Minerals: The Building Blocks of Rocks

I.Definition II. Formation III. Properties IV. Classification

I. Definition of a Mineral A.naturally occurring Cannot be human made B.inorganic Cannot contain organic material C.orderly internal arrangement of atoms (solid) Crystalline structure D.definite chemical composition Defines the mineral (e.g. Fe 2 O 3 = hematite, whereas Fe 3 O 4 = magnetite)

I.Definition II. Formation III. Properties IV. Classification

II. Formation of Minerals A.Process called crystallization B.Igneous 1.Magma = large crystals (beneath surface) 2.Lava = small crystals (above surface) C.Solutions 1.Precipitation- water evaporates leaving behind salts (surface) 2.Deposition- minerals are deposited from hydrothermal systems (beneath surface- veins)

I.Definition II. Formation III. Properties IV. Classification

A. Crystal Form (or shape): 1.external expression of a mineral’s internal atomic structure 2.planar surfaces are called crystal faces 3.angles between crystal faces are constant for any particular mineral Quartz Pyrite III. Properties of Minerals

B. Cleavage: 1.The tendency of a mineral to break along planes of weakness 2.Described by: a.Number of planes b.Angles between adjacent planes Do not confuse cleavage planes with crystal faces! Crystal faces are just on the surface and may not repeat when the mineral is broken. constant for each mineral }

Cleavage (1 direction): Example: mica

Cleavage (2 directions): orthoclase amphibole

Cleavage (3 directions): halite calcite

Cleavage (4 directions): fluorite

C. Fracture: 1.Minerals that do not exhibit cleavage are said to fracture 2.Types a.Conchoidal- smooth curve, bowl-shaped b.Hackly- sharp, jagged edges c.Uneven- rough and irregular d.Fibrous- shows fibers or splinters

Conchoidal fracture (quartz)

Hackly fracture (copper)

Uneven fracture (limonite)

Fibrous fracture (chrysotile)

D. Luster: 1.How a mineral surface reflects light 2.Two major types: a.Metallic luster b.Non-metallic luster Metallic example Non-metallic example

E. Color: 1.Most obvious, but often misleading 2.Different colors result from impurities Example: fluorite

F. Streak: 1.Color of a mineral in powdered form 2.Obtained by scratching a mineral on an unglazed porcelain plate Example: Hematite

G. Hardness: 1.The resistance of a mineral to scratching 2.Mohs Scale of Hardness a.Developed by Friedrick Mohs, 1812 b.relative scale c.consists of 10 minerals, ranked 1 (softest) to 10 (hardest)

Mohs Hardness Scale Hardest (10) – Diamond Softest (1) – Talc Common objects: - Fingernail (2.5) - Copper penny (3.5) - Wire nail (4.5) - Glass (5.5) - Streak plate (6.5)

H. Density: 1.mass of a mineral divided by volume of the mineral 2.metallic minerals tend to have higher densities than non-metallic minerals Galena D=7.5 Quartz D=2.65

I.Distinctive properties: 1.taste (halite tastes salty) 2.feel (talc feels soapy, graphite feels greasy) 3.smell (sulfur smells like rotten eggs) 4.magnetism (magnetite attracts a magnet) 5.double refraction (calcite when placed over printed material, letters appear doubled) 6.reaction with hydrochloric acid (calcite fizzes)

I.Definition II. Formation III. Properties IV. Classification

III. Classification of Minerals A.Classified based on chemical composition B.Most minerals contain only eight elements

III. Classification of Minerals A.Classified based on chemical composition B.Most minerals contain only eight elements C.Groups

1. Native elements a. Natural element in pure form b. Examples: 1. Copper, Cu 2. Gold, Au 3. Silver, Ag

C. Groups 2. Halides a. Formed from halogen ions (F -, Cl -, Br -, etc.) b. Examples: 1. Halite, NaCl 2. Fluorite, CaF 2

C. Groups 3. Sulfides a. Formed from sulfur ion (S 2- ) b. Examples: 1. Galena, PbS 2. Pyrite, FeS 2 3. Cinnabar, HgS 4. Sphalerite, ZnS

C. Groups 4. Oxides a. Formed from oxygen ion (O 2- ) b. Examples: 1. Hematite, Fe 2 O 3 2. Corundum, Al 2 O 3 3. Chromite, FeCr 2 O 4

C. Groups 5. Carbonate a. Formed from carbonate ion (CO 3 2- ) b. Examples: 1. Calcite, CaCO 3 2. Magnesite, MgCO 3 3. Rhodochrosite, MnCO 3

C. Groups 6. Sulfate a. Formed from sulfate ion (SO 4 2- ) b. Examples: 1. Barite, BaSO 4 2. Celestite, SrSO 4

C. Groups 7. Silicates a.Formed from silicate ion b.Most common rock-forming minerals c.Most complex (have varying Si/O ratios) d.Examples: 1.Quartz, SiO 2 2.Enstatite, MgSiO 3 3.Benitoite, BaTi(Si 3 O 9 )- California’s state mineral