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Understanding EarthSixth Edition
Chapter 3:EARTH MATERIALSMinerals and Rocks
© 2011 by W. H. Freeman and Company
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)
2. The Structure of Matter2. The Structure of Matter
The Carbon Atom
electron cloud
atomic nucleus
The Carbon Atom
electron cloud
atomic nucleus
carbon has 6electrons…
The Carbon Atom
electron cloud
atomic nucleus
carbon has 6electrons…
electron (–)
proton (+)
neutron
The Carbon Atom
electron cloud
atomic nucleus
carbon has 6electrons…
…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..
2. The Structure of Matter2. The Structure of Matter
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
2. The Structure of Matter2. The Structure of Matter
Chemical compounds that are Chemical compounds that are minerals form by: minerals form by:
electron sharingelectron sharingoror
electron transferelectron transfer
2. The Structure of Matter2. The Structure of Matter
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.
3. The Structure of Minerals3. The Structure of Minerals
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
3. The Structure of Minerals3. The Structure of Minerals
3. The Structure of Minerals3. The Structure of Minerals
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
3. The Structure of Minerals3. The Structure of Minerals
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
4. Classes of Rock-forming Minerals4. Classes of Rock-forming Minerals
Silicate ion (SiO44–)
Oxygen ions(O2–) Silicon ion
(Si4+)
Formation of silicate mineralsFormation of silicate minerals
4. Classes of Rock-forming Minerals4. Classes of Rock-forming Minerals
Silicate ion (SiO44–)
Oxygen ions(O2–)
The silicate ion forms tetrahedra.
Silicon ion(Si4+)
Silicate ion (SiO44–)
Oxygen ions(O2–) Silicon ion
(Si4+)
The silicate ion forms tetrahedra.
Quartzstructure
Silicate ion (SiO44–)
Oxygen ions(O2–) Silicon ion
(Si4+)
The silicate ion forms tetrahedra.
Quartzstructure
Quartz is a silicate polymorph.
Silicate ion (SiO44–)
Oxygen ions(O2–) Silicon ion
(Si4+)
The silicate ion forms tetrahedra.
Quartzstructure
Tetrahedra are the basic building blocks of all silicate minerals. About 95% of Earth’s minerals are silicates.
Thought questions for this chapterThought questions for this chapter
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
4. Classes of Rock-forming Minerals4. Classes of Rock-forming Minerals
Mineral Chemical formula
Cleavage planesand number of
cleavage directionsSilicate
structure Specimen
1 plane Isolatedtetrahedra
Olivine (Mg, Fe)2SiO4
Mineral Chemical formula
Cleavage planesand number of
cleavage directionsSilicate
structure Specimen
1 plane Isolatedtetrahedra
2 planes at 90°Single chains
Olivine
Pyroxene
(Mg, Fe)2SiO4
(Mg, Fe)SiO3
Mineral Chemical formula
Cleavage planesand number of
cleavage directionsSilicate
structure Specimen
1 plane Isolatedtetrahedra
2 planes at 90°Single chains
2 planes at 60°and 120° Double chains
Olivine
Pyroxene
Amphibole
(Mg, Fe)2SiO4
(Mg, Fe)SiO3
Ca2(Mg, Fe)5Si8O22(OH)2
Mineral Chemical formula
Cleavage planesand number of
cleavage directionsSilicate
structure Specimen
1 plane Isolatedtetrahedra
2 planes at 90°Single chains
2 planes at 60°and 120° Double chains
1 plane Sheets
Olivine
Pyroxene
Amphibole
Micas
(Mg, Fe)2SiO4
(Mg, Fe)SiO3
Ca2(Mg, Fe)5Si8O22(OH)2
Muscovite:KAl2(AlSi3O10)(OH)2
Biotite:K(Mg, Fe)3AlSi3O10(OH)2
Mineral Chemical formula
Cleavage planesand number of
cleavage directionsSilicate
structure Specimen
1 plane Isolatedtetrahedra
2 planes at 90°Single chains
2 planes at 60°and 120° Double chains
1 plane Sheets
Olivine
Pyroxene
Amphibole
Micas
Feldspars
2 planes at 90° Three-dimensionalframework
(Mg, Fe)2SiO4
(Mg, Fe)SiO3
Ca2(Mg, Fe)5Si8O22(OH)2
Muscovite:KAl2(AlSi3O10)(OH)2
Biotite:K(Mg, Fe)3AlSi3O10(OH)2
Orthoclase feldspar:KAlSi3O8
Plagioclase feldspar: (Ca, Na) AlSi3O8
Thought questions for this chapterThought questions for this chapter
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
5. Physical Properties of Minerals5. Physical Properties of Minerals
Uses of physical properties:Uses of physical properties:
Mineral identificationMineral identification
Industrial application of Industrial application of mineralsminerals
5. Physical Properties of Minerals5. Physical Properties of Minerals
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
5. Physical Properties of Minerals5. Physical Properties of Minerals
5. Physical Properties of Minerals5. Physical Properties of Minerals
Hematite and Hematite and its streakits streak
Thought questions for this chapterThought questions for this chapter
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.
