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1. Minerals and
Rocks

2. Lecture Outline
 What are minerals?
 Common rock-forming minerals
 Physical properties of minerals
 Basic rock types
 The rock cycle

3. Minerals
 Natural
 Solid
 Atoms arranged in orderly repeating 3D array:
crystalline
 Not part of the tissue of an organism
 Composition fixed or varies within defined limits
Minerals are the “building blocks” of rock
A mineral is a naturally occurring, solid
crystalline substance, generally inorganic,
with a specific chemical composition

4. Large individual crystals (rare)
Mass of small grains: each is a crystal,
but grown up against each other

5. Atomic Structure of Minerals
 NaCl - sodium chloride
Halite

6. Chemical Bonds: Ionic
 Electrical attraction between ions of opposite charge
 Bond strength increases with the electrical charges of the
ions
 Bond strength decreases as the distance between the
ions increases
 Most minerals are this kind of compound

7. Na+
Cl-
Ionic Bonding example:
halite
Anion
Cation

8. Covalent Bonds:
 Electron sharing
 Generally stronger than ionic bonds (e.g., diamond)

9. Crystallization of Minerals
 Need starting material with atoms that can come
together in the proper proportions
 Growth from a liquid or a gas
 Time and space for crystallization
 Appropriate temperature and pressure
 Examples
 Magma that has cooled below its melting point
 Supersaturated solution --> precipitation

10. Crystallization of Minerals
 Crystals begin as an initial “seed” - a microscopic
crystal
 Atoms keep being added in a 3D array, repeating the
basic arrangement
 Crystal faces are based on the array structure

11. Cations and Anions
 Anions are typically large
 Cations are relatively small
 Crystal structure is
determined largely by the
arrangement of the anions

12. Common cations and anions
Radii given in angstroms; 10-8 cm

13. Ions can be compound
 So far, we’ve talked about individual atomic ions
 Many common minerals are silicates
SiO4
4-
Complex ions act
as a single ion in
forming crystal
structure

14. Cation Substitution
 Crystal structure determined by those large anions
 Various cations can substitute for each other in many
minerals
 Same crystal structure
 Different chemical composition

16. Polymorphs
 Minerals with the same composition, but different
crystal structure.

17. Common Rock-Forming Minerals
Minerals fall into a small number of related “families” based
mainly on the anion in them

18. Silicates
 Most abundant minerals in the Earth's crust
 Silicate ion (tetrahedron), SiO4
4-
 Quartz (SiO2), K-feldspar (KAlSi3O8), olivine
((Mg, Fe)2SiO4), kaolinite (Al2Si2O5(OH)4)

19. Quartz (SiO2)

20. Silicate structure
 Most of the most common rocks in the crust are silicates
 Silicate tetrahedra can combine in several ways to form
many common minerals
 Typical cations:
K+, Ca+, Na+, Mg2+, Al3+, Fe2+

21. Different numbers of oxygen ions are shared among tetrahedra

22. Carbonates
 Cations with carbonate ion (CO3
2-)
 Calcite (CaCO3), dolomite (CaMg(CO3)2), siderite
(FeCO3), smithsonite (ZnCO3)
 Make up many common rocks including limestone and
marble
 Very important for CCS!

23. Calcite (CaCO3)

24. CaCO3 + 2H+ = Ca2+ + CO2 + H2O

25. Smithsonite (ZnCO3)

26. Oxides
 Compounds of metallic cations and oxygen
 Important for many metal ores needed to make things
(e.g., iron, chromium, titanium)
 Ores are economically useful (i.e., possible to mine)
mineral deposits

27. Hematite (Fe2O3)

28. Sulfides
 Metallic cations with sulfide (S2-) ion
 Important for ores of copper, zinc, nickel, lead, iron
 Pyrite (FeS2), galena (PbS)

29. Galena (PbS)

31. Sulfates
 Minerals with sulfate ion (SO4
2-)
 Gypsum (CaSO4
.H2O), anhydrite (CaSO4)

32. Gypsum

33. Cave of the Crystals
•1,000 feet depth in the silver
and lead Naica Mine
•150 degrees, with 100 %
humidity
•4-ft diameter columns 50 ft
length
Gypsum

34. Identification of Minerals
 Chemical composition (microprobes and wet chemical
methods)
 Crystal structure (X-ray diffraction)
 Physical properties

35. Physical properties
 Hardness

37. Physical properties
 Hardness
 Cleavage: tendency of minerals to break along flat
planar surfaces into geometries that are determined
by their crystal structure

38. Cleavage in mica

39. Cleavage in calcite

40. Halite (NaCl)

41. Physical properties
 Hardness
 Cleavage
 Fracture: tendency to break along other surfaces
(not cleavage planes)

42. Conchoidal fractures

43. Physical properties
 Hardness
 Cleavage
 Fracture
 Luster (metallic, vitreous, resinous, earthy, etc.)
 Color (often a poor indicator; streak color is better)
 Specific gravity
 Crystal habit (shape)

44. Rocks
An aggregate of one or more minerals; or a body of
undifferentiated mineral matter (e.g., obsidian); or of
solid organic matter (e.g., coal)
 More than one crystal
 Volcanic glass
 Solidified organic matter
 Appearance controlled by composition and size and
arrangement of aggregate grains (texture)

45. RockTypes
 Igneous
 Form by solidification of molten rock (magma)
 Sedimentary
 Form by lithification of sediment (sand, silt, clay,
shells)
 Metamorphic
 Form by transformations of preexisting rocks (in
the solid state)

46. Igneous Rocks
 Intrusive
 Extrusive

47. Intrusive (plutonic)
 Form within the Earth
 Slow cooling
 Interlocking large crystals
 Example = granite

49. Extrusive (volcanic)
 Form on the surface of the Earth as a result of volcanic
eruption
 Rapid cooling
 Glassy and/or fine-grained texture
 Example = basalt

50. Basalt: igneous extrusive

51. Intrusive and extrusive igneous rocks

52. Sedimentary Rocks

53. Origin of sediment
 Produced by weathering and erosion or by
precipitation from solution
 Weathering = chemical and mechanical breakdown of
rocks
 Erosion = processes that get the weathered material
moving

54. Sediment types
 Clastic sediments are derived from the physical
deposition of particles produced by weathering and
erosion of preexisting rock.
 Chemical and biochemical sediments are precipitated
from solution.

55. Clastic
Chemical/biochemical

56. Lithification
 The process that converts sediments into solid rock
 Compaction
 Cementation

57. Cemented sandstone

59. Metamorphic Rocks

60. Regional and contact metamorphism

61. conglomerate
metaconglomerate

62. granite
gneiss

67. The Rock
Cycle

68. The Rock Cycle