon-14,hasamassnumber of14-12mustalsohavesixneutronstogiveitamassnum- berof12-14,ontheotherhand,hassixprotonspluseight neutronstogiveitamassnumberof14. Inchemicalbehavior,allisotopesofthesameelementare nearlyidentical- ferentiateidenticaltwins,withoneweighingslightlymorethan theother chemicalbehavior,theyoftenbecomepartsofthesamemineral. Forexample,whenthemineralcalcite(CaCO3)forms,someof itscarbonatomsarecarbon-12,andsomearecarbon-14. Thenucleiofmostatomsarestable,manyelements dohaveisotopesinwhichthenucleiareunstable—carbon- 14 is oneexampleofanunstableisotope,unstable
meansthatthenucleichangethrougharandomprocesscalled radioactivedecay,unstableisotopes radiateenergyandemitparticles- topesdecayaremeasurable,certainradioactiveatoms areusedtodeterminetheagesoffossils,rocks,andminerals. Adiscussionofradioactivedecayanditsapplicationsindating pastgeologiceventsappearsinChapterll.
CONCEPTcnrzcx 2. QWhatisanisotope? QNameoneisotopeofcarbonthatisunstable. QIfthenumberofelectronsinaneutralatomis 35 anditsmass numberis80,calculatethefollowing: a. thenumberofprotons b. theatomicnumber c. thenumberofneutrons
Properties ofMinerals
EarthMaterials
‘hm92>F":2—\nzr! PMinerals Minerals have definite crystalline structures and chemical compositionsthatgivethemuniquesetsofphysicalandchemical propertiessharedbyallsamplesofthatmineral,all specimensofhalitehavethesamehardness,thesamedensity,and breakinasimilarmanner’sinternalstructure andchemicalcompositionaredifficulttodeterminewithoutthe aid of sophisticatedtests and equipment, themore easily recognizedphysicalpropertiesarefrequentlyusedinidentification.
OpticalProperties Ofthemanyopticalpropertiesofminerals—theirluster,their abilitytotransmitlight,theircolor,andtheirstreak—aremost frequentlyusedformineralidentification.
Luster Theappearanceorqualityoflightreflectedfromthe surfaceofamineralisknownasluster appearanceofmetals,regardlessofcolor,aresaidtohavea metallicluster Somemetallicminerals,suchas
Thefreshlybrokensampleofgalena(right)displaysa metallicluster,whilethesampleontheleftistarnishedandhasa submetallicluster.(PhotocourtesyofE)
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36 CHAPTER 2 MatterandMinerals
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Pititl;§;.'i:I%Althoughmostmineralsexhibitonlyonecommon crystalshape,some,suchaspyrite,havetwoormorecharacteristic habits.(PhotosbyDennisTasa)
direction,orflattenedifgrowthinonedimensionissuppressed. Commonlyusedtermstodescribetheseandothercrystalhabits include equant (equidimensional), bladed,fibrous, tabular, prismatic,platy,bloclcy,andbotryoidal picturedinFigure2:14.
MineralStrength
Howeasilymineralsbreakordeformtmderstressisdetermined bythetypeandstrengthofthechemicalbondsthatholdthe crystalstogether, hardness,cleavage,andfracturetodescribemineralstrengthand howmineralsbreakwhenstressisapplied.
FiGiiRE2.14.Somecommoncrystalhabits.A crystalsthatareflattenedinonedirection.B crystalswithfacesthatareparalleltoacommondirection. Mineralsthathavestripesorbandsofdifferentcolorortexture. D ofgrapes.(PhotosbyDennisTasa)
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C D
Tenacity Thetermtenacitydescribesamineral’stoughness, oritsresistancetobreakingordeforming ionicallybonded,suchasfluoriteandhalite,tendtobebrittle andshatterintosmallpieceswhenstruck,minerals withmetallicbonds,suchasnativecopper,aremalleable,or easilyhammeredintodifferentshapes,including gypsumand talc,thatcan becut intothinshavings are describedassectile,notablythemicas,areelastic andwillbendandsnapbacktotheiroriginalshapeafterthe stressisreleased.
