Lecture#2 Minerals.pdf Engineering Geology

Geology Engineering.. Minerals

1. Department of Civil Engineering
University of Engineering & Technology Peshawar
CE-217
ENGINEERING GEOLOGY & SEISMOLOGY
(03 Credit Hours)
Instructor:
Engr. Muhammad AdeelArshad
LECTURE-02

2. 1.What are Minerals?
2.What are different groups of Minerals?
3.How do we Identify minerals?
4.Examples of Common Rock Forming Minerals
Outlines of the Presentation
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Engg. Geology & Seismology (CE-217)
Instructor: Engr. Muhammad Adeel Arshad

3. What are Minerals?
➢Amineralisanaturallyoccurringsolidchemicalsubstanceandisstableat
roomtemperature,representablebyachemicalformula,formedthrough
geologicalprocesses,usuallyabiogenic(notproducedbylivingorganisms),
andhasanorderedatomicstructure.
➢Itisdifferentfromarock,whichcanbeanaggregateofmineralsornon-
minerals,anddoesnothaveaspecificchemicalcomposition.
➢Thestudyofmineralsiscalledmineralogy.
➢Asthebasicconstituentofrock,mineralscontrolmuchofrockbehavior.
Somemineralsareverystrongandresistanttodeteriorationandproduce
rockwithsimilarproperties,whileothersaremuchsofterandproduce
weakerrock.
➢Thesilicatemineralscomposeover90%oftheEarth’scrust.Siliconand
oxygenconstituteapproximately75%oftheEarth'scrust,whichtranslates
directlyintothepredominanceofsilicateminerals.
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Engg. Geology & Seismology (CE-217)
Instructor: Engr. Muhammad Adeel Arshad

4. What are Minerals?
ThreeConditionsmustbesatisfiedforasubstancetobeamineral:
➢Itmustbeacrystallinesolid:Infact,mostsolidsarecrystalline.Acrystallinesubstance
isoneinwhichtheatomsarearrangedina3-dimensional,regularrepeating,orderly
pattern.Liquidsarenotcrystallinebecausetheiratomsormoleculesarefreetomove
about.Mineral’sparticularcrystalstructurecanhaveapronouncedinfluenceonthe
mineral’sproperties.Diamondandgraphitehaveanidenticalchemicalcomposition
[polymorphs:sameformula,differentforms].DiamondisthehardestsubstanceonEarth
andgraphite,thesoftest.Thishappensbecausethecarbonatomsingraphiteare
arrangedintosheetswhichcanslideeasilypasteachother,whilethecarbonatomsin
diamondformastrong,interlockingthree-dimensionalnetwork.
➢Itmusthaveformedthroughgeologicprocesses:Human-made,crystalline
substancearenotregardedasminerals.Mostmineralsareinorganic,butsomeare
organic(likecalciteincoralsecretedbyorganisms).
➢Itmusthaveaspecificchemicalcomposition:chemicalanalysisofanysampleofa
givenmineralwillalwaysproducethesameratiosofelementsi.e.thecompositionofany
mineralcanbeexpressedasachemicalformula.
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Engg. Geology & Seismology (CE-217)
Instructor: Engr. Muhammad Adeel Arshad

5. Ore Forming Minerals
Mineralsmaybedividedintotwogroups:
Ore-formingminerals
➢AnOREisatypeofrockthat
containsmineralswithimportant
elementsincludingmetals.The
oresareextractedthroughmining;
thesearethenrefinedtoextractthe
valuableelement(s)
➢Oftheseveralthousand(~5000)
identifiablemineralsonearth,only
afewhundredareclassifiedas
rock-formingminerals.
IronOre
GoldOre
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Engg. Geology & Seismology (CE-217)
Instructor: Engr. Muhammad Adeel Arshad

6. Rock Forming Minerals
Thesemakeupmorethan90%oftheEarth’scrust.
SilicateGroupofMinerals:
▪Feldspargroup
▪Pyroxenegroup
▪Amphibolegroup
▪Quartz
▪Micagroup
Non-SilicateGroupofMinerals:
▪Calcite
▪Diorite
❑Themostcommonmineralsarefeldsparandquartz.Theyare
encounteredinbeachsandandthemostcommonrocks.
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Engg. Geology & Seismology (CE-217)
Instructor: Engr. Muhammad Adeel Arshad

7. Common Rock Forming Minerals
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Engg. Geology & Seismology (CE-217)
Instructor: Engr. Muhammad Adeel Arshad

