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Lab #4:Lab #4:

Minerals: Building Minerals: Building

Blocks of RocksBlocks of Rocks

Minerals: Building Blocks Minerals: Building Blocks

of Rocksof Rocks

By definition a By definition a mineralmineral is/hasis/has

Naturally occurringNaturally occurring

Inorganic solidInorganic solid

Ordered internal molecular structureOrdered internal molecular structure

Definite chemical compositionDefinite chemical composition

RockRock

A solid aggregate of mineralsA solid aggregate of minerals

Composition and Structure Composition and Structure

of Mineralsof Minerals

ElementsElements

Basic building blocks of mineralsBasic building blocks of minerals

Over 100 are known (92 naturally Over 100 are known (92 naturally

occurring)occurring)

AtomsAtoms

Smallest particles of matterSmallest particles of matter

Retain all the characteristics of an Retain all the characteristics of an

elementelement

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Composition and Structure Composition and Structure

of Mineralsof Minerals

Atomic structureAtomic structure

Central region called the Central region called the nucleusnucleus

�� Consists of Consists of protonsprotons (+ charges) and (+ charges) and

neutronsneutrons ((-- charges)charges)

ElectronsElectrons

�� Negatively charged particles that surround Negatively charged particles that surround

the nucleusthe nucleus

�� Located in discrete energy levels called Located in discrete energy levels called

shellsshells

Structure of an AtomStructure of an Atom

Figure 1.5 A

Composition and Structure of Composition and Structure of

MineralsMinerals

Chemical bondingChemical bonding

Formation of a compound by Formation of a compound by

combining two or more elementscombining two or more elements

Atoms gain or lose outermost Atoms gain or lose outermost

electrons to form electrons to form ionsions

Oppositely charged ions attract one Oppositely charged ions attract one

another to produce a neutral another to produce a neutral

chemical compoundchemical compound

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Composition and Structure of Composition and Structure of

MineralsMinerals

Isotopes and radioactive decayIsotopes and radioactive decay

Mass numberMass number = sum of neutrons + = sum of neutrons +

protons in an atomprotons in an atom

IsotopeIsotope = atom that exhibits variation = atom that exhibits variation

in its mass numberin its mass number

Unstable isotopes emit particles and Unstable isotopes emit particles and

energy in a process known as energy in a process known as

radioactive decayradioactive decay

Physical Properties Physical Properties

of Mineralsof Minerals

Crystal formCrystal form

External expression of a mineralExternal expression of a mineral’’s s

internal structureinternal structure

Often interrupted due to competition Often interrupted due to competition

for space and rapid loss of heatfor space and rapid loss of heat

A Garnet CrystalA Garnet Crystal

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Cubic Crystals of PyriteCubic Crystals of Pyrite

Figure 1.7 A

Physical Properties Physical Properties

of Mineralsof Minerals

LusterLuster

Appearance of a mineral in reflected Appearance of a mineral in reflected

lightlight

Two basic categoriesTwo basic categories

�� MetallicMetallic

�� NonmetallicNonmetallic

Other descriptive terms include Other descriptive terms include

vitreous, silky, or earthyvitreous, silky, or earthy

Galena (PbS) Displays Metallic Galena (PbS) Displays Metallic

LusterLuster

Figure 1.13

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Physical Properties Physical Properties

of Mineralsof Minerals

ColorColor

Generally unreliable for mineral Generally unreliable for mineral

identificationidentification

Often highly variable due to slight Often highly variable due to slight

changes in mineral chemistrychanges in mineral chemistry

Exotic colorations of certain minerals Exotic colorations of certain minerals

produce gemstonesproduce gemstones

Quartz (SiOQuartz (SiO22) Exhibits ) Exhibits

a Variety of Colorsa Variety of Colors

Physical Properties Physical Properties

of Mineralsof Minerals

StreakStreak

Color of a mineral in its powdered Color of a mineral in its powdered

formform

HardnessHardness

Resistance of a mineral to abrasion Resistance of a mineral to abrasion

or scratchingor scratching

All minerals are compared to a All minerals are compared to a

standard scale called the standard scale called the Mohs scale Mohs scale

of hardnessof hardness

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Streak Is Obtained on an Streak Is Obtained on an

