earth lecture slide chapter five

Earth: Portrait of a Planet, 4th edition, by Stephen Marshak © 2011, W. W. Norton Earth: Portrait of a Planet, 4th edition, by Stephen Marshak © 2011, W. W. Norton Chapter 5: Patterns in Nature: MineralsChapter 5: Patterns in Nature: Minerals

Chapter 5Patterns in Nature: MineralsPatterns in Nature: Minerals


Patterns in Nature: MineralsPatterns in Nature: MineralsPatterns in Nature: MineralsPatterns in Nature: Minerals

Prepared by:Prepared by:

Ronald L. ParkerRonald L. Parker, , Senior GeologistSenior Geologist

Fronterra Geosciences,Fronterra Geosciences,

Denver, ColoradoDenver, Colorado


MineralsMinerals Minerals are interesting Earth materials that surround us.Minerals are interesting Earth materials that surround us. More than 4,000 minerals are known.More than 4,000 minerals are known. Around 50–100 new minerals are discovered annually.Around 50–100 new minerals are discovered annually. Human interest in minerals spans millennia. Human interest in minerals spans millennia.

A feathery ice crystal displays an ordered atomic structureA feathery ice crystal displays an ordered atomic structure


MineralsMinerals Minerals are divided into a few compositional classes.Minerals are divided into a few compositional classes. The most common class of minerals? The Silicates.The most common class of minerals? The Silicates. Diagnostic physical properties allow identification.Diagnostic physical properties allow identification. Gems are unusually rare and beautiful minerals. Gems are unusually rare and beautiful minerals.


Mineral NamesMineral Names Mineral names have a variety of origins.Mineral names have a variety of origins.

Words from other languages:Words from other languages:German—oGerman—orthoclase rthoclase (splits at right angles).(splits at right angles).Latin—Latin—albite albite (white).(white).

Properties:Properties:Color—Color—olivineolivine is olive green. is olive green.

Places:Places:Skutterudite—Skutterudite—Skutterud, Norway. Skutterud, Norway. Illite—Illite—First found in Illinois.First found in Illinois.

Composition:Composition:Chromite—Chromite—chromium bearing.chromium bearing.Borax—Borax—contains boron.contains boron.

People:People:Jimthompsonite—Jimthompsonite—after Harvard geologist James Thompson.after Harvard geologist James Thompson.


MineralogyMineralogy Scientific study of minerals started in the 16th century.Scientific study of minerals started in the 16th century.

1556—Georgius Agricola, a German physician1556—Georgius Agricola, a German physicianPublished Published De Re Metallica De Re Metallica ((On the Nature of MetalsOn the Nature of Metals))..Provided basic descriptions of minerals.Provided basic descriptions of minerals.

1669—Nicholas Steno, a Danish physician1669—Nicholas Steno, a Danish physicianDiscovered geometric properties.Discovered geometric properties. Initiated systematic description.Initiated systematic description.


MineralogyMineralogy Science has advanced the study of minerals.Science has advanced the study of minerals.

1828—minerals first studied under a microscope.1828—minerals first studied under a microscope. 1912—Max van Laue proposed X-ray study of minerals.1912—Max van Laue proposed X-ray study of minerals. 1915—William Henry and William Lawrence Bragg.1915—William Henry and William Lawrence Bragg.

The father and son team won the Nobel Prize.The father and son team won the Nobel Prize.Revealed the structure of minerals using X-rays.Revealed the structure of minerals using X-rays.X-ray diffraction (XRD) is still used to decipher minerals.X-ray diffraction (XRD) is still used to decipher minerals.

X-ray peaks plotted by a 1960s strip chart recorder.X-ray peaks plotted by a 1960s strip chart recorder.


MineralogyMineralogy Minerals are now studied using high-tech instruments.Minerals are now studied using high-tech instruments.

Probe the atomic structure of minerals.Probe the atomic structure of minerals.X-ray diffractometers—the same principle as in 1915.X-ray diffractometers—the same principle as in 1915.Electron microscopes and microprobes.Electron microscopes and microprobes.Mass spectrometers.Mass spectrometers.

