1. Understanding Earth Chapter 3: EARTH MATERIALS Minerals and Rocks
Grotzinger • Jordan
Understanding Earth
Sixth Edition
Chapter 3:
EARTH MATERIALS
Minerals and Rocks
© 2011 by W. H. Freeman and Company

2. Chapter 3:
Earth Materials:
Minerals and Rocks

3. About Earth Materials
All Earth materials are composed of atoms bound together.
Minerals are composed of atoms bonded together and are the building blocks of rocks.
Rocks are composed of minerals and they record various geologic processes.

4. Lecture Outline What are minerals? 2. The structure of matter
3. The formation of minerals
4. Classes of rock-forming minerals
5. Physical properties of minerals
6. What are rocks?

5. Lecture Outline
7. The rock cycle: interactions between the plate tectonic and climate systems
8. Concentrations of valuable mineral resources

6. Minerals are the building blocks of rocks.
1. What Are Minerals?
Minerals are the building blocks of rocks.

7. What Are Minerals?
Geologists define mineral as a naturally occurring, solid, crystalline substance, usually inorganic, with a specific chemical composition.

8. Naturally occurring = found in nature
What Are Minerals?
Naturally occurring = found in nature
Solid, crystalline substance = atoms are arranged in orderly patterns
Usually inorganic = not a product of living tissue
With a specific chemical formula = unique chemical composition

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

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

11. Atomic nucleus: protons and neutrons.
2. The Structure of Matter
Atomic nucleus: protons and neutrons.
Electrons: cloud of moving particles surrounding the nucleus.
Example: the carbon atom (C)

12. The Carbon Atom
electron cloud
atomic nucleus

13. The Carbon Atom
electron cloud
atomic nucleus
carbon has 6
electrons…

14. The Carbon Atom electron cloud atomic nucleus carbon has 6 electrons…
proton (+)
neutron

15. The Carbon Atom electron cloud atomic nucleus carbon has 6 electrons…
…and a nucleus
of 6 protons …
electron (–)
proton (+)
neutron

16. The Carbon Atom electron cloud atomic nucleus Carbon has 6 electrons…
…and a nucleus
of 6 protons …
…and 6 neutrons having no charge.
electron (–)
proton (+)
neutron

17. 2. The Structure of Matter
Isotopes – atoms of the same element with different numbers of protons.
Example: the carbon atom (C) typically has 6 neutrons and 6 protons (called C12), but there are also small amounts of C13 and C14.

18. Example: H + H + O = H2O Example: Na + Cl = NaCl
2. The Structure of Matter
Chemical reactions – interactions of the atoms of two or more elements in certain fixed proportions.
Example: H + H + O = H2O
Example: Na + Cl = NaCl

19. Chemical compounds that are minerals form by: electron sharing or
2. The Structure of Matter
Chemical compounds that are minerals form by:
electron sharing or
electron transfer

20. Carbon atoms in a diamond
Electron Sharing:
Carbon atoms in a diamond

21. Sodium (Na) + chlorine (Cl) =
Electron Transfer:
Sodium (Na) + chlorine (Cl) =
NaCl (halite)

22. Sodium (Na) + chlorine (Cl) =
Electron Transfer:
Sodium (Na) + chlorine (Cl) =
NaCl (halite)
Each sodium ion (circled in red)
is surrounded by 6 chloride ions
(circled in yellow), and vice versa.

23. in the proper proportion and proper arrangement
3. The Structure of Minerals
How do minerals form?
Crystallization –
atoms come together
in the proper proportion
and proper arrangement

24. Electrical charges of atomic ions Cation – positively charged
3. The Structure of Minerals
Electrical charges of atomic ions
Cation – positively charged
Anion – negatively charged
Atomic ions arrange themselves according to charge and size.

25. 3. The Structure of Minerals
The forces of electrical attraction between protons (+) and electrons (-) that hold minerals and other chemical compounds together
covalent bonds
ionic bonds
metallic bonds

26. 3. The Structure of Minerals

27. During cooling of molten rock During evaporation of water
3. The Structure of Minerals
When do minerals form?
During cooling of molten rock
During evaporation of water
Upon changes in temperature and pressure on existing minerals

28. Chemical classes of minerals:
4. Classes of Rock-forming Minerals
Chemical classes of minerals:
Silicates – contain O and Si
Carbonates – contain C and O
Oxides – contain O and metallic cations
Sulfides – contain S and metallic cations
Sulfates – contain SO4 and metallic cations

29. Chemical classes (cont.): Halides – contain Cl, F, I, or Br
4. Classes of Rock-forming Minerals
Chemical classes (cont.):
Halides – contain Cl, F, I, or Br
Hydroxides – contain OH
Native elements – masses of all the same element metallically bonded