8. Minerals Identification
➢Mineralsaredistinguishedbyvariouschemicalandphysicalproperties.
➢Classifyingmineralscanrangefromsimpletoverydifficult.Amineralcan
beidentifiedbyseveralphysicalproperties,someofthembeingsufficient
forfullidentificationwithoutequivocation.
➢Inothercases,mineralscanonlybeclassifiedbymorecomplex
chemicalorX-raydiffractionanalysis;thesemethods,however,canbe
costlyandtime-consuming.
➢Someofthephysicalpropertiesofmineralswhichmaybedetermined
withoutelaborateequipmentincludecolor,streak,luster,hardness,
crystalshape,cleavage,fracture,density,taste,smellandmagnetism.
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Engg. Geology & Seismology (CE-217)
Instructor: Engr. Muhammad Adeel Arshad

9. Minerals Identification
Color
➢Somemineralshavecharacteristiccolordueto
compositionofthemineralsandthe
arrangementoftheconstituentatoms:for
exampleblackcolorofmagnetite,greenof
chloriteandbrassyyellowofpyrite
➢Mineralslikequartzandcalcitehavevariable
colorwhenseenindifferentdirections.Thisis
called“playofcolor”.
➢Colorisextremelyvariableinquartzandmanyothermineralsbecause
evenminutechemicalimpuritiescanstronglyinfluenceit.Specimenof
Quartzcrystalsmaybewhite,pink,black,yellow,orpurple.
➢Colorcan’tbethesoleidentificationproperty
9
Engg. Geology & Seismology (CE-217)
Instructor: Engr. Muhammad Adeel Arshad

10. Minerals Identification
Luster
➢Howshinnythemineralis.Thequalityand
intensityoflightthatreflectsfromamineral
▪Metallic–shineslikeapolishedmetal
▪Vitreous–shineslikeglass
▪Pearly–shineslikeapearl
▪Resinous–shineslikethesurfacewas
coveredbyoilorgrease.
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Engg. Geology & Seismology (CE-217)
Instructor: Engr. Muhammad Adeel Arshad
Non-metallic mineral
Metallic mineral

11. Minerals Identification
Streak
➢Colorofmineralinpowder(pulverized)formiscalledstreak
➢Powderisobtainedbycrushingthemineral.Orthemineralsmaybe
rubbedagainstunglazedporcelainstreakplatetoobtainthestreak.
➢Colorofthestreakdiffersfromcolorofmineral:forexamplethecolorof
pyriteisbrassyellowanditsstreakisdarkgreen.Hematite,oftenagray
tosilver-graymineralhasared-brownstreak
11
Engg. Geology & Seismology (CE-217)
Instructor: Engr. Muhammad Adeel Arshad

12. Minerals Identification
➢Itisoneofthemostusefuldiagnostic
toolsbecauseitisidenticalforagiven
mineralfromonesampletoanother.
➢Mineralsbreakwitheaseproducing
smoothsurfacesiscalledperfect
cleavage.Itcanbeeithergood,distinct,
indistinctandimperfect.
➢Somemineralssuchasmicahaveperfect
cleavageinonedirection.Thefeldspars,
hastwocleavages.Saltbreaksinto
cubes,withcleavagein3directions,allat
90degrees.Quartzhasnocleavage.
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Engg. Geology & Seismology (CE-217)
Instructor: Engr. Muhammad Adeel Arshad
Cleavage
➢Thecleavageofthemineralsisitscapacitytosplitmorereadilyincertain
directionsthaninothers,duetothearrangementoftheatoms.

13. Minerals Identification
Fracture
➢Thenatureofabrokensurfaceofamineral
isknownasfracture,butthebreaking
shouldbeinanyotherdirectionthanthe
cleavage.
➢Mineralsthathavenocleavagecommonly
haveanirregularfracture.
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Engg. Geology & Seismology (CE-217)
Instructor: Engr. Muhammad Adeel Arshad
Conchoidal Fracture in Quartz
Irregular Fracture in Quartz

14. Minerals Identification
Hardness
➢Thehardnessofamineral,ascommonlydeterminedonfreshmaterial,is
measuredbyitsabilitytoresistscratching.
➢GeologistsrankmineralsaccordingtohardnessusingtheMoh'sscale.In
sequenceofincreasinghardnessfrom1to10,thefollowingmineralsare
usedasstandardofcomparison:
▪Talc=1
▪Gypsum=2
▪Calcite=3
▪Fluorite=4
▪Apatite=5
▪Feldspar=6
▪Quartz=7
▪Topaz=8
▪Diamond=10
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Engg. Geology & Seismology (CE-217)
Instructor: Engr. Muhammad Adeel Arshad
scratched by a finger nail
scratched by a knife
scarcely scratched by a knife
not scratched by a knife

