Minerals: The Building Blocks of Rocks. I.Definition II. Formation III. Properties IV. Classification.

Minerals: The Building Blocks of Rocks

I. Definition

II. Formation

III. Properties

IV. Classification

I. Definition of a Mineral

A. naturally occurringCannot be human made

B. inorganicCannot contain organic material

C. orderly internal arrangement of atoms (solid)Crystalline structure

D. definite chemical compositionDefines the mineral (e.g. Fe2O3 = hematite, whereas Fe3O4 = magnetite)

I. Definition

II. Formation

III. Properties

IV. Classification

II. Formation of Minerals

A. Process called crystallization

B. Igneous1. Magma = large crystals (beneath surface)2. Lava = small crystals (above surface)

C. Solutions1. 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 structure2. planar surfaces are called crystal faces3. 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 weakness2. Described by:

a. Number of planesb. 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

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• 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 fracture2. Types

a. Conchoidal- smooth curve, bowl-shapedb. Hackly- sharp, jagged edgesc. Uneven- rough and irregulard. 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 light2. Two major types:

a. Metallic lusterb. Non-metallic luster

Metallicexample

Non-metallicexample

E. Color:1. Most obvious, but often misleading2. Different colors result from impurities

Example:fluorite

F. Streak:1. Color of a mineral in powdered form2. Obtained by scratching a mineral on an

unglazed porcelain plate

Example:Hematite

G. Hardness:1. The resistance of a mineral to scratching2. Mohs Scale of Hardness

a. Developed by Friedrick Mohs, 1812b. relative scalec. 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 mineral2. metallic minerals tend to have higher

densities than non-metallic mineralsGalenaD=7.5

QuartzD=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

C. Groups

1. Native elementsa. Natural element in pure formb. Examples:

1. Copper, Cu2. Gold, Au3. Silver, Ag

C. Groups

2. Halidesa. Formed from halogen ions (F-, Cl-, Br-, etc.)b. Examples:

1. Halite, NaCl2. Fluorite, CaF2

C. Groups

3. Sulfidesa. Formed from sulfur ion (S2-)b. Examples:

1. Galena, PbS2. Pyrite, FeS2 3. Cinnabar, HgS4. Sphalerite, ZnS

C. Groups

4. Oxidesa. Formed from oxygen ion (O2-)b. Examples:

1. Hematite, Fe2O3

2. Corundum, Al2O3

3. Chromite, FeCr2O4

C. Groups

5. Carbonatea. Formed from carbonate ion (CO3

2-)b. Examples:

1. Calcite, CaCO3

2. Magnesite, MgCO3

3. Rhodochrosite, MnCO3

C. Groups

6. Sulfatea. Formed from sulfate ion (SO4

2-)b. Examples:

1. Barite, BaSO4

2. Celestite, SrSO4

C. Groups

7. Silicatesa. Formed from silicate ion b. Most common rock-forming mineralsc. Most complex (have varying Si/O

ratios)d. Examples:

1. Quartz, SiO2

2. Enstatite, MgSiO3

3. Benitoite, BaTi(Si3O9)- California’s state mineral