Hardness Oneofthemostusefuldiagnosticpropertiesis hardness,ameasureoftheresistanceofamineraltoabrasionor scratching unknownhardnessagainstoneofknownhardness,orviceversa. Anumericalvalueofhardnesscanbeobtainedbyusingthe Mohsscaleofhardness,whichconsistsof 10 mineralsarranged inorderfrom 1 (softest)to 10 (hardest),asshowninFigure rm... ItshouldbenotedthattheMohsscaleisarelativeranking,and itdoesnotimplythatmineralnumber2,gypsum,istwiceashard
‘i+‘i#I;%URl-.iiZyiiiHardnessscales,withthe hardnessofsomecommonobjects relativehardnessscaleandanabsolutehardnessscale.
A(Relativehardness)‘; Diamondm_LC3 ‘Pf Corundumi 9 Topaz—-?— 8 ‘ Quartzit 7 Streakplate(6) - Orthoclasei~ 6 * ., Glass&knifeblade(5) i Apatite?— 5 I, Wirenail(4) Fluorite———— 4 ll "illCopperpenny(3) Calcite?— 3 Fingernail(2) , Gypsum———- 2 * _ y Talc—?—_____l 1 l INDEXMINERALS COMMONOBJECTS
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PropertiesofMinerals 37
Students SometimesAsk...
Arethereanyartificialmaterialsharderthandiamonds‘? Yes,butyouwon’tbeseeing carbonatoms—relativesofthe themanytimesoon famous“buckyballs"—also ofcarbonnitride(C3N4), couldbeashardasadiamond. describedin 1989 and Thesematerialsareexpensive synthesizedinalaboratory toproduce,sodiamonds shortlythereafter,maybe continuetobeusedas harderthandiamondbuthasn’t beenproducedinlargeenough amountsforapropertest 1999,researchersdiscovered since1955,arenowwidely thataformofcarbonmadefrom usedintheseindustrial fusedspheresof 20 and 28 applications.
abrasivesandincertain kindsofcuttingtools. Syntheticdiamonds,produced
asminerall,talc,gypsumisonlyslightlyharderthantalc, asFigure2. Inthelaboratory,othercommonobjectscanbeusedto determinethehardnessofamineral fingernail,whichhasahardnessofabout2,acopperpenny (3),andapieceofglass(5).Themineralgypsum,whichhas ahardnessof2,canbeeasilyscratchedwithafingernail theotherhand, themineralcalcite,whichhasahardnessof3, willscratchafingernailbutwillnotscratchglass,one ofthehardestcommonminerals,willeasilyscratchglass. Diamonds,hardestofall,scratchanything,includingother diamonds.
Cleavage Inthecrystalstructureofmanyminerals,some atomicbondsareweakerthanothers thatmineralstendtobreakwhentheyarestressed (Kleiben=carve)isthetendencyofamineraltobreak(cleave) alongplanesofweakbonding,but thosethatdocanbeidentifiedbytherelativelysmooth,flatsur- facesthatareproducedwhenthemineralisbroken. Thesimplesttypeofcleavageisexhibitedbythemicas a).Becausethesemineralshaveveryweakbondsin onedirection,theycleavetoformthin,flatsheets- eralshaveexcellentcleavageinone,two,three,ormoredirec- tions,whereasothersexhibitfairorpoorcleavage,andstill othershavenocleavageatall morethanonedirection,cleavageisdescribedbythenumber ofcleavagedirectionsandtheangle(s)atwhichtheymeet .=.-:5; :2... Eachcleavagesurfacethathasadifferentorientationis countedasadifferentdirectionofcleavage,some mineralscleavetoformsix-sidedcubes definedbythreedifferentsetsofparallelplanesthatintersectat 90-degreeangles,cleavageisdescribedasthreedirectionsofcleav- agethatmeetat 90 degrees. Donotconfusecleavagewithcrystalshape exhibitscleavage,itwillbreakintopiecesthatallhavethesame geometry,thesmooth-sidedquartzcrystalsshown inFigure2(p)illustratecrystalshaperatherthancleavage.
