_Mineral_ _Composition_ _Specific Gravity_ _Hardness_ Albite NaAlSi₃O₈ 2.62 6 Almandite Fe₃Al₂ (SiO₄)₂ 4.2 7 Amphibole Ca₂Mg₅Si₈O₂₂(OH)₂ 3.0-3.3 1-2½ asbestos Anhydrite CaSO₄ 2.9 3-3½ Argentite Ag₂S 7.3 2-2½ Azurite Cu₃(CO₃)₂(OH)₂ 3.77 3½-4 Barite BaSO₄ 4.5 3-3½ Biotite K(Mg, 2.8-3.2 2½-3 Fe)₃AlSi₃O₁₀(OH)₂ Braunite 3MnMnO₃MnSiO₃ 4.75-4.82 6-6½ Calcite CaCO₃ 2.72 3 Carnotite K₂O·2UO₃·V₂O₅·nH₂O 5.03 2 Cassiterite SnO₂ 6.8-7.1 6-7 Celestite SrSO₄ 3.95-3.97 3-3½ Cerargyrite AgCl 5.5 1-1½ Chalcocite Cu₂S 5.5-5.8 2½-3 Chalcopyrite CuFeS₂ 4.1-4.3 3½-4 Cinnabar HgS 8.10 2½ Dolomite CaMg(CO₃)₂ 2.85 3½-4 Feldspar (_see_ Albite, Microcline, Orthoclase) Fluorite CaF₂ 3.18 4 Galena PbS 7.4-7.6 2½ Garnet (_see_ Almandite, Grossularite) Gold Au 15.0-19.3 2½-3 Graphite C 2.2 1-2 Grossularite Ca₃Al₂(SiO₄)₃ 3.53 6½ Gypsum CaSO₄·2H₂O 2.32 2 Halite NaCl 2.16 2½ Hematite Fe₂O₃ 5.26 1-6½ Hollandite MnBaMn₁₆O₁₄ 4.7-5 4-6 Limonite FeO(OH)·nH₂O 3.6-4.0 1-5½ Magnetite Fe₃O₄ 5.18 6 Malachite Cu₂CO₃(OH)₂ 3.9-4.03 3½-4 Mica (_see_ Muscovite, Biotite) Microcline KAlSi₃O₈ 2.54-2.57 6 Muscovite KAl₃Si₃O₁₀(OH)₂ 2.76-3.1 2-2½ Opal SiO₂·nH₂O 1.9-2.2 5-6 Orthoclase KAlSi₃O₈ 2.57 6 Pitchblende UO₂ 6.5-8.5 5½ Pyrite FeS₂ 5.02 6-6½ Pyrolusite MnO₂ 4.75 1-2 Quartz SiO₂ 2.65 7 Serpentine Mg₃Si₂O₅(OH)₄ 2.48 3-4 Silver Ag 10.5 2½-3 Sulfur S 2.05-2.09 1½-2½ Talc Mg₃Si₄O₁₀(OH)₂ 2.7-2.8 1 Topaz Al₂SiO₄(F,OH)₂ 3.4-3.6 8