Fig. A.8


Why Study Minerals?Why Study Minerals? Minerals are the building blocks of the planet.Minerals are the building blocks of the planet.

Minerals make up all of the rocks and sediments on Earth.Minerals make up all of the rocks and sediments on Earth. Understanding Earth requires understanding minerals.Understanding Earth requires understanding minerals.

Minerals are important to humans.Minerals are important to humans. Industrial minerals—Industrial minerals—raw materials for manufacturing.raw materials for manufacturing. Ore minerals—Ore minerals—sources of valuable metals.sources of valuable metals. Gem minerals—Gem minerals—attract human passions. attract human passions.

Another View


What Is a Mineral?What Is a Mineral? The geologic definition of a mineral is specialized:The geologic definition of a mineral is specialized:

Naturally occurring.Naturally occurring. Solid.Solid. Formed geologically.Formed geologically. Crystalline structure. Crystalline structure. Definite chemical Definite chemical

composition. composition. Mostly inorganic.Mostly inorganic.


What Is a Mineral?What Is a Mineral? They are naturally occurring.They are naturally occurring.

A true mineral is created by natural processes.A true mineral is created by natural processes. Humans can recreate natural processes to make minerals.Humans can recreate natural processes to make minerals.

These are called synthetic minerals.These are called synthetic minerals.


What Is a Mineral?What Is a Mineral? They are solid.They are solid.

A state of matter that can maintain its shape indefinitely.A state of matter that can maintain its shape indefinitely. Minerals are solids, not liquids or gases.Minerals are solids, not liquids or gases.


What Is a Mineral?What Is a Mineral? They are formed by geologic processes.They are formed by geologic processes.

Freezing from a melt.Freezing from a melt. Precipitation from a dissolved state in water.Precipitation from a dissolved state in water. Chemical reactions at high pressures and temperatures.Chemical reactions at high pressures and temperatures.

Subtle distinction: living organisms Subtle distinction: living organisms cancan create minerals. create minerals. Called Called biogenic mineralsbiogenic minerals to emphasize this special origin. to emphasize this special origin.

Vertebrate bones (apatite).Vertebrate bones (apatite).Oyster, mussel, andOyster, mussel, and

clam shells (aragonite).clam shells (aragonite).Other skeletal types.Other skeletal types.


They have a crystalline structure.They have a crystalline structure. Atoms in a mineral are arranged in a specific order.Atoms in a mineral are arranged in a specific order. This atomic pattern is called a crystal lattice.This atomic pattern is called a crystal lattice.

A solid with disordered atoms is called a glass.A solid with disordered atoms is called a glass. Lacking crystalline structure, glasses are not minerals.Lacking crystalline structure, glasses are not minerals.

What Is a Crystal?What Is a Crystal?

Fig. 5.4b


What Is a Mineral?What Is a Mineral? They have a definite chemical compositionThey have a definite chemical composition

Minerals can be defined by a chemical formula.Minerals can be defined by a chemical formula.Simple Simple

Ice—HIce—H22OO

Calcite—CaCOCalcite—CaCO33

Quartz—SiOQuartz—SiO22

ComplexComplex Biotite—K(Mg,Fe)Biotite—K(Mg,Fe)33(AlSi(AlSi33OO1010)(OH))(OH)22

Hornblende—CaHornblende—Ca22(Fe(Fe2+2+,Mg)(Al,Fe,Mg)(Al,Fe3+3+)(Si)(Si77Al)OAl)O2222(OH,F)(OH,F)22


What Is a Mineral?What Is a Mineral? They are mostly inorganicThey are mostly inorganic

Organic compoundsOrganic compoundsContain carbon–hydrogen bonds.Contain carbon–hydrogen bonds.Other elements may be present.Other elements may be present.

OxygenOxygen NitrogenNitrogen SulfurSulfur

Common products of living organisms.Common products of living organisms. Most minerals are NOT organic.Most minerals are NOT organic.


What Is a Crystal?What Is a Crystal? A single, continuous piece of crystalline solid. A single, continuous piece of crystalline solid. Typically bounded by flat surfaces (crystal faces).Typically bounded by flat surfaces (crystal faces). Crystal faces grow naturally as the mineral forms. Crystal faces grow naturally as the mineral forms. Crystals are sometimes prized mineral specimens.Crystals are sometimes prized mineral specimens.