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<i> Strongbond Thethinsheetsshownherewereproducedbysplitting amica(muscovite)crystalparalleltoitsperfectcleavage.(PhotobyChip Clark)
Ifbroken,theyfractureintoshapesthatdonotresembleone anotherortheoriginalcrystals.
Fracture Mineralshavingchemicalbondsthatareequally,or nearlyequally,stronginalldirectionsexhibitapropertycalled fracture,mostproduceunevensurfaces andaredescribedasexhibitingirregularfracture,some minerals,suchasquartz,breakintosmooth,curvedsurfaces resemblingbrokenglass arecalledconchoidal fractures ms).Stillothermineralsexhibitfracturesthat producesplintersorfibersthatarereferredtoassplinteryand fibrousfiacture,respectively.
DensityandSpecificGravity Density,animportantpropertyofmatter,isdefinedasmassper unitofvolumeandisoftenexpressedingramspercubiccen- timeter(g/cm3).Mineralogistsoftenusearelatedmeasurecalled specificgravitytodescribethedensityofminerals gravityisanumberrepresentingtheratioofamineral’sweight totheweightofanequalvolumeofwater waterequals1. Mostcommonrock-formingmineralshaveaspecificgravity ofbetween 2 and3,quartzhasaspecificgravityof 2,somemetallicmineralssuchaspyrite,native copper,andmagnetitearemorethantwiceasdenseandthus havemorethantwicethespecificgravityasquartz,an oreoflead,hasaspecificgravityofroughly7,whereasthespe- cificgravityof24-karatgoldisapproximately20. Withalittlepractice,youcanestimatethespecificgravityofa mineralbyheftingitinyourhand,doesthismineral
MineralGroups 39
FIGURE2 Conchoidalfracture,curvedsurfacesresult whenmineralsbreakinaglasslikemanner.(PhotocourtesyofE)
mineralsurface,certainminerals,called carbonates,willeffervesce(fizz)ascarbondioxidegasisreleased (Figure2).Thistestisespeciallyusefulinidentifyingthecom- moncarbonatemineralcalcite.
.concsPrcensor; 2.
QDefineluster. QWhyiscolornotalwaysausefulpropertyinmineralidentifi- cation?Giveanexampleofamineralthatsupportsyour answer. QWhatismeantwhenwerefertoamineral'stenacity?List threetermsthatdescribetenacity. QWhatdifferentiatescleavagefromfracture? QWhatsimplechemicaltestisusefulintheidentificationofthe mineralcalcite?
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Mineral Groups
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Over4,000mineralshavebeennamed,andseveralnewonesare identifiedeachyear,forstudentswhoarebeginning tostudyminerals,nomorethanafewdozenareabundant! Collectively,thesefewmakeupmostoftherocksofEarth’scrust and,assuch,areoftenreferredtoastherock-formingminerals. Althoughlessabundant,manyothermineralsareusedexten- sivelyinthemanufactureofproductsandarecalledeconomic minerals,rock-formingmineralsandeconomicminer- alsarenotmutuallyexclusivegroups deposits,somerock-formingmineralsareeconomicallysignifi- cant,whichistheprimary componentofthesedimentaryrocklimestoneandhasmanyuses includingbeingusedintheproductionofcement. Itisworthnotingthatonlyeightelementsmakeupthevast majorityoftherock-formingmineralsandrepresentmorethan 98 percent(byweight)ofthecontinentalcrust(Figure2). Theseelements,inorderofabundancefrommosttoleast,are oxygen(O),silicon(Si),aluminum(Al),iron(Fe),calcium(Ca), sodium(Na),potassium(K),andmagnesium(Mg).Asshown inFigure2,siliconandoxygenarebyfarthemostcommon
EarthMaterials PMinerals ‘gm->"IxZ-lHII
40 CHAPTER 2 MatterandMinerals
- .- __. - .. - —
l'V|-pi;:'l'-f."J'{-'JE'---,,-'1' ':' -2'|! l
ummum 8% Other —elements 1% Calcium(Ca) 3%'
Iron(Fe) 5% Potassium(K) Sodium(Na) 2% Magnesium(Mg) 2% 2% Relativeabundanceoftheeightmostcommon elementsinthecontinentalcrust.