Thought questions for this chapterThought questions for this chapter
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
6. What Are Rocks?6. What Are Rocks?
Rocks are classified into three Rocks are classified into three groups:groups:
IgneousIgneous
SedimentarySedimentary
MetamorphicMetamorphic
6. What Are Rocks?6. What Are Rocks?
Igneous RocksIgneous Rocks
Sedimentary RocksSedimentary Rocks
Metamorphic RocksMetamorphic Rocks
Thought questions for this chapterThought questions for this chapter
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
7. The Rock Cycle7. The Rock Cycle
7. The Rock Cycle7. The Rock Cycle
7. The Rock Cycle7. The Rock Cycle
7. The Rock Cycle7. The Rock Cycle
7. The Rock Cycle7. The Rock Cycle
Thought questions for this chapterThought questions for this chapter
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
8. Concentrations of Valuable 8. Concentrations of Valuable Mineral ResourcesMineral Resources
Deformedcountry rock Geysers and
hot springs
Plutonicintrusion
MagmaMagma
GroundwaterGroundwater
Groundwater dissolves metal oxidesand sulfides. Heated by the magma, it rises, precipitating metal ores in joints.
Deformedcountry rock Geysers and
hot springs
Plutonicintrusion
MagmaMagma
GroundwaterGroundwater
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
8. Concentrations of Valuable 8. Concentrations of Valuable Mineral ResourcesMineral Resources
Open-pit mine for disseminated Open-pit mine for disseminated deposits of copper-bearing minerals.deposits of copper-bearing minerals.
8. Concentrations of Valuable 8. Concentrations of Valuable Mineral ResourcesMineral Resources
Igneous depositsIgneous deposits
Chromitelayers (dark)in layeredigneous rock
8. Concentrations of Valuable 8. Concentrations of Valuable Mineral ResourcesMineral Resources
Sedimentary deposits:Sedimentary deposits:
Copper, iron, other metalsCopper, iron, other metals
Gold, diamonds, other Gold, diamonds, other heavy minerals (placers)heavy minerals (placers)
8. Concentrations of Valuable 8. Concentrations of Valuable Mineral ResourcesMineral Resources
Thought questions for this chapterThought questions for this chapter
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
Key terms and conceptsKey terms and concepts
LusterLusterMagmaMagmaMetallic bondMetallic bondMetamorphic rockMetamorphic rockMineralMineralMineralogyMineralogyMohs scale of hardnessMohs scale of hardnessOreOreOxidesOxidesPolymorphPolymorphPrecipitatePrecipitateRegional metamorphismRegional metamorphismRockRockRock cycleRock cycle
Key terms and conceptsKey terms and concepts
SedimentSedimentSedimentary rockSedimentary rockSilicateSilicateSiliclastic sedimentsSiliclastic sedimentsSpecific gravitySpecific gravityStreakStreakSulfateSulfateSulfideSulfideTextureTextureTrace elementTrace elementVeinVeinWeatheringWeathering
Key terms and conceptsKey terms and concepts