What Is a Crystal?What Is a Crystal? Constancy of interfacial angles.Constancy of interfacial angles.

The same mineral has the same crystal faces.The same mineral has the same crystal faces. Adjacent faces occur at the same angle to one another. Adjacent faces occur at the same angle to one another.

Faces and angles reflect crystalline structure. Faces and angles reflect crystalline structure.

Fig. 5.5a


What Is a Crystal?What Is a Crystal? Crystals come in a variety of shapes. Crystals come in a variety of shapes. Many descriptive terms describe crystal shape. Many descriptive terms describe crystal shape.

Fig. 5.5b


What Is a Crystal?What Is a Crystal? People consider crystals to be special.People consider crystals to be special.

Regular geometric form.Regular geometric form. Crystals interact with light to create attractive beauty. Crystals interact with light to create attractive beauty.

Some think crystals possess magical powers. Some think crystals possess magical powers. Science reveals crystals do not affect health or mood. Science reveals crystals do not affect health or mood.


What Is inside a Crystal?What Is inside a Crystal? Ordered atoms like tiny balls packed tightly together.Ordered atoms like tiny balls packed tightly together. Held in place by chemical bonds. Held in place by chemical bonds. The way atoms are packed defines the crystal structure.The way atoms are packed defines the crystal structure. Physical properties (hardness, shape) depend upon:Physical properties (hardness, shape) depend upon:

Identity of atoms.Identity of atoms. Arrangement of atoms. Arrangement of atoms. Nature of atomic bonds. Nature of atomic bonds.

Sodium (Na+) and Chloride (Cl-) ions are bonded in a cubic lattice by ionic bonds to form the mineral Halite (NaCl), known as salt.Sodium (Na+) and Chloride (Cl-) ions are bonded in a cubic lattice by ionic bonds to form the mineral Halite (NaCl), known as salt. Fig. 5.6a,b


The type of atomic bonding governs mineral properties.The type of atomic bonding governs mineral properties. Stronger bonds = harder, higher melting points.Stronger bonds = harder, higher melting points. Weaker bonds = softer, lower melting points.Weaker bonds = softer, lower melting points.

Bonds may vary by direction in a mineral.Bonds may vary by direction in a mineral. Faster growth where bonds form more easily. Faster growth where bonds form more easily. The direction of weaker bonds controls breakage.The direction of weaker bonds controls breakage.

What Is inside a Crystal?What Is inside a Crystal?


What Is inside a Crystal?What Is inside a Crystal? The nature of atomic bonds controls characteristics.The nature of atomic bonds controls characteristics. 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.

Polymorph—same composition; different structure.Polymorph—same composition; different structure.

GraphiteGraphiteDiamondDiamond

Fig. 5.6c,d


Atomic PackingAtomic Packing Ionic radius (size) and ionic charge control packing. Ionic radius (size) and ionic charge control packing.

Ion—atom charged due to gain or loss of an electron.Ion—atom charged due to gain or loss of an electron. Cation—positive ion due to loss of electron(s).Cation—positive ion due to loss of electron(s). Anion—negative ion due to gain of electron(s).Anion—negative ion due to gain of electron(s).

Ionic size depends on # of electrons: anions are bigger.Ionic size depends on # of electrons: anions are bigger.

Fig. 5.7a


Atomic PackingAtomic Packing Ions pack together in different ways, depending on size.Ions pack together in different ways, depending on size.

Large central cation—larger number of anions.Large central cation—larger number of anions. Small central cation—smaller number of anions.Small central cation—smaller number of anions.

Packing configurations define a geometric shape.Packing configurations define a geometric shape.

CubicCubic OctahedralOctahedral TetrahedralTetrahedral

Fig. 5.7b


What Is inside a Crystal?What Is inside a Crystal? Ordered atoms in crystals form spectacular patterns. Ordered atoms in crystals form spectacular patterns. Atomic patterns repeat regularly in three dimensions. Atomic patterns repeat regularly in three dimensions. This 3-D internal pattern controls crystal shape.This 3-D internal pattern controls crystal shape.