elementsinEarth’scrust,thesetwoelementsread- ilycombinetoformthebasic“buildingblock”forthemostcom- monmineralgroup, the silicates. More than 800 silicate mineralsareknown,andtheyaccountformorethan 90 percent ofEarth’scrust. Becauseothermineralgroupsarefarlessabundantin Earth’scrustthanthesilicates,theyareoftengroupedtogether undertheheadingnonsilicates silicates,somenonsilicatemineralsareveryimportanteco- nomically ourautomobiles,gypsumforplasteranddrywallforhomecon- struction,andcopperwirethatcarrieselectricityandconnects usto theInternet includethecarbonates,sulfates,andhalides theireconomicimportance,thesemineralgroupsinclude membersthataremajorconstituentsinsedimentsandsedi- mentaryrocks. Wefirstdiscussthemostcommonmineralgroup,thesilicates, andthenconsidersomeoftheprominentnonsilicatemineral groups.
SilicateMinerals
Eachofthesilicatemineralscontainsoxygenandsiliconatoms. Exceptforafewsilicatemineralssuchasquartz,mostsilicate mineralsalsocontainoneormoreadditionalelementsintheir crystallinestructure ofsilicatemineralsandtheirvariedproperties. Allsilicateshavethesamefundamentalbuildingblock,the silicon-oxygen tetrahedron (tetra=four,hedra=abase). Thisstructureconsistsoffouroxygenatomssurroundingamuch smallersiliconatom,asshownin‘i"it;r.=;i.*a Insomeminerals, thetetrahedraarejoinedintochains,sheets,orthree-dimensional networksbysharingoxygenatoms Theselarger silicatestructuresarethenconnectedtooneanotherbyother elements
iron(Fe),magnesium(Mg),potassium(K),sodium(Na),and calcium(Ca). Majorgroupsofsilicatemineralsandcommonexamplesare giveninFigure2 group,comprisingover 50 percentofEarth’scrust,the secondmostabundantmineralinthecontinentalcrust,isthe onlycommonmineralmadecompletelyofsiliconandoxygen. NoticeinFigure2 silicatestructure structureofamineralandthecleavageitexhibits silicon—oxygenbondsarestrong,silicatemineralstendtocleave betweenthesilicon-oxygenstructuresratherthanacrossthem. Forexample,themicashaveasheetstructureandthustendto cleaveintoflatplates(seemuscoviteinFigure2).Quartz,which hasequallystrongsilicon-oxygenbondsinalldirections,hasno cleavagebutfracturesinstead. Howdosilicatemineralsform?Mostcrystallizefrommolten rockasitcools’ssurface (lowtemperatureandpressure)oratgreatdepths(hightemper- atureandpressure).Theenvironmentduringcrystallizationand thechemicalcompositionofthemoltenrockmainlydetermine whichmineralsareproduced,thesilicatemineral olivinecrystallizesathightemperatures(about1200°C[2200°F]), whereasquartzcrystallizesatmuchlowertemperatures(about 700°C[1300°F]). Inaddition,somesilicatemineralsformatEarth’ssurfacefrom theweatheredproductsofothersilicateminerals areanexample extremepressuresassociatedwithmountainbuilding- catemineral,therefore,hasastructureandachemicalcomposition thatindicatetheconditionsunderwhichitformed,bycarefully examiningthemineralmakeupofrocks,geologistscanoftendeter- minethecircumstancesunderwhichtherocksformed.
