Page 239 - A Practical Introduction to Optical Mineralogy

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

jamesonite Pb.FeSb,S, 36-41 light grey 70-130 strong acicular with cleavage and twin
(greenish) lamellae parallel to length
(Fe-Pb-Sb-Ag-S)

kama cite (Fe,Ni) 60 white isotropic (Fe-Ni-S, Fe-Ti-Cr-0,
(bluish) meteorites)

lepidocrocite FeO(OH) 10-19 grey 690-780 very strong red to brown internal reflectioQs 170
(In limonite, Fe-minerals, gossans)
limonite FeO.OH.nH,O 16-19 bluish grey 690-820 strong abundant brown to red internal 170
(see goethite and (colourful) reflections
lepidocrocite) (replaces iron minerals)

linnaeite Co 3S. 45-50 white 350-570 isotropic cleavage II (100)
(pinkish) (Cu-Fe-Ni-S)
livingstonite HgSb.S, 35-40 light grey 70-130 strong scarce red internal reflections; more
(colourful) opaque than cinnabar
(Hg-Sb-S)

loellingite FeAs, 55 white 370-1050 very strong common twinning
(yellowish) (colourful) (Fe-Ni-As-S, Cu-Fe-S, U, Sn)
mackinawite (Fe,Ni,Co,Cu)S 22-45 light grey 50-60 very strong lamellae in Cu-Fe-S or Fe-N i-S
(pink red) phases
(Cu-Fe-Ni-S)

maghemite y-Fe,OJ 26 light grey 360-990 isotropic magnetic
(bluish) (Fe-Ti-0)

magnetite FeJO. 21 light grey 530-600 isotropic magnetic; octahedra, rounded; lamellar 163
(often inclusions of hematite or ilmenite
pinkish) (Fe-Ti-0)

manganite MnOOH 15-21 grey 370-800 strong elongate crystal aggregates;
(brownish) cleavages; twin lamellae; red internal
reflections; alters to pyrolusite
(Fe-Mn-0-Si, veins)

marcasite FeS, 49-55 white 940-1290 strong radiating aggregates of twins; 147
orthorhombic (slightly (colourful) intergrown with pyrite
yellowish) (sulphides in sedimentary rocks, veins)

melnicovite- - FeS, so white isotropi.c very fine grained aggregate; minute 150
pyrite (brownish) or weak pits; banding
anisotropy (sulphide in sedimentary rocks)

miargyrite AgSbS, 30-50 light grey 90-120 strong twinning; scarce red internal
(bluish) reflections; as inclusions in galena
(Ag-Pb-Sb-S)

millerite NiS 52-56 yellow 190-380 strong aggregates of acicular grains;
common twinning
(Cu-Fe-Ni-S)

molybdenite MoS, 15-37 grey to 20-30 very strong flakes, platelets, hexagonal ; poor 147
white polish
(Bi-Te-Au, Sn, W, sulphides)

niccolite NiAs 52-58 white 330-460 very strong cataclased grains in radiating 176
(orange botryoidal masses; twinning
or pinkish) (Ni-Co-Ag-As-U, sulphides)