Fig. 5.8


What Is inside a Crystal?What Is inside a Crystal? Ordered atomic patterns in minerals display symmetry.Ordered atomic patterns in minerals display symmetry.

Mirror image(s).Mirror image(s). Rotation about an axis (or axes).Rotation about an axis (or axes).

Symmetry characteristics are diagnostic.Symmetry characteristics are diagnostic.

Fig. 5.7c


How Do We “See” inside Crystals?How Do We “See” inside Crystals? X-ray diffraction (XRD) probes crystal lattices.X-ray diffraction (XRD) probes crystal lattices. Unique lattice spacing is used to ID minerals. Unique lattice spacing is used to ID minerals.

Box 5.2


How Do We “See” inside Crystals?How Do We “See” inside Crystals? Modern instruments allow us to “see” the atomic pattern.Modern instruments allow us to “see” the atomic pattern. Transmission electron microscope (TEM)Transmission electron microscope (TEM)

Shoots a beam of electrons at a crystal.Shoots a beam of electrons at a crystal. Electrons pass through spaces reaching a detector.Electrons pass through spaces reaching a detector. Electrons that interact with atoms don’t reach the detector.Electrons that interact with atoms don’t reach the detector. Dark and light pattern images the atomic crystal lattice.Dark and light pattern images the atomic crystal lattice.


New crystals can form in five ways. New crystals can form in five ways. Solidification from a melt.Solidification from a melt.

Crystals grow when the melt cools.Crystals grow when the melt cools.Atoms can’t remain unattached.Atoms can’t remain unattached.

Mineral FormationMineral Formation


New crystals can form in five ways. New crystals can form in five ways. Precipitation from a solution.Precipitation from a solution.

Seeds form when a solution becomes saturated.Seeds form when a solution becomes saturated.



New crystals can form in five ways.New crystals can form in five ways. Solid-state diffusion.Solid-state diffusion.



New crystals can form in five ways.New crystals can form in five ways. Biomineralization.Biomineralization.



New crystals can form in five ways.New crystals can form in five ways. Precipitating directly from a gas.Precipitating directly from a gas.



Mineral FormationMineral Formation A tiny early crystal acts as a seed for further growth.A tiny early crystal acts as a seed for further growth. Atoms migrate to the seed and attach to the outer face. Atoms migrate to the seed and attach to the outer face. Growth moves faces outward from the center.Growth moves faces outward from the center. Unique shape reflects the crystal’s internal atomic order.Unique shape reflects the crystal’s internal atomic order.

Time

Fig. 5.10a


Outward crystal growth fills available space.Outward crystal growth fills available space. Resulting crystal shape governed by surroundings.Resulting crystal shape 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.


Fig. 5.10b


Mineral FormationMineral Formation Mineral growth is often restricted by lack of space.Mineral growth is often restricted by lack of space.

Anhedral—grown in tight space, no crystal faces. Anhedral—grown in tight space, no crystal faces. Euhedral—grown in an open cavity, good crystal faces.Euhedral—grown in an open cavity, good crystal faces.

Anhedral crystals are much more prevalent. Anhedral crystals are much more prevalent. Euhedral crystals grow into the open space in a geode.Euhedral crystals grow into the open space in a geode.

Amethyst GeodeAmethyst Geode

Fig. 5.10d


Mineral DestructionMineral Destruction Minerals can be destroyed by:Minerals can be destroyed by:

Melting—heat breaks the bonds holding atoms together.Melting—heat breaks the bonds holding atoms together. Dissolving—solvents (mostly water) break atomic bonds.Dissolving—solvents (mostly water) break atomic bonds. Chemical reaction—reactive materials break bonds.Chemical reaction—reactive materials break bonds.

Chapter 9 Opener


Mineral IdentificationMineral Identification Mineral identification is a skill.Mineral identification is a skill.

Requires learning diagnostic properties.Requires learning diagnostic properties.Some properties are easily seen.Some properties are easily seen.

