◾ CHAPTER2:MI NERALSandROCKS Mi ner al smakeupt her ocksbeneat hy ourf eet ,t hesoi lt hatsuppor t spl ant s,andt hedeepr ock ofEar t h’ smant l e.Anyt hor oughst udyofEar t hmusti ncl udeanunder st andi ngofmi ner al s.Buti t i snotsuf f i ci entt ost udymi ner al si sol at edf r om t her estoft hepl anet .Rat herwecanl ear nmor e byobser v i ngt heway st hatmi ner al si nt er actwi t hot herEar t hsy st ems.Mi ner al sar esol i d subst ancest hatar epr esenti nnat ur eandcanbemadeofoneel ementormor eel ement s combi nedt oget her( chemi cal compounds) . Gol d,si l v erandcar bonar eel ement st hatf or m mi ner al sont hei rown.Theyar ecal l ednat i v e el ement s.I nst ead, or di nar yki t chensal ti sachemi cal compoundt hati scal l edr ocksal t , whi chi s ami ner alf or medofsodi um andchl or i nei ons.At oms,i onsandmol ecul est hatf or m ami ner al ar epr esenti nt hespacei nat i dywayandaccor di ngt owel l def i nedgeomet r i calshapes,whi ch ar ecal l edcr y st all at t i ces.Thest r uct ur eoft hecr y st all at t i cedef i nest heshapeoft hecr y st alas weseei t .Forexampl e, r ocksal torki t chensal ti sami ner alf or medofcubi cshapedcr y st al s.I t s cr y st all at t i cehast hesameshapeandconsi st sofsodi um andchl or i nei onst hatar epr esenti n t hespacei nal t er nat eor der . Whatar eMi ner al s? Mi ner al sar et hebui l di ngbl ocksofr ocks.Mi ner al ogi st suset hecr i t er i at odet er mi newhet hera mat er i al i scl assi f i edasami ner al ornot . ◾ Char act er i st i csofMi ner al s .Nat ur al l yoccur i ng-apr oductofEar t h’ snat ur al pr ocesses .I nor gani c-i tmustbepr oductofEar t h’ sphy si cal pr ocesses. .Homogeneoussol i d-mi ner al sshoul dhav edef i ni t ev ol umeandr i gi dshape .Def i ni t echemi cal composi t i on-r epr esent edbyachemi cal f or mul a .Or der l ycr y st al l i nest r uct ur e-at omsofmi ner al sar ear r angedi nanor der l yandr epeat i ng pat t er n ◾ Pr oper t i esofMi ner al s Toi dent i f ymi ner al s, mi ner al ogi st sobser v et hef ol l owi ngpr oper t i es: .Col or-mi ner al ’ scol ormaychangedependi ngont hesur f ace. .St r eak-col orofmi ner al i npowder edf or m. .Har dness-mi ner al sr esi st ancet oscr at chi ng .Cl eav age-mi ner al ’ sr esi st ancet obei ngbr okenandf r act ur e .Cr y st al l i nest r uct ur eorhabi t -t hechar act er i st i cext er nalshapeofani ndi v i dualcr y st alor cr y st al gr oup .Di aphanei t y / amountoft r anspar ency-abi l i t yt oal l owl i ghtt opasst hr oughi t .Thi si saf f ect ed bychemi cal makeupoft hemi ner al sampl e. .Lust er-howl i ghti sr ef l ect edof fasur f ace .Tenaci t y-descr i best hemi ner al sr eact i ont ost r ess. >Br i t t l eness-ami ner al t ur nsi nt opowder >Mal l eabi l i t y-ami ner al canbef l at t enedbypoundi ngwi t hahammer . >Duct i l i t y-ami ner al canbest r et chedi nt owi r e. >Fl exi bl ebuti nel ast i c-mi ner al sar ebentbutt heyr emai ni nt henewposi t i on. >Fl exi bl eandel ast i c-mi ner al sar ebent , andt heybr i ngbackt ot hei ror i gi nal posi t i on. >Sect i l i t y-abi l i t yofmi ner al st obesl i cedbyakni f e. ◾ ROCKS Pet r ol ogyi st hesci ent i f i cst udyofr ocks. Rocksar ecombi ned aggr egat i onofmi ner al s. Pet r ol ogi stcl assi f i edr ocksbasedonhowt heywer ef or med.I ngener al ,r ocksar ecl assi f i edas i gneous, sedi ment ar y , andmet amor phi cr ock. Ear t hi sasol i dr ockt oadept hof2, 900ki l omet er s, wher emant l emeet st hel i qui dout ercor e.A r ocki sanat ur al l yoccur r i ngsol i daggr egat eofoneormor emi ner al s.Theaggr egat emi ner al s f or mi ngt her ocksar ehel dt oget herbychemi calbonds.Gr ai nscanbedi f f er enti ncol or , t ext ur e, andsi zes.Geol ogi st st hengr oupr ocksi nt ot hr eecat egor i esbasedonhow t her ocksf or m: i gneous sedi ment ar y and met amor phi cr ock.Pet r ol ogy i st he sci