Thalhammerite, Pd
9Ag
2Bi
2S
4, is a new sulphide discovered in galena-pyrite-chalcopyrite and millerite-bornite-chalcopyrite vein-disseminated ores from the Komsomolsky mine of the Talnakh and Oktyabrsk deposits, Noril’sk region, Russia. It forms tiny inclusions (from a few μm up to about 40–50 μm) intergrown in galena, chalcopyrite, and also in bornite. Thalhammerite is brittle and has a metallic lustre. In plane-polarized light, thalhammerite is light yellow with weak bireflectance, weak pleochroism, in shades of slightly yellowish brown and weak anisotropy; it exhibits no internal reflections. Reflectance values of thalhammerite in air (R
1, R
2 in %) are: 41.9/43.0 at 470 nm, 43.9/45.1 at 546 nm, 44.9/46.1 at 589 nm, and 46.3/47.5 at 650 nm. Three spot analyses of thalhammerite give an average composition: Pd 52.61, Bi 22.21, Pb 3.92, Ag 14.37, S 7.69, and Se 0.10, total 100.90 wt %, corresponding to the empirical formula Pd
8.46Ag
2.28(Bi
1.82Pb
0.32)
Σ2.14(S
4.10Se
0.02)
Σ4.12 based on 17 atoms; the average of five analyses on synthetic thalhammerite is: Pd 55.10, Bi 24.99, Ag 12.75, and S 7.46, total 100.30 wt %, corresponding to Pd
8.91Ag
2.03Bi
2.06S
4.00. The density, calculated on the basis of the empirical formula, is 9.72 g/cm
3. The mineral is tetragonal, space group
I4/
mmm, with
a 8.0266(2),
c 9.1531(2) Å,
V 589.70(2) Å
3 and
Z = 2. The crystal structure was solved and refined from the single-crystal X-ray-diffraction data of synthetic Pd
9Ag
2Bi
2S
4. Thalhammerite has no exact structural analogues known in the mineral system; chemically, it is close to coldwellite (Pd
3Ag
2S) and kravtsovite (PdAg
2S). The strongest lines in the X-ray powder diffraction pattern of synthetic thalhammerite [
d in Å (
I) (
hkl)] are: 3.3428(24)(211), 2.8393(46)(220), 2.5685(21)(301), 2.4122(100)(222), 2.3245(61)(123), 2.2873(48)(004), 2.2201(29)(132), 2.0072(40)(400), 1.7481(23)(332), and 1.5085(30)(404). The mineral honours Associate Professor Oskar Thalhammer of the University of Leoben, Austria.
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