ColorColor Crystal shapeCrystal shape

Some properties require handling or testing.Some properties require handling or testing. HardnessHardness Specific gravitySpecific gravity


Physical PropertiesPhysical Properties Common PropertiesCommon Properties

ColorColor StreakStreak LusterLuster HardnessHardness Specific gravitySpecific gravity Crystal habitCrystal habit Fracture or cleavageFracture or cleavage


ColorColor The part of visible light that is not absorbed by a mineral.The part of visible light that is not absorbed by a mineral. Diagnostic for some minerals.Diagnostic for some minerals.

Olivine is olive green.Olivine is olive green. Some minerals exhibit a broad color range.Some minerals 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.

Fig. 5.11a


StreakStreak Color of a powder produced by crushing a mineral.Color of a powder produced by crushing a mineral. Obtained by scraping a mineral on unglazed porcelain.Obtained by scraping a mineral on unglazed porcelain.

Streak color is less variable than crystal color.Streak color is less variable than crystal color.

Fig. 5.11b


LusterLuster 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.

SilkySilkyVitreous (glassy)Vitreous (glassy)SatinySatinyResinousResinousPearlyPearlyEarthy (dull)Earthy (dull)Adamantine (brilliant)Adamantine (brilliant)

Satin spar Gypsum – Satiny lusterSatin spar Gypsum – Satiny luster

Quartz – Vitreous lusterQuartz – Vitreous luster


HardnessHardness Scratching resistance of a mineral.Scratching resistance of a mineral. Derives from the strength of atomic bonds. Derives from the strength of atomic bonds. Hardness compared to the Mohs scale for hardness.Hardness compared to the Mohs scale for hardness.

1.1. Talc, graphiteTalc, graphite

2.2. GypsumGypsum

3.3. CalciteCalcite

4.4. FluoriteFluorite

5.5. ApatiteApatite

6.6. Orthoclase Orthoclase

7.7. QuartzQuartz

8.8. TopazTopaz

9.9. CorundumCorundum

10.10. DiamondDiamond

Glass - Steel 5.5

Fingernail 2.5

Copper Penny 3.5

Steel File 6.5

Table 5.1


Specific GravitySpecific Gravity Represents the density of a mineral.Represents the density of a mineral. Mineral weight over the weight of an equal water volume.Mineral weight over the weight of an equal water volume. Specific gravity is “heft”—how heavy it feels.Specific gravity is “heft”—how heavy it feels.

Galena—heavy (SG 7.60).Galena—heavy (SG 7.60). Quartz—light (SG 2.65).Quartz—light (SG 2.65).

Galena “feels” heavier than quartz.Galena “feels” heavier than quartz.


Crystal HabitCrystal Habit A single crystal with well-formed faces, orA single crystal with well-formed faces, or An aggregate of many well-formed crystals.An aggregate of many well-formed crystals. Arrangement of faces reflects internal atomic structure.Arrangement of faces reflects internal atomic structure. Records variation in directional growth rates.Records variation in directional growth rates.

Blocky or equant—equal growth rate in three dimensions.Blocky or equant—equal growth rate in three dimensions. Bladed—shaped like a knife blade.Bladed—shaped like a knife blade. Needle-like—rapid growth in one dimension, slow in others.Needle-like—rapid growth in one dimension, slow in others.


Special Physical PropertiesSpecial Physical Properties Special physical properties.Special physical properties.

Effervescence—reactivity with acid.Effervescence—reactivity with acid. Magnetism—magnetic attraction.Magnetism—magnetic attraction. Taste—self-explanatory.Taste—self-explanatory. Smell—self-explanatory.Smell—self-explanatory. Feel—tactile response.Feel—tactile response. Elasticity—response to bending.Elasticity—response to bending. Diaphaneity—relative transparency.Diaphaneity—relative transparency. Piezoelectricity—electric charge when squeezed.Piezoelectricity—electric charge when squeezed. Pyroelectricity—electric charge when heated.Pyroelectricity—electric charge when heated. Refractive index—degree of bending light.Refractive index—degree of bending light. Malleability—ability to be pounded into thin sheets.Malleability—ability to be pounded into thin sheets. Ductility—ability to be drawn into thin wires.Ductility—ability to be drawn into thin wires. Sectility—ability to be shaved with a knife.Sectility—ability to be shaved with a knife.