30. 4. Classes of Rock-forming Minerals
Formation of silicate minerals
Silicate ion (SiO44–)
Oxygen ions
(O2–)
Silicon ion
(Si4+)

31. Silicate ion (SiO44–)
The silicate
ion forms
tetrahedra.
Oxygen ions
(O2–)
Silicon ion
(Si4+)

32. Quartz
structure
Silicate ion (SiO44–)
The silicate
ion forms
tetrahedra.
Oxygen ions
(O2–)
Silicon ion
(Si4+)

33. Quartz
structure
Quartz is
a silicate
polymorph.
Silicate ion (SiO44–)
The silicate
ion forms
tetrahedra.
Oxygen ions
(O2–)
Silicon ion
(Si4+)

34. Quartz
structure
Silicate ion (SiO44–)
The silicate
ion forms
tetrahedra.
Oxygen ions
(O2–)
Silicon ion
(Si4+)
Tetrahedra are the basic building blocks of all silicate minerals. About 95% of Earth’s minerals are silicates.

35. Thought questions for this chapter
Draw a simple diagram to show how silicon and oxygen in silicate minerals share electrons.

36. Types of silicate minerals: Isolated silica tetrahedra
4. Classes of Rock-forming Minerals
Types of silicate minerals:
Isolated silica tetrahedra
Single-chain linkages
Double-chain linkages
Sheet linkages
Frameworks

37. Cleavage planes
and number of
cleavage directions
Silicate
structure
Mineral
Chemical formula
Specimen
1 plane
Isolated
tetrahedra
Olivine
(Mg, Fe)2SiO4

38. Cleavage planes
and number of
cleavage directions
Silicate
structure
Mineral
Chemical formula
Specimen
1 plane
Isolated
tetrahedra
Olivine
(Mg, Fe)2SiO4
2 planes at 90°
Single chains
Pyroxene
(Mg, Fe)SiO3

39. Cleavage planes
and number of
cleavage directions
Silicate
structure
Mineral
Chemical formula
Specimen
1 plane
Isolated
tetrahedra
Olivine
(Mg, Fe)2SiO4
2 planes at 90°
Single chains
Pyroxene
(Mg, Fe)SiO3
2 planes at 60°
and 120°
Double chains
Amphibole
Ca2(Mg, Fe)5Si8O22(OH)2

40. Cleavage planes
and number of
cleavage directions
Silicate
structure
Mineral
Chemical formula
Specimen
1 plane
Isolated
tetrahedra
Olivine
(Mg, Fe)2SiO4
2 planes at 90°
Single chains
Pyroxene
(Mg, Fe)SiO3
2 planes at 60°
and 120°
Double chains
Amphibole
Ca2(Mg, Fe)5Si8O22(OH)2
1 plane
Sheets
Muscovite:
KAl2(AlSi3O10)(OH)2
Micas
Biotite:
K(Mg, Fe)3AlSi3O10(OH)2

41. Cleavage planes
and number of
cleavage directions
Silicate
structure
Mineral
Chemical formula
Specimen
1 plane
Isolated
tetrahedra
Olivine
(Mg, Fe)2SiO4
2 planes at 90°
Single chains
Pyroxene
(Mg, Fe)SiO3
2 planes at 60°
and 120°
Double chains
Amphibole
Ca2(Mg, Fe)5Si8O22(OH)2
1 plane
Sheets
Muscovite:
KAl2(AlSi3O10)(OH)2
Micas
Biotite:
K(Mg, Fe)3AlSi3O10(OH)2
2 planes at 90°
Three-dimensional
framework
Orthoclase feldspar:
KAlSi3O8
Feldspars
Plagioclase feldspar:
(Ca, Na) AlSi3O8

42. Thought questions for this chapter
Diopside, a pyroxene, has the formula (Ca, Mg)2Si2O6. What does that tell you about its crystal structure and cation substitution?
What physical properties of sheet silicates are related to
their crystal structure?

43. Hardness 5. Physical Properties of Minerals Cleavage Fracture Luster
Color
Streak
Density
Crystal habit

46. Uses of physical properties: Mineral identification
5. Physical Properties of Minerals
Uses of physical properties:
Mineral identification
Industrial application of minerals

47. 5. Physical Properties of Minerals
Mica and its
cleavage

48. 5. Physical Properties of Minerals
Pyrite and
its crystal
habit

49. 5. Physical Properties of Minerals
Calcite and its
cleavage

50. 5. Physical Properties of Minerals

51. 5. Physical Properties of Minerals
Hematite and
its streak

52. Thought questions for this chapter
Aragonite, with a density of 2.9 g/cm3, has exactly the
same chemical composition as calcite, which has a
density of 2.7 g/cm3. Other things being equal, which of
these two minerals is more likely to have formed under
high pressure?
There are at least seven physical properties one can
use to identify an unknown mineral. Which ones are most useful in discriminating between minerals that look similar? Describe a strategy that would allow you to prove that an unknown clear calcite crystal is not the same mineral as a known clear crystal of quartz.