Tworepresentationsofthesilicon-oxygentetrahedron. A,andthebluesphere representsasiliconion radiioftheions oxygenionateachofthefourcorners.
814*
/Si“
A stor- 4
42 CHAPTER 2 MatterandMinerals
Students SometimesAsk...
Arethesesilicatesthesamematerialsusedinsilicon computerchipsandsiliconebreastimplants? Notreally,butallthreecontain theelementsilicon(Si). Furthermore,thesourceof siliconfornumerousproducts, includingcomputerchipsand breastimplants,comesfrom silicateminerals (withouttheoxygenthat silicateshave)isusedtomake computerchips,givingriseto theterm“SiliconValley"for thehigh-techregionofSan Francisco,California’ssouth bayarea,wheremanyofthese devicesaredesigned.
Manufacturersofcomputer chipsengravesiliconwafers withincrediblynarrow conductivelines,squeezing millionsofcircuitsintoevery fingernail-sizechip. Si1icone—thematerialused inbreastimplants—isasilicon- oxygenpolymergelthatfeels rubberyandiswater repellent,chemicallyinert,and stableatextremetemperatures. Concernaboutthelong-term safetyoftheseimplantslimited theiruseafter1992.
TABLE2 CommonNonsilicateMineralGroups
ImportantNonsilicateMinerals Althoughnonsilicatesmakeuponlyabout 8 percentofEarth’s crust, someminerals,suchasgypsum,calcite,andhalite,aremajor constituentsinsedimentaryrocks,manyothersare importanteconomically mineralclassesandafewexamplesofeach commonnonsilicatemineralsbelongtooneofthreeclassesof minerals—thecarbonates(CO32T),thesulfates(SO,,2_),andthe halides((3111F1“,sir). Thecarbonatemineralsaremuchsimplerstructurally thanthesilicates- bonateion(CO32T)andoneormorekindsofpositiveions mostcommoncarbonatemineraliscalcite,CaCO3(calcium carbonate).Thismineralisthemajorconstituentintwowell- knownrocks:limestoneandmarble uses,includingasroadaggregate,asbuildingstone,andas the mainingredientinPortlandcement is used decoratively. Twoothernonsilicatemineralsfrequentlyfoundinsedi- mentaryrocksarehaliteandgypsum- monlyfoundinthicklayersthatarethelastvestigesofancient
MineralGroups[keyion(s) orelement(s)] Carbonates(CO32*)
Halides(CIT,F‘,Br")
Oxides(O2-)
Sulfides(SZT)
Sulfates(SO.,2_)
Nativeelements(singleelements)
MineralName Calcite Dolomite Halite Fluorite(Fluorspar) Sylvite Hematite Magnetite Corundum Ice Galena Sphalerite Pyrite Chalcopyrite Cinnabar Gypsum Anhydrite Barite Gold Copper Diamond Sulfur Graphite Silver Platinum
ChemicalFormula CaCO CaM9(CO3) NaCl CaF KCI Fe2O Fe3O A H PbS ZnS F CuFeS HgS n ___ CaSO4-2H2O CaSO BaSO Au Cu C S C Ac Pt
EconomicUse Portlandcement,lime Portlandcement,lime Commonsalt Hydrofluoricacidproduction,steelmaking Fertilizer Oreofiron,pigment Oreofiron Gemstone,abrasive Solidformofwater Oreoflead Oreofzinc Sulfuricacidproduction Oreofcopper Oreofmercury Plaster Plaster Drillingmud Trade,jewelry Electricalconductor Gemstone,abrasive Sulfadrugs,chemicals Pencillead,drylubricant Jewelry,photography Catalyst
g MineralGroups 43
“IGIJRE2(salt)atanundergroundminein GrandSaline,Texas.(PhotobyTomBochsler)
Students SometimesAsk...
