understanding earth sixth edition chapter 3: earth materials minerals and rocks © 2011 by w. h....

Understanding EarthSixth Edition

Chapter 3:EARTH MATERIALSMinerals and Rocks

Grotzinger • Jordan

Chapter 3:Chapter 3: Earth Earth

Materials:Materials:Minerals and Minerals and

RocksRocks

About Earth MaterialsAbout Earth Materials

• All Earth materials are composed of All Earth materials are composed of atoms bound together.atoms bound together.

• Minerals are composed of atoms bonded Minerals are composed of atoms bonded together and are the building blocks of together and are the building blocks of rocks. rocks.

• Rocks are composed of minerals and Rocks are composed of minerals and they record various geologic processes.they record various geologic processes.

Lecture OutlineLecture Outline

1.1. What are minerals?What are minerals?

2. The structure of matter2. The structure of matter

3. The formation of minerals3. The formation of minerals

4. Classes of rock-forming minerals4. Classes of rock-forming minerals

5. Physical properties of minerals5. Physical properties of minerals

6. What are rocks?6. What are rocks?

Lecture OutlineLecture Outline

7. The rock cycle: interactions between 7. The rock cycle: interactions between the plate tectonic and climate systemsthe plate tectonic and climate systems

8. Concentrations of valuable mineral 8. Concentrations of valuable mineral resourcesresources

1. What Are Minerals?1. What Are Minerals?

Minerals are the building Minerals are the building blocks of rocks. blocks of rocks.

1. What Are Minerals?What Are Minerals?

Geologists define mineral as a Geologists define mineral as a naturally occurring, solid, naturally occurring, solid, crystalline substance, usually crystalline substance, usually inorganic, with a specific inorganic, with a specific chemical composition. chemical composition.

1. What Are Minerals?What Are Minerals?

Naturally occurringNaturally occurring = found in nature = found in nature

Solid, crystalline substanceSolid, crystalline substance = atoms are = atoms are arranged in orderly patternsarranged in orderly patterns

Usually inorganicUsually inorganic = not a product of living = not a product of living tissuetissue

With a specific chemical formulaWith a specific chemical formula = unique = unique chemical compositionchemical composition

Thought questions for this chapterThought questions for this chapter

Coal, a natural organic substance that forms from Coal, a natural organic substance that forms from decaying vegetation, is not considered to be a mineral. decaying vegetation, is not considered to be a mineral. However, when coal is heated to high temperatures and However, when coal is heated to high temperatures and buried under high pressures, it is transformed into the buried under high pressures, it is transformed into the mineral graphite. Why is it, then, that coal is not mineral graphite. Why is it, then, that coal is not considered a mineral, but graphite is? Explain your considered a mineral, but graphite is? Explain your reasoning.reasoning.

2. The Structure of Matter2. The Structure of Matter

The atom is the smallest unit The atom is the smallest unit of an element that retains the of an element that retains the physical and chemical physical and chemical properties of that element. properties of that element.

Atomic nucleusAtomic nucleus: protons and : protons and neutrons. neutrons.

ElectronsElectrons: cloud of moving particles : cloud of moving particles surrounding the nucleus.surrounding the nucleus.

Example: the carbon atom (C)Example: the carbon atom (C)

The Carbon Atom

electron cloud

atomic nucleus

The Carbon Atom

electron cloud

atomic nucleus

carbon has 6electrons…

The Carbon Atom

electron cloud

atomic nucleus

electron (–)

proton (+)

neutron

The Carbon Atom

electron cloud

atomic nucleus

…and a nucleusof 6 protons …

electron (–)

proton (+)

neutron

The Carbon Atom

electron cloud

atomic nucleus

Carbon has 6electrons…

…and a nucleusof 6 protons …

…and 6 neutrons having no charge.

electron (–)

proton (+)

neutron

IsotopesIsotopes – atoms of the same element – atoms of the same element with different numbers of protons. with different numbers of protons.

Example: the carbon atom (C) typically Example: the carbon atom (C) typically has 6 neutrons and 6 protons (called has 6 neutrons and 6 protons (called CC1212), but there are also small amounts ), but there are also small amounts of Cof C1313 and C and C1414..

Chemical reactions – interactions Chemical reactions – interactions of the atoms of two or more of the atoms of two or more elements in certain fixed elements in certain fixed proportions. proportions.