Unglazed Porcelain PlateUnglazed Porcelain Plate

Figure 1.8

Mohs Scale

of

Hardness

Figure 1.9

Physical Properties Physical Properties

of Mineralsof Minerals

CleavageCleavage

Tendency to break along planes of Tendency to break along planes of

weak bondingweak bonding

Produces flat, shiny surfacesProduces flat, shiny surfaces

Described by resulting geometric Described by resulting geometric

shapesshapes

�� Number of planesNumber of planes

�� Angles between adjacent planesAngles between adjacent planes

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Fluorite, Halite, and Calcite All Fluorite, Halite, and Calcite All

Exhibit Perfect CleavageExhibit Perfect Cleavage

Figure 1.11

Physical Properties Physical Properties

of Mineralsof Minerals

FractureFracture

Absence of cleavage when a mineral Absence of cleavage when a mineral

is brokenis broken

Specific GravitySpecific Gravity

Weight of a mineral/weight of an Weight of a mineral/weight of an

equal volume of waterequal volume of water

Average value = 2.5 Average value = 2.5 –– 3.03.0

Conchoidal FractureConchoidal Fracture

Figure 1.12

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Physical Properties Physical Properties

of Mineralsof Minerals

Other propertiesOther properties

MagnetismMagnetism

Reaction to hydrochloric acidReaction to hydrochloric acid

MalleabilityMalleability

Double refractionDouble refraction

TasteTaste

SmellSmell

ElasticityElasticity

Mineral GroupsMineral Groups

Nearly 4000 minerals have been Nearly 4000 minerals have been namednamed

RockRock--forming mineralsforming minerals

Common minerals that make up most Common minerals that make up most of the rocks of Earthof the rocks of Earth’’s crusts crust

Only a few dozen membersOnly a few dozen members

Composed mainly of the 8 elements Composed mainly of the 8 elements that make up over 98% of the that make up over 98% of the continental crustcontinental crust

Elemental AbundancesElemental Abundances

in Continental Crustin Continental Crust

Figure 1.14

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Mineral GroupsMineral Groups

SilicatesSilicates

Most important mineral groupMost important mineral group

�� Comprise most rockComprise most rock--forming mineralsforming minerals

�� Very abundant due to large % of silicon Very abundant due to large % of silicon

and oxygen in Earthand oxygen in Earth’’s crusts crust

SiliconSilicon--oxygen tetrahedronoxygen tetrahedron

�� Fundamental building blockFundamental building block

�� Four oxygen ions surrounding a much Four oxygen ions surrounding a much

smaller silicon ion smaller silicon ion

Two

Illustrations

of the

Si–O

Tetrahedron

Figure 1.15

Mineral GroupsMineral Groups

Common silicate mineralsCommon silicate minerals

Feldspar groupFeldspar group

�� Most common mineral groupMost common mineral group

QuartzQuartz

�� Only common silicate composed entirely Only common silicate composed entirely

of oxygen and siliconof oxygen and silicon

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Potassium FeldsparPotassium Feldspar

Figure 1.17

Mineral GroupsMineral Groups

Important nonsilicate mineralsImportant nonsilicate minerals

Comprise only 8% of EarthComprise only 8% of Earth’’s crusts crust

Often occur as constituents in Often occur as constituents in

sedimentary rockssedimentary rocks

Table 1.1

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Mineral GroupsMineral Groups

Important nonsilicate mineralsImportant nonsilicate minerals

CarbonatesCarbonates

�� Primary constituents in limestone and Primary constituents in limestone and

marblemarble

�� Limestone is used commercially for Limestone is used commercially for

road paving, building stone, and as the road paving, building stone, and as the

main ingredient in Portland cementmain ingredient in Portland cement

Mineral GroupsMineral Groups

Important nonsilicate mineralsImportant nonsilicate minerals

HaliteHalite and and gypsumgypsum

�� Both are commonly found in thick layersBoth are commonly found in thick layers

�� Like limestone, both halite and gypsum Like limestone, both halite and gypsum

are important nonmetallic resourcesare important nonmetallic resources

Mineral GroupsMineral Groups

Important nonsilicate mineralsImportant nonsilicate minerals

A number of other minerals have A number of other minerals have

economic valueeconomic value

ExamplesExamples

�� HematiteHematite (oxide mined for iron ore)(oxide mined for iron ore)

�� SphaleriteSphalerite (sulfide mined for zinc ore)(sulfide mined for zinc ore)

�� GalenaGalena (lead)(lead)

�� Native copperNative copper (native element mined for (native element mined for

copper)copper)

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Native CopperNative Copper

Complete Lab #4:Complete Lab #4:

MineralsMinerals