Chapter3 minerals-110708161714-phpapp01

Essentials of GeologyEssentials of Geology
33rdrd
EditionEdition
Chapter 3
Norton Media LibraryNorton Media Library

Patterns in Nature: Minerals
Prepared by:Prepared by:
Ronald ParkerRonald Parker,, Senior GeologistSenior Geologist
Fronterra GeosciencesFronterra Geosciences
Houston, Oklahoma City, Denver, Anchorage, Dallas, Midland, Aberdeen, Vienna, Buenos Aires, NeuquénHouston, Oklahoma City, Denver, Anchorage, Dallas, Midland, Aberdeen, Vienna, Buenos Aires, Neuquén
www.fronterrageo.comwww.fronterrageo.com

Essentials of Geology, 3rd
edition, by Stephen Marshak Chapter 3: Patterns in Nature: Minerals
MineralsMinerals
 Minerals are the “building blocks” of rocks—hence,Minerals are the “building blocks” of rocks—hence,
Earth.Earth.
 More than 4,000 are known.More than 4,000 are known.
 Dozens of new minerals are discovered annually.Dozens of new minerals are discovered annually.
 Human interest in minerals spans millenia.Human interest in minerals spans millenia.

MineralsMinerals
 Developed societies depend on mineral resources.Developed societies depend on mineral resources.
 Metals – Iron, copper, lead, zinc, nickel, aluminum, etc.Metals – Iron, copper, lead, zinc, nickel, aluminum, etc.
 Non-metals – Gypsum, limestone, aggregate, clay.Non-metals – Gypsum, limestone, aggregate, clay.

MineralsMinerals
Figure 3.2b
Figure 3.1
Figure 3.2a
 Economically important – Drive world economies.Economically important – Drive world economies.
 Historically important – Dictated human history.Historically important – Dictated human history.
 Iron.Iron.
 Copper.Copper.
 Gold.Gold.
 Diamonds.Diamonds.
 Gems.Gems.

Mineral DefinitionMineral Definition
 Geologic definition of a mineral is specialized:Geologic definition of a mineral is specialized:
 Naturally occurring.Naturally occurring.
 Solid.Solid.
 Definite chemicalDefinite chemical
composition.composition.
 Ordered atomicOrdered atomic
arrangement.arrangement.
 Mostly inorganic.Mostly inorganic.
 A mineraloid exhibits some of these properties.A mineraloid exhibits some of these properties.
 Doesn’t include “minerals” in the nutritional sense.Doesn’t include “minerals” in the nutritional sense.

RocksRocks
 Rocks are earth materials made from minerals.Rocks are earth materials made from minerals.
 Most rocks contain more than one kind of mineral.Most rocks contain more than one kind of mineral.
 Example: GraniteExample: Granite
K-feldspar – Pink.K-feldspar – Pink.
Quartz – Gray.Quartz – Gray.
Hornblende – Black.Hornblende – Black.
 Some are monomineralic.Some are monomineralic.
 Limestone (Calcite)Limestone (Calcite)
 Rock salt (Halite)Rock salt (Halite)
 Glacial ice.Glacial ice.

Crystalline StructureCrystalline Structure
 Atoms in a mineral are specifically ordered.Atoms in a mineral are specifically ordered.
 A solid with disordered atoms is called a glass.A solid with disordered atoms is called a glass.
 Crystalline structure is based on atomic patterns.Crystalline structure is based on atomic patterns.

CrystalsCrystals
 Rare minerals displaying flat external faces.Rare minerals displaying flat external faces.
 Crystal faces form best in open cavities.Crystal faces form best in open cavities.
 Crystals are often prized mineral specimens.Crystals are often prized mineral specimens.

CrystalsCrystals
 Constancy of interfacial angles.Constancy of interfacial angles.
 Different samples of the same mineral will have the sameDifferent samples of the same mineral will have the same
crystal faces.crystal faces.
 Adjacent faces are alwaysAdjacent faces are always
oriented at the same angle.oriented at the same angle.
 Crystal faces reflect theCrystal faces reflect the
internal atomic order.internal atomic order.