Magnetite crystals on a large magnet.Magnetite crystals on a large magnet.


FractureFracture Minerals break in ways that reflect atomic bonding. Minerals break in ways that reflect atomic bonding. Fracturing implies equal bond strength in all directions.Fracturing implies equal bond strength in all directions.

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.Volcanic glass was used by native cultures to make tools.Volcanic glass was used by native cultures to make tools.


CleavageCleavage Tendency to break along planes of weaker atomic bonds. Tendency to break along planes of weaker atomic bonds. 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 throughgoing; it often forms parallel steps.Cleavage is throughgoing; it often forms parallel steps. Crystal faces only occur on external surfaces. Crystal faces only occur on external surfaces.

1, 2, 3, 4, and 6 are cleavages possible. 1, 2, 3, 4, and 6 are cleavages possible.

Fig. 5.12g


Cleavage Cleavage Examples of cleavageExamples of cleavage

One directionOne direction

Two directions at 90ºTwo directions at 90º

Two directions NOT at 90ºTwo directions NOT at 90º

Potassium FeldsparPotassium Feldspar

Muscovite micaMuscovite mica

AmphiboleAmphiboleFig. 5.12a,b,c


Cleavage Cleavage Examples of cleavageExamples of cleavage

Three directions at 90ºThree directions at 90º

Three directions NOT at 90ºThree directions NOT at 90º

CalciteCalcite

HaliteHalite

Fig. 5.12d,e


Mineral ClassificationMineral Classification Minerals can be separated into a few groups.Minerals can be separated into a few groups. J. J. Berzelius, a Swedish chemist, noted similarities.J. J. Berzelius, a Swedish chemist, noted similarities.

Minerals can be separated by:Minerals can be separated by:The principal anion (negative ion), orThe principal anion (negative ion), orAnionic group (negative molecule).Anionic group (negative molecule).

Example: sulfides (SExample: sulfides (S--) or carbonates (CO) or carbonates (CO332-2-))

The most important mineral class is the silicates (SiOThe most important mineral class is the silicates (SiO444-4-).).


The Mineral ClassesThe Mineral Classes Minerals are classified by their dominant anion.Minerals are classified by their dominant anion.

Silicates (SiOSilicates (SiO224-4-) are called the rock forming minerals.) are called the rock forming minerals.

Constitute almost the entire crust and mantle of Earth.Constitute almost the entire crust and mantle of Earth. They are the most common minerals.They are the most common minerals. Example: quartz (SiOExample: quartz (SiO22))


Mineral ClassesMineral Classes Oxides (OOxides (O2-2-)) Metal cations (FeMetal cations (Fe2+2+, Fe, Fe3+3+, Ti, Ti2+2+) bonded to oxygen.) bonded to oxygen. Examples:Examples:

Magnetite (FeMagnetite (Fe33OO44))

Hematite (FeHematite (Fe22OO33))

Rutile (TiORutile (TiO22))


Mineral ClassesMineral Classes Sulfides (SSulfides (S--)) Metal cations bonded to a sulfide anion.Metal cations bonded to a sulfide anion. Examples:Examples:

Pyrite (FeSPyrite (FeS22)) Galena (PbS)Galena (PbS) Sphalerite (ZnS)Sphalerite (ZnS)


Mineral ClassesMineral Classes Sulfates (SOSulfates (SO44

2-2-)) Metal cation bonded to a sulfate anionic group.Metal cation bonded to a sulfate anionic group. Many sulfates form by evaporation of seawater. Many sulfates form by evaporation of seawater. Examples:Examples:

Gypsum (CaSOGypsum (CaSO442H2H22O)O)

Anhydrite (CaSOAnhydrite (CaSO44))


Mineral ClassesMineral Classes Minerals are classified by their dominant anion.Minerals are classified by their dominant anion.

Halides (ClHalides (Cl-- or F or F--)) Examples:Examples:

Fluorite (CaFFluorite (CaF22))

Halite (NaCl)Halite (NaCl)



Carbonates (COCarbonates (CO332-2-))

Examples:Examples:Calcite (CaCO3)Calcite (CaCO3)Dolomite (Ca,Mg[CODolomite (Ca,Mg[CO33]]22))



Native elements (Cu, Au, Ag)Native elements (Cu, Au, Ag) Pure masses of a single metalPure masses of a single metal Examples:Examples:

Copper (Cu)Copper (Cu)Gold (Au)Gold (Au)


Mineral ClassificationMineral Classification 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.

