MINERALOGY Some Common Minerals Illustrated by 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: –O47% –Si28% –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

Common Mineral Groups SulfidesS 2- OxidesO 2- Carbonates(CO 3 ) 2- Sulphates(SO 4 ) 2- Phosphates(PO 4 ) 3- HalidesF,Cl, etc. Native elementsAu, Cu, C, etc. Silicates(SiO 4 ) 4-

SULFIDES PyriteChalcopyriteGalena FeS 2 (Cu,Fe)S 2 PbS Sphalerite (Zn,Fe)S

OXIDES HematiteLimoniteMagnetite –Fe 2 O 3 Fe 2 O 3  nH2OFe 3 O 4 Corundum –Al 2 O 3

CARBONATES Double refraction in Calcite CaCO 3 Dolomite crystals ( Ca,Mg)CO 3 Siderite FeCO 3

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 CaSO 4  nH2O Anhydrite CaSO 4

PHOSPHATES Apatite Ca 3 (PO 4 ) 2

HALIDES Fluorite CaF 2 4 cleavages Halite NaCl 3 cleavages at right angles

NATIVE ELEMENTS SulphurS 8 GoldAu tiny nuggets panned at Ovens, Nova Scotia GraphiteC DiamondC