Crystal LatticeCrystal Lattice
 Ordered atoms in crystals form a 3-D lattice.Ordered atoms in crystals form a 3-D lattice.
 Lattices are patterns that repeat in three dimensions.Lattices are patterns that repeat in three dimensions.
 This internal pattern controls most mineral properties.This internal pattern controls most mineral properties.
 Crystal shape.Crystal shape.
 Symmetry.Symmetry.

Atomic BondingAtomic Bonding
 Lattice atoms are held in place by atomic bonds.Lattice atoms are held in place by atomic bonds.
 Bond characteristics also govern mineral properties.Bond characteristics also govern mineral properties.
 Models depict atoms, bonds, and lattices.Models depict atoms, bonds, and lattices.

Graphite
PolymorphsPolymorphs
Diamond
 Minerals with the same composition; different structure.Minerals with the same composition; different structure.
 Polymorphs reveal the importance of bond type.Polymorphs reveal the importance of bond type.
 Diamond and graphite are carbon polymorphs (C).Diamond and graphite are carbon polymorphs (C).
 Diamond – Strong covalent bonds; hardest mineral.Diamond – Strong covalent bonds; hardest mineral.
 Graphite – Weak van der Waals bonds; softest mineral.Graphite – Weak van der Waals bonds; softest mineral.

Crystal GrowthCrystal Growth
 Crystals grow as atoms attach to mineral surfaces.Crystals grow as atoms attach to mineral surfaces.
 Growth starts from a central seed crystal.Growth starts from a central seed crystal.
 Growth expands outward as atoms accumulate.Growth expands outward as atoms accumulate.

Crystal GrowthCrystal Growth
 Outward crystal growth fills available space.Outward crystal growth fills available space.
 Resulting crystal shape is governed by surroundings.Resulting crystal shape is governed by surroundings.
 Open space – Good crystal faces grow.Open space – Good crystal faces grow.
 Confined space – No crystal faces.Confined space – No crystal faces.
 Crystals grow by…Crystals grow by…
 Solidification from a melt.Solidification from a melt.
 Precipitation from solution.Precipitation from solution.
 Solid-state diffusion.Solid-state diffusion.

Mineral Physical PropertiesMineral Physical Properties
Pyrite
 Characteristics determined by your five senses.Characteristics determined by your five senses.
 Used to ID minerals.Used to ID minerals.
 Properties depend upon…Properties depend upon…
 Chemical composition.Chemical composition.
 Crystal structure.Crystal structure.
 Some are diagnostic.Some are diagnostic.
Example: Pyrite (FeSExample: Pyrite (FeS22))
Cubic crystals, high specific gravity, striated crystal faces, blackCubic crystals, high specific gravity, striated crystal faces, black
streak, metallic luster, dull brassy color, sulfur smell when crushed,streak, metallic luster, dull brassy color, sulfur smell when crushed,
erroneously mistaken for gold (fool’s gold).erroneously mistaken for gold (fool’s gold).
 Minerals have unique sets of physical properties.Minerals have unique sets of physical properties.

Needle-like crystal habit
 Common properties ofCommon properties of
minerals are...minerals are...
 Crystal form.Crystal form.
 Crystal habit.Crystal habit.
 Luster.Luster.
 Color.Color.
 Streak.Streak.
 Hardness.Hardness.
 Cleavage.Cleavage.
 Fracture.Fracture.
 Specific gravity.Specific gravity.

Calcite effervesces with acid
Magnetite crystals on a large magnet.
 Less common physical properties are...Less common physical properties are...
 Taste.Taste.
 Smell.Smell.
 Feel.Feel.
 Elasticity.Elasticity.
 Magnetism.Magnetism.
 Effervescence.Effervescence.
 Diaphaneity.Diaphaneity.
 Piezoelectricity.Piezoelectricity.
 Pyroelectricity.Pyroelectricity.
 Refractive index.Refractive index.
 Malleability.Malleability.
 Ductility.Ductility.
 Sectility.Sectility.

ColorColor
Quartz – Many colors Malachite – Always green
 Color is diagnostic for some minerals.Color is diagnostic for some minerals.
 Olivine is olive green.Olivine is olive green.
 Azurite is always blue.Azurite is always blue.
 Some minerals may exhibit a broad color range.Some minerals may exhibit a broad color range.
 Quartz (Clear, white, yellow, pink, purple, gray, etc).Quartz (Clear, white, yellow, pink, purple, gray, etc).
 Color varieties often reflect trace impurities.Color varieties often reflect trace impurities.