Accordingtothetextbook,thickbedsofhaliteand gypsumformedwhenancientseasevaporated happenedintherecentpast? Yes 6 million years,theMediterraneanSea mayhavedriedupandthen refilledseveraltimes 65 percentofseawaterevaporates, themineralgypsumbeginsto precipitate,meaningitcomes outofsolutionandsettlesto thebottom 90 percent ofthewaterisgone,halite crystalsform,followedbysalts ofpotassiumandmagnesium. Deep-seadrillinginthe Mediterraneanhasencountered thickdepositsofgypsumand salt(mostlyhalite)sittingone atoptheothertoamaximum thicknessof 2 kilometers(1. miles).Thesedepositsare inferredtohaveresulted fromtectoniceventsthat
periodicallyclosedand reopenedtheconnection betweentheAtlanticOcean andtheMediterraneanSea (themodern-dayStraitsof Gibraltar)overthepastseveral millionyears whentheMediterraneanwas cutofffromtheAtlantic,the warmanddryclimateinthis regioncausedthe Mediterraneantonearly“dry up."Then,whentheconnection to theAtlanticwasopened,the Mediterraneanbasinwould refillwithseawaterofnormal salinity repeatedoverandoveragain, producingthelayersofgypsum andsaltfoundonthe Mediterraneanseafloor.
seasthathavelongsinceevaporated(trigirraass).Like limestone,bothareimportantnonmetallicresources. Haliteisthe mineralname for commontablesalt (NaCl).Gypsum(CaSO,,-2H2O),whichiscalciumsul- fatewithwaterboundintothestructure,isthemineral ofwhichplasterandothersimilarbuildingmaterialsare composed. Mostnonsilicatemineralclassescontainmembers thatareprizedfortheireconomicvalue theoxides,whosemembershematiteandmagnetiteare importantoresofiron(Figure Alsosignificantare thesulfides,whicharebasicallycompoundsofsulfur (S)andoneormoremetals- fidemineralsincludegalena(lead),sphalerite(zinc), andchalcopyrite(copper).Inaddition,nativeelements, includinggold,silver,andcarbon(diamonds),plusa hostofothernonsilicateminerals—fluorite(fluxinmak- ingsteel),corundum(gemstone,abrasive),andurani- nite(auraniumsource)—areimportanteconomically (seeBox2).
FIGURE Magnetite(A)andhematite(B)arebothoxidesandare bothimportantoresofiron.(PhotosbyE) -
A a
Ha-
B
NaturalResources 45
CONCEPTcuscx 2. QListtheeightmostcommonelementsinEarth’scrustin orderofabundance(mosttoleast). QExplainthedifferencebetweenthetermssiliconandsilicate. QDrawasketchofthesilicon-oxygentetrahedron. QWhatisthemostabundantmineralinEarth’scrust? QListsixcommonnonsilicatemineralgroups(s) orelement(s)defineeachgroup? QWhatisthemostcommoncarbonatemineral? 0 Listeightcommonnonsilicatemineralsandtheireconomicuses.
Natural Resources
Earth’scrustandoceansarethesourceofawidevarietyofusefuland essentialmaterialsthathaveplayedacrucialroleinthedevelopment ofcivilization, yearsago,theuseofEarthmaterialshasexpandedresultinginmore complexsocieties,practicallyeverymanufacturedproduct containsmaterialsobtainedfromminerals themosteconomicallyimportantmineralgroups.