ent i f i c st udy ofr ocks. Pet r ol ogi st scl assi f yr ocksbasedonhowt heywer ef or med. ◾ Thet y pesofRocks ▪I gneous-f or medf r om har deni ngandcr y st al l i z at i onofmagmaormol t enmat er i alt hat or i gi nat esdeepwi t hi nt heear t h. Twot y pesofi gneousr ock: .Ext r usi v e/ Vol cani cRock-f or mswhenmagmamakesi t swayt oEar t h’ ssur f aceasl av aand t hencool s.Thecr y st al sar ev er ysmal l ( f i negr ai ned)si ncet hecool i ngpr ocessi sf ast . .I nt r usi v e/ Pl ut oni c-I tcool ssl owl ybeneat ht heEar t hsur f aceandar ecr eat edbymagma.The i nt r usi v ei gneousr ockshav ev er yl ar gecr y st al s( coar segr ai ned) . I gneousr ocksar ecl assi f i edbasedon 1.Composi t i on FELSI C-l i ghti ncol or ; f el dsparandsi l i cat es MAFI C-dar ki ncol or ; madeupofmagnesi um andi r on I NTERMEDI ATE–bet weenmaf i candf el si c ULTRAMAFI C-v er ydar kcol or 2.Text ur e-ov er al l appear anceofr ock Aphani st i c-f i negr ai ned Phaner i t i c-coar segr ai ned Por phy r i t i c-l ar gecr y st al swi t hsmal l cr y st al s Gl assy-nonor der edsol i df r om r api dquenchi ng Py r ocl ast i c-composi t eofej ect edf r agment s Exampl es: Obsi di an, pumi ce, basal t , gr ani t e, di or i t e, gabbr o ▪Met amor phi c-f or msf r om pr eexi st i ngr ocks: ei t hermet amor phi c, i gneous, sedi ment ar y Exampl es: Quar t zi t e, mar bl e, sl at e, phy l l i t e Met amor phi sm -t r ansf or mat i onofoner ockt y pei nt oanot her . ▪Twot y pesofmet amor phi sm 1.Regi onal -duet ochangesi npr essur eandt emper at ur eov erl ar ger egi onoft hecr ust 2.Cont act-mai nl ybyheatduet ocont actwi t hmagma Met amor phi cRocksf or msf r om exi st i ngr ockt y pescal l ed“ par entr ock”i nt hepr ocesscal l ed met amor phi sm,whi chmeanschangei nf or m.Theor i gi nalr ockwhi chcanbeani gneous, sedi ment ar yoranot hermet amor phi cr ock i s subj ect ed t o heatand pr essur e,causi ng a pr of oundchemi cal orphy si cal change.Met amor phi cr ockscanbecl assi f i edi nt o: a.Text ur e-r ef er st ot hesi zear r angementadgr ai nswi t hi nt her ock. b.Fol i at i on-anypl anarar r angementofmi ner al gr ai nsorst r uct ur al f eat ur eswi t hi nt her ock. Fol i at ed-appear edbandedorl ay er ed,cont ai nscr y st al s.For medt hr oughpr essur eduet o compr essi onofr ockst hatcr eat ebandscal l edf ol i at i on.Exampl esar egnei ss,phy l l i t e,schi st , andsl at e. Nonf ol i at ed-madeupofonl yf ewmi ner al s.I thasnof ol i at i onorbands.Exampl esoft hi st y pe ar ehor nf el s, mar bl e, quar t zi t e, andnov acul i t e. ▪Sedi ment ar y-pr ov i dei nf or mat i onaboutsur f acecondi t i onst hatexi st edi nt heEar t h’ spast . Par t i cl es ofsand,shel l s,pebbl es,and ot herf r agment s ofmat er i al s cal l ed sedi ment s, accumul at ei nl ay er sandov erl ongper i odoft i mehar deni nt or ocks. Compact i onduet oi ncr easeofpr essur eofl ay er edsedi ment si tbi ndt oget hert of or mt he sedi ment ar yr ocks. ▪Thr eet y pesofsedi ment ar yr ocks a.Cl ast i cSedi ment ar yr ock-f or medf r om accumul at i onofcl ast s:l i t t l epi ecesofbr okenr ocks andshel l s. Exampl es: congl omer at e, br ecci a, sandst one, shal e b.Chemi cal -f or medwhendi ssol v edmi ner al spr eci pi t at ef r om asol ut i on. Exampl e: Hal i t e-f or medwhenabodyofseawat erbecomescl osedof fandev apor at es. c.Or gani c-r ocksf or medf r om t heaccumul at i onofani mal debr i s Exampl e: Coal -composedofor gani c mat t eri nt hef or m ofpl ant sf r agment s. TheRockCy cl e Whati st her ockcy cl e? Ther ockcy cl ei saconceptusedt oexpl ai nhowt het hr eebasi cr ockt y pesar er el at ed and how ear t hpr ocessesov ergeol ogi ct i me,changear ockf r om onet y pei nt o anot herpl at et ect oni cact i v i t y ,al ongwi t hweat her i ngander osi onalpr ocessesar e r esponsi bl ef ort hecont i nuedr ecy cl i ngofr ocks.