Oxygen Oxygen OO 46.6%46.6% SiliconSilicon SiSi 27.7%27.7% Aluminum Aluminum AlAl 8.1% 8.1% IronIron FeFe 5.0% 5.0% Calcium Calcium CaCa 3.6% 3.6% Sodium Sodium NaNa 2.8% 2.8% Potassium Potassium KK 2.6% 2.6% Magnesium Magnesium MgMg 2.1% 2.1% All others All others 1.5% 1.5%

74.3% of crustal minerals! 74.3% of crustal minerals!


Silicates are know as “the rock-forming minerals.” Silicates are know as “the rock-forming minerals.” They dominate Earth’s crust and mantle. They dominate Earth’s crust and mantle.

Made of oxygen and silicon with other atoms.Made of oxygen and silicon with other atoms.

Silicate MineralsSilicate Minerals


The SiOThe SiO444- 4- anionic unit: the silicon-oxygen tetrahedron.anionic unit: the silicon-oxygen tetrahedron.

Four O atoms are bonded to a central Si atom.Four O atoms are bonded to a central Si atom. Define the corners of a four-sided geometric figure. Define the corners of a four-sided geometric figure. The “silica tetrahedron” is the building block of silicates.The “silica tetrahedron” is the building block of silicates. The silica tetrahedron can be portrayed in different ways:The silica tetrahedron can be portrayed in different ways:

Spheres.Spheres.A ball and stick model.A ball and stick model.Polyhedra. Polyhedra.

Silicate MineralsSilicate Minerals

Fig. 5.13a


Silicate MineralsSilicate Minerals Silicates are divided into several groups.Silicates are divided into several groups.

Based on how silica tetrahedra are arranged.Based on how silica tetrahedra are arranged. The groups vary by how silica tetrahedra share oxygen.The groups vary by how silica tetrahedra share oxygen. The amount of shared oxygen determines the Si:O ratio.The amount of shared oxygen determines the Si:O ratio.

Si:O ratio is an important control on:Si:O ratio is an important control on: Melting temperature.Melting temperature. Mineral structure and cations present. Mineral structure and cations present. Susceptibility to chemical weathering. Susceptibility to chemical weathering.


Silicate MineralsSilicate Minerals Independent Tetrahedra—Si:O 1:4Independent Tetrahedra—Si:O 1:4

Silica tetrahedra share no oxygens.Silica tetrahedra share no oxygens. They are linked by cations.They are linked by cations. Examples: Examples:

Olivine—a glassy green mineralOlivine—a glassy green mineralGarnet—forms equant, 12-sided crystalsGarnet—forms equant, 12-sided crystals

Fig. 5.13b


Silicate MineralsSilicate Minerals Single Chains—Si:O 1:3Single Chains—Si:O 1:3

Silica tetrahedra link to share two oxygens.Silica tetrahedra link to share two oxygens. Example: Example:

Pyroxenes Pyroxenes Dark, long crystals Dark, long crystals Two cleavages near 90°Two cleavages near 90°

Fig. 5.13b


Silicate MineralsSilicate Minerals Double chains—Si:O 2:7Double chains—Si:O 2:7

Silica tetrahedra alternate sharing two and three oxygens. Silica tetrahedra alternate sharing two and three oxygens. Example:Example:

AmphibolesAmphiboles Dark, long crystalsDark, long crystals Two cleavages at 60° and 120°Two cleavages at 60° and 120°

Fig. 5.13b


Silicate MineralsSilicate Minerals Sheet silicates—Si:O 2:5Sheet silicates—Si:O 2:5

Silica tetrahedra share three oxygens.Silica tetrahedra share three oxygens. Create two-dimensional flat sheets of linked tetrahedra.Create two-dimensional flat sheets of linked tetrahedra. Characterized by one direction of perfect cleavage.Characterized by one direction of perfect cleavage. Examples: MicasExamples: Micas