RenewableversusNonrenewable Resources Resourcesarecommonlydividedintotwobroadcategories. Someareclassifiedasrenewable,whichmeansthattheycan bereplenished overrelativelyshorttimespans. Common examplesareplantsandanimalsforfood,naturalfibersfor clothing,andforestproductsforlumberandpaper flowingwater,wind,andtheSunarealsoconsideredrenewable §£.frZ6). Bycontrast,manyotherbasicresourcesareclassifiedas nonrenewable,aluminum,and copperfallintothiscategory,asdoourmostimportantfuels:oil, naturalgas,andcoal- tinuetoform,theprocessesthatcreatethemaresoslowthatsig- nificantdepositstakemillionsofyearstoaccumulate, Earthcontainsfixedquantitiesofthesesubstances presentsuppliesareminedorpumpedfromtheground,there willbenomore,such asaluminum,canbeusedoverandoveragain,others,suchas oil,cannotberecycled.
l§’iiZi'iii'§‘i¥; Hydroelectricpowerisoneexampleofarenewableresource createdwhenGlenCanyonDamwasbuiltacrosstheColoradoRiver,itdrives turbinesandproduceselectricity.(PhotobyMichaelCollier)
46 CHAPTER2 MatterandMinerals
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_.-,;.'_
MineralResources Mineralresourcesarethoseoccurrencesofusefulmineralsthat areformedinsuchquantitiesthateventualextractionisreasonably certain presentlyextractedprofitably,aswellasknowndepositsthatare notyeteconomicallyortechnologicallyrecoverable. Anoreororedepositisanaturallyoccurringconcentrationof oneormoremetallicmineralsthatcanbeextractedeconomically (seeFigure2).Incommonusage,thetermoreisalsoappliedto somenonmetallicmineralssuchasfluoriteandsulfur, materialsusedforsuchpurposesasbuildingstone,roadaggre- gate,abrasives,ceramics,andfertilizersarenotusuallycalledores; rather,theyareclassifiedasindustrialrocksandminerals. Recallthatmorethan 98 percentofEarth’scrustiscomposed ofonlyeightelements,andexceptforoxygenandsilicon,allother elementsmakeuparelativelysmallfractionofcommoncrustal rocks(seeFigure2).Indeed,thenaturalconcentrationsofmany elementsareexceedinglysmall percentageofavaluableelementsuchasgoldhasnoeconomic
-:-
'ill*-_( 1;' \A <—s
»~
/I‘,
.-
value,becausethecostofextractingitgreatlyexceedsthevalueof
thegoldthatcouldberecovered.
Tohaveeconomicvalue,anelementmustbeconcentratedabove
thelevelofitsaveragecrustalabtmdance,coppermakes
upabout0
ascopperore,itmustcontainaconcentrationthatisabout 100 times
thisamotmt,ontheotherhand,represents8
ofthecrustandcanbeextractedprofitablywhenitisfoundincon-
centrationsonlyaboutfourtimesitsaveragecrustalpercentage.
Itisimportanttorealizethatadepositmaybecomeprofitable
toextractorloseitsprofitabilitybecauseofeconomicchanges
demandforametalincreasesandpricesrisesufficiently,thestatus
ofapreviouslyunprofitabledepositchanges,anditbecomesanore.
Thestatusofunprofitabledepositsmayalsochangeifatechnolog-
icaladvanceallowstheoretobeextractedatalowercostthanbefore.
Conversely,changingeconomicfactorscanturnaonceprof-
itableoredepositintoanunprofitabledepositthatcannolonger
becalledanore-
ingoperationlocatedatBinghamCanyon,Utah,oneofthelargest
open-pitminesonEarth(i.>it,§.i_iLi.‘£‘.;;e:.;;ri).Miningwashaltedthere
J‘“ --‘==Z..;'s-"~__,.1, ,"7Q.". -. ,.-
AerialviewofBinghamCanyoncopperminenearSaltLakeCity,Utah, thehugevolumeofmaterialremovedandprocessedeachday(about200,000tons)yieldsenoughmetaltobeprofitable.(PhotobyMichaelCollier)
Chapter 02
Course: Secondary education (bio sci)
University: Eastern Visayas State University
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