Tsumoite, BiTe, is trigonal, P3m1, a = 4.422(2)A, c = 24.05(2)A, Z = 3[Bi2Te2], and is a new mineral with a sheet structure composed of 12 monoatomic layers in a cubic close–packed stacking sequence analogous to synthetic BiSe. It is silver–white in color, luster metallic and streak steel–grey, and has perfect basal cleavage. Specific gravity is 8.16 ± 0.05(meas), 8.23(calc). Vickers hardness is in the range 51–90 kg/mm2(15 g load). Under the ore microscope it is white with creamy tint, very weakly pleochroic, and moderately anisotropic. The reflectivity is higher than that of associate tetradymite. It occurs as tabular crystals associated with tetradymite, bismuthinite, cosalite, and galena in a clinopyroxene–garnet–quartz skarn from the Tsumo mine, Shimane Prefecture, Japan. The principal X–ray powder diffraction lines are: 4.78(w), 3.23(vs), 2.36(s), 2.21(s), 1.825(s), and 1.408(s); these being essentially identical with those of synthetic BiTe and distinct from, but very similar to, those of 15-layered hexagonal bismuth chalcogenide.

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