Mineral Tables - Minerals and Their Properties ( cont.) Mineral Hardness Cleavage Other properties Importance Composition Fracture Arsenopyrite 5.5 - 6 2 fair Silvery to steel gray; dark Occurs with ores cleavages gray to black streak Pyrite (FeS2) 6 - 6.5 uneven to Brassy-yellow; may tarnish Occurs with ores conchoidal iridescent; streak greenish to brownish black; crystals are cubes Talc (Mg, OH 1 1 perfect Pearly lustre; white, pale Talcum powder mica) cleavage green, tan or gray in colour, soapy feel Kaolinite (Al, OH 1 not visible Earthy lustre; white to tan Major mica) colour; earthy odor; component of extremely fine-grained clay Vermiculite (Mg, 1.5 1 perfect Yellow to brown; pearly Insulation and OH, H2O mica) cleavage lustre; expands greatly potting soil when heated Gypsum 2 1 good Glassy to pearly crystals; Plaster, (CaSO4.H2O) cleavage aggregates are dull, wallboard, paper silky or fibrous; pale colours Cinnabar (HgS) 2 - 2.5 not visible Red to brownish colour, Source of scarlet or orange-red mercury streak; earthy or fine crystals Chlorite (Mg, Fe, 2 - 2.5 1 perfect Pale to dark green; pearly Rock-forming Al OH mica) cleavage to greasy mineral Muscovite (K, Al 2.5 1 perfect Pearly to glassy lustre; Common rock ,OH mica) cleavage sheets flexible and elastic; forming mineral colourless to pale tints Biotite (K, Mg, Fe, 2.5 1 perfect Pearly to glassy lustre; Common rock Al mica) cleavage sheets flexible and elastic; forming mineral dark amber to black Serpentine (Mg, 2 - 4 not visible Greasy yellow to greenish Source of OH Silicate) black; may be silky or asbestos fibrous (asbestos form) Halite (NaCl) 2.5 3 good Glassy to greasy; pale salt cleavages at colours; salty taste 90o
Mineral Tables - Minerals and Their Properties ( cont.) Mineral Composition Hardness Cleavage Fracture Other properties Importance Arsenopyrite 5.5 - 6 2 fair cleavages Silvery to steel gray; dark gray to black streak Occurs with ores Pyrite (FeS2) 6 - 6.5 uneven to conchoidal Brassy-yellow; may tarnish iridescent; streak greenish to brownish black; crystals are cubes Occurs with ores Talc (Mg, OH mica) 1 1 perfect cleavage Pearly lustre; white, pale green, tan or gray in colour, soapy feel Talcum powder Kaolinite (Al, OH mica) 1 not visible Earthy lustre; white to tan colour; earthy odor; extremely fine-grained Major component of clay Vermiculite (Mg, OH, H2O mica) 1.5 1 perfect cleavage Yellow to brown; pearly lustre; expands greatly when heated Insulation and potting soil Gypsum (CaSO4.H2O) 2 1 good cleavage Glassy to pearly crystals; aggregates are dull, silky or fibrous; pale colours Plaster, wallboard, paper Cinnabar (HgS) 2 - 2.5 not visible Red to brownish colour, scarlet or orange-red streak; earthy or fine crystals Source of mercury Chlorite (Mg, Fe, Al OH mica) 2 - 2.5 1 perfect cleavage Pale to dark green; pearly to greasy Rock-forming mineral Muscovite (K, Al ,OH mica) 2.5 1 perfect cleavage Pearly to glassy lustre; sheets flexible and elastic; colourless to pale tints Common rock forming mineral Biotite (K, Mg, Fe, Al mica) 2.5 1 perfect cleavage Pearly to glassy lustre; sheets flexible and elastic; dark amber to black Common rock forming mineral Serpentine (Mg, OH Silicate) 2 - 4 not visible Greasy yellow to greenish black; may be silky or fibrous (asbestos form) Source of asbestos Halite (NaCl) 2.5 3 good cleavages at 90o Glassy to greasy; pale colours; salty taste salt