Biotite (dark)Biotite (dark)Muscovite (light)Muscovite (light)

Fig. 5.12a, 5.13b


Silicate MineralsSilicate Minerals Framework silicates—Si:O 1:2Framework silicates—Si:O 1:2

All four oxygens in each silica tetrahedra are shared.All four oxygens in each silica tetrahedra are shared. Examples:Examples:

Feldspars—plagioclase and potassium feldsparFeldspars—plagioclase and potassium feldsparSilica (quartz) group—contains only Si and OSilica (quartz) group—contains only Si and O

Fig. 5.13b


GemsGems Gemstones—a mineral with special value. Gemstones—a mineral with special value.

Rare—formed by unusual geological processes.Rare—formed by unusual geological processes. Beautiful—strikingly unique color, clarity, and luster.Beautiful—strikingly unique color, clarity, and luster.

Gem—a cut and polished stone created for jewelry.Gem—a cut and polished stone created for jewelry. Precious—stones that are particularly rare and expensive.Precious—stones that are particularly rare and expensive.

DiamondDiamondRubyRubySapphireSapphire

Semiprecious—less rare.Semiprecious—less rare.TourmalineTourmalineTopazTopazAquamarineAquamarineGarnetGarnet

Fig. 5.14


GemsGems Gems are cut and polished stones used in jewelry.Gems are cut and polished stones used in jewelry.

Facets are ground onto a gem by a lapidary machine.Facets are ground onto a gem by a lapidary machine. Faceting a gemstone takes a lot of time and effort. Faceting a gemstone takes a lot of time and effort. Facets are not natural crystal faces.Facets are not natural crystal faces.

Fig. 5.15b,c


Whence Diamonds?Whence Diamonds? Diamonds originate under extremely high pressure.Diamonds originate under extremely high pressure.

~150 km deep—in the upper mantle.~150 km deep—in the 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.

Box 5.3


The Mineralogical Society of AmericaThe Mineralogical Society of America http://www.minsocam.org/

USGS Mineral Resources ProgramUSGS Mineral Resources Program http://minerals.usgs.gov/

USGS Mineral Resources On-Line Spatial DataUSGS Mineral Resources On-Line Spatial Data http://tin.er.usgs.gov/

David Barthelmy’s Mineralogy DatabaseDavid Barthelmy’s Mineralogy Database http://webmineral.com/

The Mineralogical RecordThe Mineralogical Record http://www.mineralogicalrecord.com/contents.asp

Mindat.org—the Largest Mineral Database on the InternetMindat.org—the Largest Mineral Database on the Internet http://www.mindat.org/

Useful Web ResourcesUseful Web Resources


Photo CreditsPhoto Credits Ronald L. Parker, slides 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, Ronald L. Parker, slides 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,

15, 16, 17, 20, 22, 28, 30, 31, 32, 33, 34, 39, 40, 41, 43, 45, 15, 16, 17, 20, 22, 28, 30, 31, 32, 33, 34, 39, 40, 41, 43, 45, 46, 47, 48, 50, 52, 54, 55, 56, 57, 58, 59, 60, 61, 63, 64, 66, 46, 47, 48, 50, 52, 54, 55, 56, 57, 58, 59, 60, 61, 63, 64, 66, 68. 68.


W. W. Norton & CompanyW. W. Norton & CompanyIndependent and Employee-OwnedIndependent and Employee-Owned

This concludes the Norton Media LibraryThis concludes the Norton Media LibraryPowerPoint Slide Set for PowerPoint Slide Set for Chapter 5

Earth: Portrait of a PlanetEarth: Portrait of a Planet

4th Edition (2011)4th Edition (2011)

by Stephen Marshakby Stephen Marshak

PowerPoint slides prepared by PowerPoint slides prepared by

Ronald L. ParkerRonald L. ParkerSenior Geologist, Senior Geologist,

Fronterra Geosciences, Fronterra Geosciences,

Denver, ColoradoDenver, Colorado

earth lecture slide chapter five

Education

minerals minerals

study minerals

mineralogy minerals

understanding minerals

beautiful minerals

biogenic minerals

synthetic minerals

new minerals