StreakStreak
Hematite – Red-brown streak
 Mineral color crushed on an unglazed porcelain plate.Mineral color crushed on an unglazed porcelain plate.
 Streak is often a useful diagnostic property.Streak is often a useful diagnostic property.
 Congruent streak – Streak color the same as the mineral.Congruent streak – Streak color the same as the mineral.
Magnetite – Black mineral; black streak.Magnetite – Black mineral; black streak.
 Incongruent streak – Streak color differs from the mineral.Incongruent streak – Streak color differs from the mineral.
Chromite – Black mineral; greenish-brown streak.Chromite – Black mineral; greenish-brown streak.

LusterLuster
Satin spar Gypsum – Satiny luster
Quartz – Vitreous luster
 The way a mineral surface scatters light.The way a mineral surface scatters light.
 Two subdivisions.Two subdivisions.
 Metallic – Looks like a metal.Metallic – Looks like a metal.
 Nonmetallic.Nonmetallic.
Vitreous (glassy).Vitreous (glassy).
Satiny.Satiny.
Silky.Silky.
Resinous.Resinous.
Pearly.Pearly.
Earthy (dull).Earthy (dull).
Adamantine (brilliant).Adamantine (brilliant).

 Scratching resistance of a mineral.Scratching resistance of a mineral.
 Hardness compared to the Mohs hardness scale.Hardness compared to the Mohs hardness scale.
 Talc, Graphite.Talc, Graphite.
 Gypsum.Gypsum.
 Calcite.Calcite.
 Fluorite.Fluorite.
 Apatite.Apatite.
 Orthoclase.Orthoclase.
 Quartz.Quartz.
 Topaz.Topaz.
 Corundum.Corundum.
 Diamond.Diamond.
HardnessHardness
Glass - Steel 5.5
Fingernail 2.5
Copper Penny 3.5
Steel File 6.5

Pyrite
Specific GravitySpecific Gravity
Potassium Feldspar
 Related to density (mass per volume)Related to density (mass per volume)
 Mineral weight over weight of equal water volume.Mineral weight over weight of equal water volume.
 Specific gravity is “heft”– How heavy it feels.Specific gravity is “heft”– How heavy it feels.
 Pyrite – Heavy (SG 5.0)Pyrite – Heavy (SG 5.0)
 Feldspar – Light (SG 2.6)Feldspar – Light (SG 2.6)
 Pyrite “feels” heavier than feldspar.Pyrite “feels” heavier than feldspar.

Crystal HabitCrystal Habit
Cubes Hexagonal PrismsBlades
RhombohedraDodecahedra
Octahedra
Tetragonal PrismsCompound Forms
 Crystal habit is the ideal shape of crystal faces.Crystal habit is the ideal shape of crystal faces.
 Ideal faces require ideal growth conditions.Ideal faces require ideal growth conditions.
 Many descriptive terms are used to characterize habit.Many descriptive terms are used to characterize habit.

Crystal FormCrystal Form
Amethyst Geode
 Minerals vary in crystal face development.Minerals vary in crystal face development.
 Euhedral – Good crystal faces; grown in open cavity.Euhedral – Good crystal faces; grown in open cavity.
 Anhedral – No crystal faces; grown in tight space.Anhedral – No crystal faces; grown in tight space.
 Subhedral – Between the two.Subhedral – Between the two.
 Face development indicates growth history.Face development indicates growth history.
 Anhedral crystals common; euhedral less so.Anhedral crystals common; euhedral less so.

CleavageCleavage
 Tendency to break along planes of lattice weakness.Tendency to break along planes of lattice weakness.
 Cleavage produces flat, shiny surfaces.Cleavage produces flat, shiny surfaces.
 Described by the number of planes and their angles.Described by the number of planes and their angles.
 Sometimes mistaken for crystal habit.Sometimes mistaken for crystal habit.
 Cleavage is through going; often forms parallel “steps”.Cleavage is through going; often forms parallel “steps”.
 Habit is only on external faces.Habit is only on external faces.
 1, 2, 3, 4, and 6 cleavages possible.1, 2, 3, 4, and 6 cleavages possible.

