Page 236 - A Practical Introduction to Optical Mineralogy

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Appendix C Properties of ore
minerals

Mineral Formula - R % Colour - VHN Anisotropy Distinguished properties/resemblance See
range (associations) page
acanthite Ag,S 30-31 light grey 20-60 distinct twin lamellae
low temp. polymorph (greenish) (Pb-Sb-As-Bi-Ag-Au)

alabandite MnS 25 light grey 140-270 isotropic lamellar twinning; brown or
green internal reflections
(sulphides, Mn-carbonates)
anatase TiO, 20 light grey 580-620 weak abundant colourful internal reflections; 164
low temp. polymorph resembles rutile
(Fe-Ti-0, pyrite)

argentite Ag,S 30 light grey 20-60 isotropic
high temp. polymorph (greenish) (Ag-sulphides, Cu-Pb-S, Au)

armalcolite (Fe,Mg)Ti,O, 13-14 grey ? moderate barrel shape
(brownish) (Fe-Ti-0, moon)
arsenopyrite Fe AsS 52 white 1050-1130 distinct rhomb shape, twinning, zoning 140
(Sulphides, oxides, Au-Bi-Te-Sn, W)
bismuth Bi 60-65 bright white 10-20 distinct tarnishes brown, multiple twinning
(Co-Ni-As-S, A u-Bi, Te)

bismuthinite Bi,S, 40-50 white (bluish) 70-220 very strong fibrous, straight extinction
(Co-Ni-As-S, Au-Bi-Te, Mo, Sn, W)