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

54. Identity is determined by: texture composition
6. What Are Rocks?
Rocks are naturally occurring solid aggregates of minerals, or in some cases, non-mineral solid matter.
Identity is determined by:
texture
composition

55. Rocks are classified into three groups:
6. What Are Rocks?
Rocks are classified into three groups:
Igneous
Sedimentary
Metamorphic

56. 6. What Are Rocks?

58. Igneous Rocks

60. Sedimentary Rocks

61. Metamorphic Rocks

62. Thought questions for this chapter
In some bodies of granite, we can find very large crystals, some as much as a meter across, yet these crystals tend to have few crystal faces. What can you deduce about the conditions under which these large crystals grew?
Which igneous intrusion would you expect to have a wider contact metamorphic zone: one intruded by a very hot magma or one intruded by a cooler magma?
Where are igneous rocks most likely to be found? How could you be certain that the rocks were igneous and not sedimentary or metamorphic?

63. Interactions between the plate tectonic and climate systems
7. The Rock Cycle
Interactions between the plate tectonic and climate systems

64. 7. The Rock Cycle

65. 7. The Rock Cycle

66. 7. The Rock Cycle

67. 7. The Rock Cycle

68. 7. The Rock Cycle

69. 7. The Rock Cycle

70. Thought questions for this chapter
What geologic processes transform a sedimentary rock into an igneous rock?
Describe the geologic processes by which an igneous rock is transformed into a metamorphic rock and then exposed to erosion.
Using the rock cycle, trace the path from a magma to a granitic intrusion to a metamorphic gneiss to a sandstone. Be sure to include the roles of the plate tectonics climate systems and the specific processes that create rocks.

71. 8. Concentrations of Valuable
Mineral Resources
Types of ore minerals:
Vein deposits
Disseminated deposits
Igneous deposits
Sedimentary deposits

72. 8. Concentrations of Valuable
Mineral Resources
Deformed
country rock
Geysers and
hot springs
Origin of vein deposits
Groundwater
Magma
Plutonic
intrusion

73. Groundwater dissolves metal oxides
and sulfides. Heated by the magma, it
rises, precipitating metal ores in joints.
Deformed
country rock
Geysers and
hot springs
Groundwater
Magma
Plutonic
intrusion

74. Groundwater dissolves metal oxides
and sulfides. Heated by the magma, it
rises, precipitating metal ores in joints.
Deformed
country rock
Geysers and
hot springs
Vein deposit
Groundwater
Magma
Plutonic
intrusion

75. 8. Concentrations of Valuable
Mineral Resources
Typical sulfide minerals from vein deposits

76. 8. Concentrations of Valuable
Mineral Resources
Open-pit mine for disseminated
deposits of copper-bearing minerals.

77. 8. Concentrations of Valuable
Mineral Resources
Igneous deposits
Chromite
layers (dark)
in layered
igneous rock

78. 8. Concentrations of Valuable
Mineral Resources
Sedimentary deposits:
Copper, iron, other metals
Gold, diamonds, other heavy minerals (placers)

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

80. Key terms and concepts Atomic mass Atomic number Bedding
Anion
Atomic mass
Atomic number
Bedding
Biological sediment
Carbonate
Cation
Chemical sediments
Cleavage
Color
Contact metamorphism
Covalent bond
Crystal
Crystal habit

81. Key terms and concepts Disseminated deposit Electron sharing
Density
Disseminated deposit
Electron sharing
Electron transfer
Erosion
Fracture
Grain
Hardness
Hydrothermal solution
Igneous rock
Ion
Ionic bond
Isotope
Lithification

82. Key terms and concepts Magma Metallic bond Metamorphic rock Mineral
Luster
Magma
Metallic bond
Metamorphic rock
Mineral
Mineralogy
Mohs scale of hardness
Ore
Oxides
Polymorph
Precipitate
Regional metamorphism
Rock
Rock cycle

83. Key terms and concepts Sedimentary rock Silicate Specific gravity
Siliclastic sediments
Specific gravity
Streak
Sulfate
Sulfide
Texture
Trace element
Vein
Weathering