MINERALOGYSome Common Minerals

Illustratedby Charina Cameron

Mineral Groups• Nearly 4000 minerals• Only a few dozen are abundant in Earth’s crust• These are the rock-forming minerals• 8 elements comprise the bulk of these minerals• They also represent 98% of the continental crust:

– O 47%– Si 28%– Al 8%– Fe 5%– Ca 4%– Na 3%– K 3%– Mg 2%

Silicate minerals

Major Properties of Minerals• Crystal form• Luster (metallic, non-metallic, etc.)• Colour (often due to impurities)• Streak (colour of powder)• Hardness (Moh’s scale: 1 to 10)• Cleavage

– none or up to 6 surfaces– planes of weakness in crystal structure

• Fracture (conchoidal, etc.)• Specific gravity

– density compared to water– galena is much greater than quartz (2.65)

Special Mineral Properties• Magnetic• Elastic• malleable• taste• smell• feel

– Soapy– Greasy

• Double refraction• Reaction to HCl

Moh’s HARDNESS SCALE

Talc

Gypsum

Calcite

Fluorite

Apatite

Orthoclase

Quartz

Topaz

Corundum

Diamond

1

2

3

4

5

6

7

8

9

10

Common Mineral Groups• Sulfides S2-

• Oxides O2-

• Carbonates (CO3)2-

• Sulphates (SO4)2-

• Phosphates (PO4)3-

• Halides F,Cl, etc.• Native elements Au, Cu, C, etc.• Silicates (SiO4)4-

SULFIDES

• Pyrite Chalcopyrite Galena• FeS2 (Cu,Fe)S2 PbS

• Sphalerite• (Zn,Fe)S

OXIDES

• Hematite Limonite Magnetite– Fe2O3 Fe2O3 nH2O Fe3O4

• Corundum– Al2O3

CARBONATES• Double refraction in Calcite

CaCO3

• Dolomite crystals (Ca,Mg)CO3

• Siderite• FeCO3

CARBONATES• Calcite crystals from a vein in Wolfville Formation,

showing 3 perfect cleavages not at right angles

CARBONATES• Hexagonal Calcite crystals from Scots Bay Fm

SULPHATES• Gypsum

CaSO4nH2O

• Anhydrite CaSO4

PHOSPHATES• Apatite

Ca3(PO4)2

HALIDES• Fluorite

CaF2

4 cleavages

• HaliteNaCl3 cleavages

at right angles

NATIVE ELEMENTS• Sulphur S8

• Gold Autiny nuggets panned at Ovens, Nova Scotia

• Graphite C

• Diamond C