Example: H + H + O = HExample: H + H + O = H22OO

Example: Na + Cl = NaClExample: Na + Cl = NaCl

Chemical compounds that are Chemical compounds that are minerals form by: minerals form by:

electron sharingelectron sharingoror

electron transferelectron transfer

Electron Sharing:Electron Sharing:

Carbon atoms in a diamondCarbon atoms in a diamond

Electron Transfer:Electron Transfer:

Sodium (Na) + chlorine (Cl) = Sodium (Na) + chlorine (Cl) = NaCl (halite)NaCl (halite)

Electron Transfer:Electron Transfer:

Sodium (Na) + chlorine (Cl) = Sodium (Na) + chlorine (Cl) = NaCl (halite)NaCl (halite)

Each sodium ion (circled in red) Each sodium ion (circled in red) is surrounded by 6 chloride ions is surrounded by 6 chloride ions (circled in yellow), and vice versa.(circled in yellow), and vice versa.

3. The Structure of Minerals3. The Structure of Minerals

How do minerals form?How do minerals form?

Crystallization –Crystallization –

atoms come togetheratoms come togetherin the proper proportionin the proper proportionand proper arrangementand proper arrangement

Electrical charges of atomic ionsElectrical charges of atomic ions

Cation – positively chargedCation – positively charged

Anion – negatively chargedAnion – negatively charged

Atomic ions arrange themselves Atomic ions arrange themselves according to charge and size.according to charge and size.

The forces of electrical attraction between The forces of electrical attraction between protons (+) and electrons (-) that hold protons (+) and electrons (-) that hold minerals and other chemical compounds minerals and other chemical compounds together together

covalent bondscovalent bondsionic bondsionic bondsmetallic bondsmetallic bonds

When do minerals form?When do minerals form?

• During cooling of molten rockDuring cooling of molten rock

• During evaporation of waterDuring evaporation of water

• Upon changes in temperature Upon changes in temperature and pressure on existing and pressure on existing mineralsminerals

Chemical classes of minerals:Chemical classes of minerals:

• Silicates – contain O and SiSilicates – contain O and Si• Carbonates – contain C and OCarbonates – contain C and O• Oxides – contain O and Oxides – contain O and

metallic cationsmetallic cations• Sulfides – contain S and metallic Sulfides – contain S and metallic

cationscations• Sulfates – contain SOSulfates – contain SO44 and metallic and metallic

cationscations

4. Classes of Rock-forming Minerals4. Classes of Rock-forming Minerals

Chemical classes (Chemical classes (cont.)cont.)::

• Halides – contain Cl, F, I, or BrHalides – contain Cl, F, I, or Br• Hydroxides – contain OHHydroxides – contain OH• Native elements – masses of all Native elements – masses of all

the same element metallically the same element metallically bondedbonded

Silicate ion (SiO44–)

Oxygen ions(O2–) Silicon ion

(Si4+)

Formation of silicate mineralsFormation of silicate minerals

Oxygen ions(O2–)

The silicate ion forms tetrahedra.

Silicon ion(Si4+)

(Si4+)

Quartzstructure

(Si4+)

Quartzstructure

Quartz is a silicate polymorph.

(Si4+)

Quartzstructure

Tetrahedra are the basic building blocks of all silicate minerals. About 95% of Earth’s minerals are silicates.

Draw a simple diagram to show how silicon and oxygen in Draw a simple diagram to show how silicon and oxygen in silicate minerals share electrons.silicate minerals share electrons.

Types of silicate minerals:Types of silicate minerals:

Isolated silica tetrahedraIsolated silica tetrahedra

Single-chain linkagesSingle-chain linkages

Double-chain linkagesDouble-chain linkages

Sheet linkagesSheet linkages

FrameworksFrameworks

Mineral Chemical formula

Cleavage planesand number of

cleavage directionsSilicate

structure Specimen

1 plane Isolatedtetrahedra

Olivine (Mg, Fe)2SiO4

structure Specimen

2 planes at 90°Single chains

Olivine

Pyroxene

(Mg, Fe)2SiO4

(Mg, Fe)SiO3

structure Specimen

2 planes at 60°and 120° Double chains

Olivine

Pyroxene

Amphibole

(Mg, Fe)2SiO4

(Mg, Fe)SiO3

Ca2(Mg, Fe)5Si8O22(OH)2

structure Specimen

1 plane Sheets

Olivine

Pyroxene

Amphibole

(Mg, Fe)2SiO4

(Mg, Fe)SiO3

Muscovite:KAl2(AlSi3O10)(OH)2

Biotite:K(Mg, Fe)3AlSi3O10(OH)2

structure Specimen

1 plane Sheets

Olivine

Pyroxene

Amphibole

Feldspars

2 planes at 90° Three-dimensionalframework

(Mg, Fe)2SiO4

(Mg, Fe)SiO3

Muscovite:KAl2(AlSi3O10)(OH)2

Biotite:K(Mg, Fe)3AlSi3O10(OH)2

Orthoclase feldspar:KAlSi3O8

Plagioclase feldspar: (Ca, Na) AlSi3O8

Diopside, a pyroxene, has the formula (Ca, Mg)Diopside, a pyroxene, has the formula (Ca, Mg)22SiSi22OO66. .

What does that tell you about its crystal structure and What does that tell you about its crystal structure and cation substitution?cation substitution?

What physical properties of sheet silicates are related toWhat physical properties of sheet silicates are related totheir crystal structure?their crystal structure?

5. Physical Properties of Minerals5. Physical Properties of Minerals

HardnessHardness

CleavageCleavage

Fracture Fracture

LusterLuster

ColorColor

StreakStreak

DensityDensity

Crystal habitCrystal habit

Uses of physical properties:Uses of physical properties:

Mineral identificationMineral identification

Industrial application of Industrial application of mineralsminerals

Mica and itsMica and itscleavagecleavage

5. Physical Properties of Minerals5. Physical Properties of MineralsPyrite andPyrite andits crystalits crystalhabithabit

5. Physical Properties of Minerals5. Physical Properties of MineralsCalcite and itsCalcite and itscleavagecleavage

Hematite and Hematite and its streakits streak

Aragonite, with a density of 2.9 g/cmAragonite, with a density of 2.9 g/cm33, has exactly the , has exactly the same chemical composition as calcite, which has a same chemical composition as calcite, which has a density of 2.7 g/cmdensity of 2.7 g/cm33. Other things being equal, which of . Other things being equal, which of these two minerals is more likely to have formed under these two minerals is more likely to have formed under high pressure?high pressure?

There are at least seven physical properties one can There are at least seven physical properties one can use to identify an unknown mineral. Which ones are most use to identify an unknown mineral. Which ones are most useful in discriminating between minerals that look useful in discriminating between minerals that look similar? Describe a strategy that would allow you to similar? Describe a strategy that would allow you to prove that an unknown clear calcite crystal is not the prove that an unknown clear calcite crystal is not the same mineral as a known clear crystal of quartz.same mineral as a known clear crystal of quartz.

Choose two minerals from Appendix 4 that you think Choose two minerals from Appendix 4 that you think might make good abrasive or grinding stones for might make good abrasive or grinding stones for sharpening steel, and describe the physical properties sharpening steel, and describe the physical properties that cause you to believe they would be suitable for thatthat cause you to believe they would be suitable for thatpurpose.purpose.

6. What Are Rocks?6. What Are Rocks?

Rocks are naturally occurring solid Rocks are naturally occurring solid aggregates of minerals, or in some aggregates of minerals, or in some cases, non-mineral solid matter.cases, non-mineral solid matter.

Identity is determined by:Identity is determined by:

texturetexturecompositioncomposition

Rocks are classified into three Rocks are classified into three groups:groups:

IgneousIgneous

SedimentarySedimentary

MetamorphicMetamorphic

Igneous RocksIgneous Rocks

Sedimentary RocksSedimentary Rocks

Metamorphic RocksMetamorphic Rocks

In some bodies of granite, we can find very large crystals, In some bodies of granite, we can find very large crystals, some as much as a meter across, yet these crystals tend some as much as a meter across, yet these crystals tend to have few crystal faces. What can you deduce about the to have few crystal faces. What can you deduce about the conditions under which these large crystals grew?conditions under which these large crystals grew?

Which igneous intrusion would you expect to have a wider Which igneous intrusion would you expect to have a wider contact metamorphic zone: one intruded by a very hot contact metamorphic zone: one intruded by a very hot magma or one intruded by a cooler magma?magma or one intruded by a cooler magma?

Where are igneous rocks most likely to be found? How Where are igneous rocks most likely to be found? How could you be certain that the rocks were igneous and not could you be certain that the rocks were igneous and not sedimentary or metamorphic?sedimentary or metamorphic?

