Page 237 - A Practical Introduction to Optical Mineralogy

Mineral Formula - R % Colour - VHN Anisotropy Distinguished properties/resemblance See
range (associations) page

blaubleibender Cu ,+xS --> --> --> --> resembles covellite but R 0 blue in oil 144
covellite (Cu-Fe-S)

bornite Cu,FeS, 22 light pinkish 100 very weak tarnishes to blue or purple. 141
brown Intergrowths with chalcopyrite
(Cu-Fe-S)
boulangerite Pb,Sb,S 11 38-41 light grey 90-180 distinct stronger anisotropy than bournonite
(greenish) (Pb-Sb-S, Cu-Fe-S)
bournonite CuPbSbS, 35-37 light grey 130-210 weak common twinning
(bluish) (Pb-Sb-S, Cu-Fe-S)

braunite Mn,Si0 12 20-22 light grey 880-1190 weak resembles some manganese oxides;
(brownish) may be magnetic
(Mn-Fe-Si-0, mainly in
metamorphic rocks)
bravoite (Fe,Ni,Co)S, 31-->54 light grey to 670-1540 isotropic colour zoning 149
Ni,Co->Fe white (pyrite and other sulphides)
(brownish)
carrollite Co,CuS, 43 white 350-570 isotropic resembles linnaeite
(pinkish) (Co-Cu-Fe-S)

cassiterite SnO, 11-13 grey 1030-1080 distinct common twinning; strong colourless to 158
brown internal reflections; cleavage
(W, Bi, As, B, sulphides)

chalcocite Cu,S 32 light grey 70-100 weak lancet shaped twinning 142
(bluish) (colourful) (Cu-Fe-S)

chalcopyrite CuFeS, 42- 46 yellow 190-220 weak twinning; more yellow and softer than 143
pyrite; as inclusions in sphalerite
(Cu-Fe-Ni-S, sulphides)

chromite FeCr,O, 12 grey 1200-1210 isotropic rounded octahedra; resembles 160
(brownish) (weak magnetite but non-magnetic
anisotropy) (Fe-Ti-0)

cinnabar HgS 28-29 light grey 50-100 moderate multiple twinning; abundant red 144
(bluish) internal reflections; rare
(Hg-Sb-S, Fe-S)

cobaltite Co AsS 53 white 1180-1230 weak often idiomorphic cubic; colour 144
orthorhombic (pinkish) zonation; cleavage traces
(Cu-Fe-S, Co-Ni-As-S)

cohenite Fe,C white weak resembles iron
(Fe, Fe-0, Fe-Ni-S) meteorites

copper Cu 81 metallic pink 120-140 isotropic scratches easily 177
(tarnishes) (Cu-0, Cu-Fe-S)

covellite CuS 7-22 blue to 70-80 very strong plates and flakes; pleochroic 144
bluish light (fiery (Cu-Fe-S)
grey orange)

cryptomelane - K,Mn.o ,. 27 light grey 530-1050 distinct fibrous, botryoidal; resembles
psilomelane; straight extinction
(Fe-Mn-0)

cubanite CuFe,S, 40 light grey 150-260 strong lamellae within pyrrhotite,
chalcopyrite
orthorhombic (yellowish
brown) (Cu-Fe-S)