15. Minerals Identification
SpecificGravity
➢SpecificGravitymeanstheweightofasubstancecomparedwiththe
weightofanequalvolumeofwater.Thespecificgravityofquartzis2.65.
Somemineralsareheavierthantheothers.Thespecificgravityofmajority
mineralsrangefrom2.55to3.2.
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Engg. Geology & Seismology (CE-217)
Instructor: Engr. Muhammad Adeel Arshad

16. Minerals Identification
CrystalForm
➢Internalatomicarrangementindefinitegeometricpatternsissometimes
outwardlyexpressedincrystalform.
➢Mineralsdonotalwaysabletodeveloptheircharacteristiccrystalfaces.
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Engg. Geology & Seismology (CE-217)
Instructor: Engr. Muhammad Adeel Arshad

17. Minerals Identification
Magnetism
➢Afewmineralsareattractedbyamagnet.
Oftheseminerals,magnetite(Fe
3O
4)and
pyrrhotite(areddish-bronzemineral
consistingofironsulphide)arethemost
commonexamples.
ReactiontoDiluteHydrochloricAcid
➢Carbonateminerals,especiallycalcite,may
beidentifiedbytheirreactionwithdilute
HCl.Thisreactionisintheformofrapid
bubbling,oreffervescence,ascarbon
dioxideisreleased.Non-carbonate
mineralsdonotreacttoHCl.
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Engg. Geology & Seismology (CE-217)
Instructor: Engr. Muhammad Adeel Arshad
Pyrrhotite
Calcite Minerals

18. Examples of Common Rock Forming Minerals
Feldspars
➢Feldsparisthemostabundantmineralandmakeupasmuchas51%of
theEarth'scrust.
➢Feldsparscrystallizefrommagma inbothintrusiveandextrusive
igneousrocks,asveins,andarealsopresentinmanytypesof
metamorphicrockandinmanytypesofsedimentaryrock.
➢Feldsparshavemoderatehardness.
➢Therearetwotypes.
✓Orthoclasefeldsparscontainpotassium(KaAlSi3O8)andusuallyrange
fromwhitetopink.
✓Plagioclasefeldsparscontainsodium(NaAlSi3O8),calcium
(CaAl2Si2O8)orboth,andrangefromwhitetograytoblack.
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Engg. Geology & Seismology (CE-217)
Instructor: Engr. Muhammad Adeel Arshad

19. Examples of Common Rock Forming Minerals
Quartz
➢Secondmostabundantmineralintheearth’scrust.
➢Therearemanydifferentvarietiesofquartz,severalofwhicharesemi-precious
gemstones.
➢Itisalsoverycommoningredientinmanykindsofrock.
➢Itissilicate(SiO2),andusuallyhasatranslucenttomilkywhitecolor.
➢Thelusterisvitreous.
➢Quartzisharderthanmostminerals(hardness7),andthusisveryresistantto
weathering.
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Engg. Geology & Seismology (CE-217)
Instructor: Engr. Muhammad Adeel Arshad

20. Examples of Common Rock Forming Minerals
Mica
➢Translucent(semi-transparent)thinsheetsorflakes.
➢Therearetwocommonvarieties.
✓Muscoviteispotassiumaluminumsilicateofcolorless
orsilverytint,pearlylusterandespeciallyonevery
perfectcleavage.
✓Biotite,theothercommonvariety,isacomplexsilicate
ofpotassium,magnesiumandironandaluminum.
➢Biotiteandmuscovitearesimilarinphysicalproperties.
Botharesoft,2.5-3,withoneperfectcleavage.
➢Thesheetsofmicahaveverylowcoefficientoffriction,
whichcanproduceshearfailureincertainrocks,suchas
schist(pronouncedasshist).
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Engg. Geology & Seismology (CE-217)
Instructor: Engr. Muhammad Adeel Arshad
Muscovite Flakes
BiotiteFlakes

21. Examples of Common Rock Forming Minerals
Calcite
➢Amineralmadeofcalciumcarbonate
(CaCO3).
➢Usuallywhite,pinkorgray.
➢Solubleinwater,andthuscanbe
transportedbygroundwaterintocracksin
rockwhereitprecipitateoutofsolution.
➢Precipitateinsoil,becomingacementing
agent.
➢muchsofterthenquartzorfeldspar.
Hardnessis3.
➢Havevigorousreactiontohydrochloricacid.
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Engg. Geology & Seismology (CE-217)
Instructor: Engr. Muhammad Adeel Arshad
Calcite Minerals

22. Examples of Common Rock Forming Minerals
Dolomite
➢Similartocalcitewithmagnesiumadded.
➢Lessvigorousreactiontodilutehydrochloricacid.
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Engg. Geology & Seismology (CE-217)
Instructor: Engr. Muhammad Adeel Arshad
Dolomite

23. The End
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Engg. Geology & Seismology (CE-217)
Instructor: Engr. Muhammad Adeel Arshad