Stibioústalečite, Cu 6 Cu 6 (Sb 2 Te 2 )Se 13 , the first Te-Se member of tetrahedrite group, from the Ústaleč, Czech Republic

[摘要] Stibioústalečite, Cu12(Sb2Te2)Se13, was approved as a new mineral species from the Ústaleč mine, 15 km west ofHoražďovice, SW Bohemia, Czech Republic. It occurs as metallic anhedral grains up to 0.1–0.3 mm in size, dark grey incolor, in a calcite gangue. It is directly associated with hakite-(Hg), berzelianite, the not-yet approved phase Cu12(As2Te2)Se13 and uraninite. Stibioústalečite is brittle, with an indistinct cleavage and a conchoidal fracture; the calculated densityis 5.676 g/cm3. In reflected light, stibioústalečite is isotropic, and grey in color; internal reflections were not observed.Reflectance data for the four COM wavelengths in air are [λ (nm): R (%)]: 470: 33.3; 546: 33.2; 589: 33.1; 650: 33.0.Electron microprobe analysis for holotype material (grain used for single-crystal X-ray study) gave (in wt. % – average of 7 spot analyses): Cu 34.10, Ag 1.22, Fe 0.04, Zn 0.09, Hg 0.33, Sb 9.39, As 0.70, Te 12.41, S 3.76, Se 37.59,total 99.63. On the basis of (As+Sb+Te)=4 atoms per formula unit (apfu), the empirical formula of stibioústalečite is M(2)(Cu5.75Ag0.25)Σ6M(1)(Cu5.93Hg0.04Zn0.03Fe0.02)Σ6.02X(3)(Te2.12Sb1.68As0.20)Σ4(Se10.36S2.55)Σ12.91. The ideal formula is Cu6Cu6(Sb2Te2)Se13, which requires Cu 33.33, Sb 10.64 Te 11.16 Se 44.87, total 100 wt. %. Stibioústalečite is cubic, I4̄ 3m, with unit-cellparameters a = 10.828(4) Å, V = 1269.6(9) Å3, Z = 2. The crystal structure of stibioústalečite was studied by single--crystal X-ray diffraction data and it is isotypic with other members of the tetrahedrite group. The mineral is named afterits type locality Ústaleč and its chemical composition, being the (Sb/Te) end-member in the possible ústalečite series.

[学科分类] 自动化工程

[关键词] stibioústalečite;new mineral;tetrahedrite group;chemical composition;Ústaleč;Czech Republic