7. The Rock Cycle7. The Rock Cycle

Interactions between the plate Interactions between the plate tectonic and climate systemstectonic and climate systems

7. The Rock Cycle7. The Rock Cycle

What geologic processes transform a sedimentary rock What geologic processes transform a sedimentary rock into an igneous rock?into an igneous rock?

Describe the geologic processes by which an igneous Describe the geologic processes by which an igneous rock is transformed into a metamorphic rock and then rock is transformed into a metamorphic rock and then exposed to erosion.exposed to erosion.

Using the rock cycle, trace the path from a magma to a Using the rock cycle, trace the path from a magma to a granitic intrusion to a metamorphic gneiss to a sandstone. granitic intrusion to a metamorphic gneiss to a sandstone. Be sure to include the roles of the plate tectonics climate Be sure to include the roles of the plate tectonics climate systems and the specific processes that create rocks.systems and the specific processes that create rocks.

8. Concentrations of Valuable 8. Concentrations of Valuable Mineral ResourcesMineral Resources

Types of ore minerals:Types of ore minerals:

Vein depositsVein deposits

Disseminated depositsDisseminated deposits

Igneous depositsIgneous deposits

Sedimentary depositsSedimentary deposits

Deformedcountry rock Geysers and

hot springs

Plutonicintrusion

MagmaMagma

GroundwaterGroundwater

Origin of vein Origin of vein depositsdeposits

hot springs

Plutonicintrusion

MagmaMagma

Groundwater dissolves metal oxidesand sulfides. Heated by the magma, it rises, precipitating metal ores in joints.

hot springs

Plutonicintrusion

MagmaMagma

Groundwater dissolves metal oxidesand sulfides. Heated by the magma, it rises, precipitating metal ores in joints.

Vein depositVein deposit

Typical sulfide minerals from vein depositsTypical sulfide minerals from vein deposits

Open-pit mine for disseminated Open-pit mine for disseminated deposits of copper-bearing minerals.deposits of copper-bearing minerals.

Igneous depositsIgneous deposits

Chromitelayers (dark)in layeredigneous rock

Sedimentary deposits:Sedimentary deposits:

Copper, iron, other metalsCopper, iron, other metals

Gold, diamonds, other Gold, diamonds, other heavy minerals (placers)heavy minerals (placers)

Back in the late 1800s, gold miners used to pan for gold Back in the late 1800s, gold miners used to pan for gold by placing sediment from rivers in a pan and filtering by placing sediment from rivers in a pan and filtering water through the pan while swirling the pan’s contents. water through the pan while swirling the pan’s contents. The miners wanted to be certain that they had found real The miners wanted to be certain that they had found real gold and not pyrite (“fool’s gold”). Why did this method gold and not pyrite (“fool’s gold”). Why did this method work? What mineral property does the process of work? What mineral property does the process of panning for gold use? What is another possible method panning for gold use? What is another possible method for distinguishing between gold and pyrite?for distinguishing between gold and pyrite?

AnionAnionAtomic massAtomic massAtomic numberAtomic numberBeddingBeddingBiological sedimentBiological sedimentCarbonateCarbonateCationCationChemical sedimentsChemical sedimentsCleavageCleavageColorColorContact metamorphismContact metamorphismCovalent bondCovalent bondCrystalCrystalCrystal habitCrystal habit

Key terms and conceptsKey terms and concepts

DensityDensityDisseminated depositDisseminated depositElectron sharingElectron sharingElectron transferElectron transferErosionErosionFractureFractureGrainGrainHardnessHardnessHydrothermal solutionHydrothermal solutionIgneous rockIgneous rockIonIonIonic bondIonic bondIsotopeIsotopeLithificationLithification

LusterLusterMagmaMagmaMetallic bondMetallic bondMetamorphic rockMetamorphic rockMineralMineralMineralogyMineralogyMohs scale of hardnessMohs scale of hardnessOreOreOxidesOxidesPolymorphPolymorphPrecipitatePrecipitateRegional metamorphismRegional metamorphismRockRockRock cycleRock cycle

SedimentSedimentSedimentary rockSedimentary rockSilicateSilicateSiliclastic sedimentsSiliclastic sedimentsSpecific gravitySpecific gravityStreakStreakSulfateSulfateSulfideSulfideTextureTextureTrace elementTrace elementVeinVeinWeatheringWeathering

understanding earth sixth edition chapter 3: earth materials minerals and rocks © 2011 by w. h....

carbon atoms

minerals form

carbon atom c2

crystallization atoms

structure of matterthe

structure of mineralshow

structure of matter3

mineral graphite

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