Emilite, Cu10.72Pb10.72Bi21.28S48, the last missing link of the bismuthinite-aikinite series?
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Dan Topa, Werner H. Paar, Tonci Balic Zunic
Emilite, ideally Cu10.72Pb10.72Bi21.28S48, with a 4.0285(8), b 44.986(9), c 11.599(2) Å, space group Pmc21, Z = 1, is a new Cu-Pb-Bi sulfosalt found in quartz veins of the Felbertal scheelite deposit, Salzburg Province, Austria. It occurs as rare elongate homogeneous crystals, up to 0.3 mm long and 0.1 mm in diameter. The associated minerals are: bismuthinite derivatives in the range krupkaite-hammarite, Ag-bearing lillianite, makovickyite, pavonite, cosalite, galenobismutite, cannizzarite, tetradymite, native bismuth, chalcopyrite, pyrite and quartz. Emilite is opaque, with a metallic luster and a greyish black streak. In refl ected light, it has a greyish white color with a distinct anisotropy and perceptible birefl ectance in air and oil, without internal refl ections. The measured values of refl ectance in air are: 39.4-46.95 (470 nm), 39.21-48.25 (546 nm), 38.98-48.35 (589 nm), 38.30-46.94 (650 nm). The Mohs hardness is 3½-4, according to a microhardness VHN50-100 of 242-287 kg/mm2. The average result of fi ve best point-analyses of emilite is: Cu 7.68(3), Pb 25.4(1), Bi 49.9(1), S 17.59(4) wt.%, total 100.6(1), from which an empirical formula Cu2.68Pb2.72Bi5.33S12.18 can be derived, on the basis of Bi + (Pb + Cu)/2 = 8 atoms. The ideal formula is Cu2.68 Pb2.68 Bi5.32 S12 and requires Cu 7.65, Pb 24.94, Bi 50.09, S 17.32, total 100%. The calculated density is Dcalc = 7.025 g/cm3. The strongest eight lines in the X-ray powder pattern [d in Å(I)(hkl)] are: 4.037(49)(082), 3.656(100)(043), 3.605(49)(141), 3.567(81)(0.12.1), 3.174(71)(142), 3.151(78)(181), 2.852(95)(182) and 2.577(49)(084). Emilite is a new superstructure of the bismuthinite-aikinite series with ordering periodicity equal to a four-fold structure with the bismuthinite substructure motif.
|Journal||The Canadian Mineralogist|
|Publication status||Published - 2006|
- The Faculty of Science - emilite, Austria, Felbertal scheelite deposit, sulfosalt, bismuthinite–aikinite series, new mineral species