Abstract
AbstractChangchengite occurs in chromite orebodies in dunite and in platinum placer deposits in chromite orebodies nearby. The mineral occurs as massive aggregates or veinlets on margins of iridisite (IrS2) and replaces it. Opaque. Lustre metallic. Colour steel–black. Streak black. Hm = 3.7. VHN20= 165 kg/mm2. Isotropic. Cleavage none. Density 11.96 g/cm3. Seven electron microprobe analyses give the following mean chemical results (wt. %): S 7.2, Cu 0.3, Te 0.4, Ir 41.2, Pt 2.8 and Bi 47.3 with total 99.1. The simplified formula is IrBiS. The strongest X–ray powder diffraction lines (hkl, d, f) are 210, 2.75 (70); 211, 2.51 (60); 311, 1.860 (100); 440, 1.090 (50) and 600, 1.027 (50). The X–ray powder diffraction pattern is similar to that of mayingite. After the diffraction data are indexed the mineral is determined to be cubic. The space group is P 213 with a = 0.6164(4) nm, V = 0.2342 nm3 and Z = 4.
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