CleavageCleavage
Muscovite Mica
Amphibole
Potassium Feldspar
 Examples of Cleavage:Examples of Cleavage:
 1 direction1 direction
 2 directions at ~ 90º2 directions at ~ 90º
 2 directions NOT at 90º2 directions NOT at 90º

CleavageCleavage
Calcite
Halite
 Examples of Cleavage:Examples of Cleavage:
 Three directions at 90ºThree directions at 90º
 Three directions NOT at 90ºThree directions NOT at 90º

FractureFracture
Obsidian
 Some minerals lack planes of lattice weakness.Some minerals lack planes of lattice weakness.
 Due to equal molecular bonds in all directions.Due to equal molecular bonds in all directions.
 These minerals don’t cleave; they exhibit fracture.These minerals don’t cleave; they exhibit fracture.
 Example: Quartz displays conchoidal fracture.Example: Quartz displays conchoidal fracture.
Shaped like the inside of a clam shell.Shaped like the inside of a clam shell.
Breaks along smooth, curved surfaces.Breaks along smooth, curved surfaces.
Produces extremely sharp edges.Produces extremely sharp edges.

Mineral CompositionsMineral Compositions
74.3% of crustal minerals !!!74.3% of crustal minerals !!!
 Only about 50 minerals are abundant.Only about 50 minerals are abundant.
 98% of crustal mineral mass is from eight elements.98% of crustal mineral mass is from eight elements.
 OxygenOxygen OO 46.6%46.6%
 SiliconSilicon SiSi 27.7%27.7%
 AluminumAluminum AlAl 8.1%8.1%
 IronIron FeFe 5.0%5.0%
 CalciumCalcium CaCa 3.6%3.6%
 SodiumSodium NaNa 2.8%2.8%
 PotassiumPotassium KK 2.6%2.6%
 MagnesiumMagnesium MgMg 2.1%2.1%
 All othersAll others 1.5%1.5%

Mineral ClassesMineral Classes
Fluorite (Halide) Native CopperMalachite (Carbonate)
 Minerals are classified based upon the dominant anion.Minerals are classified based upon the dominant anion.
 SilicatesSilicates SiOSiO22
4-4-
Rock-forming mineralsRock-forming minerals
 OxidesOxides OO2-2-
Magnetite, HematiteMagnetite, Hematite
 SulfidesSulfides SS--
Pyrite, GalenaPyrite, Galena
 SulfatesSulfates SOSO44
2-2-
GypsumGypsum
 HalidesHalides ClCl--
or For F--
Fluorite, HaliteFluorite, Halite
 CarbonatesCarbonates COCO33
2-2-
Calcite, DolomiteCalcite, Dolomite
 Native elementsNative elements Cu, Au, CCu, Au, C Copper, Gold, GraphiteCopper, Gold, Graphite

Silicate MineralsSilicate Minerals
 Silicates are know as “the rock-forming minerals.”Silicates are know as “the rock-forming minerals.”
 They dominate Earth’s crust.They dominate Earth’s crust.
 Oxygen and silicon…Oxygen and silicon…
Make up 94.7% of crustal volume, and...Make up 94.7% of crustal volume, and...
74.3% of crustal mass.74.3% of crustal mass.

 The anionic unit is the silica tetrahedron.The anionic unit is the silica tetrahedron.
 4 oxygen atoms are bonded to 1 silicon atom (SiO4 oxygen atoms are bonded to 1 silicon atom (SiO44
4-4-
).).
 Silicon is tiny; oxygen is huge.Silicon is tiny; oxygen is huge.
 The silica tetrahedron has a net -4 ionic charge.The silica tetrahedron has a net -4 ionic charge.
 The silicate unit can be depicted by…The silicate unit can be depicted by…
Spheres.Spheres.
A ball-and-stick model.A ball-and-stick model.
Polyhedra.Polyhedra.

