Pošepnýite, a new Hg-rich member of the tetrahedrite group from Příbram, Czech Republic

[摘要] The new mineral pošepnýite was found in the mine dump of the shaft No. 16 Háje, one of the mines in the Příbramuranium and base-metal district, central Bohemia, Czech Republic. Pošepnýite is associated with příbramite, dzharkenite, ferroselite, hakite-(Hg), tetrahedrite-(Zn), antimonselite and uraninite in a calcite-dominant gangue. The newmineral occurs as idiomorphic to hypidiomorphic grains up to 100 μm in size. Pošepnýite is steel-grey and has a metalliclustre. Mohs hardness is ca. 3.5–4; the calculated density is 6.23 g cm–3. In reflected light, pošepnýite is light brown.No bireflectance, pleochroism, anisotropy or internal reflections were observed. The average empirical formula, basedon electron-microprobe analyses (62 spot analyses), is (Cu3.33Ag0.28)Σ3.61(Hg3.43Cu2.50Zn0.03Cd0.03Fe0.01)Σ6.00(Sb3.88As0.12)Σ4.00(Se10.83S1.29)Σ12.12. The ideal formula is (Cu+3+x□3–x)Σ6(Hg2+4–xCu+2+x)Σ6Sb4(Se12.5□0.5)Σ13, 0 ≤ x << 2, which requires Cu12.25, Hg 30.93, Sb 18.77 and Se 38.05, total 100.00 wt. % (for x = 0) or Cu 17.65, Hg 23.87, Sb 19.32, Se 39.16, total100.00 wt. % (for x = 1). Pošepnýite is cubic, I–43m, a = 10.964(1) Å, with V = 574.82(15) Å3 and Z = 2. The strongest reflections of the calculated powder X-ray diffraction pattern are [d, Å (I) (hkl)] are: 3.165(100) (222), 2.930(24)(321), 2.0017(16) (521), 1.9381(65) (440), 1.6528(31) (622)]. According to the single-crystal X-ray diffraction data(Robs = 0.051), pošepnýite is isostructural with minerals of the tetrahedrite group. The cubic structure of pošepnýite is atetrahedral framework with cavities and a part of tetrahedra replaced by SbSe3 coordination pyramids. It has one typeof pyramidal Sb position, one type of tetrahedrally coordinated cation position M1 occupied by (Hg, Cu), and one typeof partly vacant cation site M2 with triangular coordination. The main anion site Se1 participates in all of these cationcoordination polyhedra. Minority anion ‘Se2’ ties the six coordination triangles of Cu2 in the cavity of the tetrahedralframework into one cluster. Pošepnýite is named after the František Pošepný, a famous 19th-century geologist, oftenregarded as the father of the modern economic geology.

[学科分类] 自动化工程

[关键词] pošepnýite;new mineral;tetrahedrite group;crystal structure;uranium deposit;Příbram