Type of Silicate Structure Formula Si:O Ratio
Independent TetrahedraIndependent Tetrahedra SiOSiO44 0.250.25
Double TetrahedraDouble Tetrahedra SiSi22OO77 0.290.29
Ring SilicatesRing Silicates SiSi66OO1818 0.330.33
Single ChainsSingle Chains SiOSiO33 0.330.33
Double ChainsDouble Chains SiSi44OO1111 0.360.36
Sheet SilicatesSheet Silicates SiSi22OO55 0.400.40
Framework SilicatesFramework Silicates SiOSiO22 0.500.50
 Silica tetrahedra link together by sharing oxygens.Silica tetrahedra link together by sharing oxygens.
 More shared oxygen = lower Si:O ratio; governs…More shared oxygen = lower Si:O ratio; governs…
 Melting temperature.Melting temperature.
 Mineral structure and cations present.Mineral structure and cations present.
 Susceptibility to chemical weathering.Susceptibility to chemical weathering.

Independent TetrahedraIndependent Tetrahedra
KyaniteGarnet
 Tetrahedra share no oxygens–they are linked by cations.Tetrahedra share no oxygens–they are linked by cations.
 Olivine group.Olivine group.
High-temperature Fe-Mg silicate.High-temperature Fe-Mg silicate.
Small green crystals; no cleavage.Small green crystals; no cleavage.
 Garnet group.Garnet group.
Equant crystals with no cleavage.Equant crystals with no cleavage.
Dodecahedral (12-sided) crystals.Dodecahedral (12-sided) crystals.

Single-Chain SilicatesSingle-Chain Silicates
Pyroxene
 Single-chain structures bonded with Fe and Mg.Single-chain structures bonded with Fe and Mg.
 Pyroxene Group.Pyroxene Group.
Black-to-green color.Black-to-green color.
Two distinctive cleavages at nearly 90°.Two distinctive cleavages at nearly 90°.
Stubby crystals.Stubby crystals.
Augite is the most common pyroxene.Augite is the most common pyroxene.

Double-Chain SilicatesDouble-Chain Silicates
Hornblende
 Double chain of silica tetrahedra bonded together.Double chain of silica tetrahedra bonded together.
 Contain a variety of cations.Contain a variety of cations.
 Amphibole group - two perfect cleavages;Amphibole group - two perfect cleavages;
elongate crystals.elongate crystals.

Sheet SilicatesSheet Silicates
Muscovite Mica
 Two dimensional sheets of linked tetrahedra.Two dimensional sheets of linked tetrahedra.
 Characterized by one direction of perfect cleavage.Characterized by one direction of perfect cleavage.
 Mica group – Biotite (dark) and Mucsovite (light).Mica group – Biotite (dark) and Mucsovite (light).
 Clay mineral group – Feldspar-weathering residue; tiny.Clay mineral group – Feldspar-weathering residue; tiny.

Framework SilicatesFramework Silicates
Potassium Feldspar
 All four oxygens in the silica tetrahedra are shared.All four oxygens in the silica tetrahedra are shared.
 Feldspar group – Plagioclase and potassium feldspar.Feldspar group – Plagioclase and potassium feldspar.
 Silica (Quartz) group – Contains only Si and O.Silica (Quartz) group – Contains only Si and O.

GemsGems
Watermelon Tourmaline
Aquamarine Beryl
 Minerals with special value.Minerals with special value.
 Rarity.Rarity.
 Beauty.Beauty.
Color.Color.
Interaction with light.Interaction with light.
Dispersion.Dispersion.
High refractive index.High refractive index.

GemsGems
 Gems are cut and polished to be used in jewelry.Gems are cut and polished to be used in jewelry.
 Facets are ground onto a gemstone by a machine.Facets are ground onto a gemstone by a machine.
 Facets are not natural crystal faces.Facets are not natural crystal faces.

DiamondsDiamonds
 Diamonds originate under extremely high pressure.Diamonds originate under extremely high pressure.
 ~ 150 km deep (upper mantle).~ 150 km deep (upper mantle).
 Pure carbon is compressed into the diamond structure.Pure carbon is compressed into the diamond structure.
 Rifting causes deep mantle rock to move upward.Rifting causes deep mantle rock to move upward.
 Diamonds are found in kimberlite pipes.Diamonds are found in kimberlite pipes.

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Independent and Employee-OwnedIndependent and Employee-Owned
This concludes the Norton Media LibraryThis concludes the Norton Media Library
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Essentials of GeologyEssentials of Geology
33rdrd
Edition (2009)Edition (2009)
by Stephen Marshakby Stephen Marshak

Chapter3 minerals-110708161714-phpapp01

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