IMA 2020-104 = stibiogoldfieldite

[Marco E. Ciriotti]

Referenza:
▪ Biagioni, C., Sejkora, J., Musetti, S., Makovicky, E., Pagano, R., Pasero, M., Dolníček, Z. (2022): Stibiogoldfieldite, Cu12(Sb2Te2)S13, a new tetrahedrite group mineral. Mineralogical Magazine, 86, (in press).

Abstract:
Stibiogoldfieldite, Cu12(Sb2Te2)S13, was approved as a new mineral species from the Mohawk mine, Goldfield mining district, Esmeralda County, Nevada, U.S.A. It occurs as metallic anhedral grains, dark grey in colour. It is associated with quartz, pyrite and an Ag-Bi-(S,Se) phase (holotype material) and with quartz, pyrite, calaverite, bismuthinite, bohdanowiczite, and the Ag-Bi-(S,Se) phase (cotype material). In reflected light, stibiogoldfieldite is isotropic, grey in color, with indistinct brownish shade. Reflectance data for the four COM wavelengths in air are [λ (nm): R (%)]: 470: 31.1; 546: 30.9; 589: 30.8; 650: 31.0. Electron microprobe analysis for holotype material gave (in wt% - average of 60 spot analyses): Cu 45.03(60), Ag 0.26(7), Fe 0.02(3), Zn 0.13(15), Sn 0.02(4), Pb 0.05(6), Sb 8.02(62), As 2.80(65), Bi 2.77(87), Te 15.15(1.24), S 24.50(32), Se 0.52(11), total 99.27(69). On the basis of (As + Sb + Te + Bi) = 4 atoms per formula unit (apfu), the empirical formula of stibiogoldfieldite is (Cu12.05Ag0.04Zn0.03Fe0.01)Σ12.13(Sb1.12As0.63Bi0.23Te2.02)Σ4.00(S12.99Se0.11)Σ13.10. Chemical data onan additional sample from the same locality (cotype material) gave the following results (in wt% - average of 181 spot analyses): Cu 43.84(63), Ag 0.21(7), Sb 5.92(78), As 2.63(45), Te 20.07(1.19), S 25.13(53), Se 0.97(35), total 99.47(66). On the basis of (As + Sb + Te + Bi) = 4 apfu, the empirical formula of cotype material is (Cu11.13Ag0.03)Σ11.16(Sb0.80As0.57Bi0.06Te2.57)Σ4.00(S12.84Se0.20)Σ13.04. Stibiogoldfieldite is cubic, I-43m, with unit-cell parameters a = 10.3466(17) Å, V = 1107.6(5) Å3, Z = 2 (holotype). Unitcell parameters for the cotype sample are a = 10.3035 (2) Å, V = 1093.83(7) Å3. The crystal structure of holotype stibiogoldfieldite was refined by single-crystal X-ray diffraction data to a final R1 = 0.032 on the basis of 285 reflections with Fo > 4σ(Fo) and 20 refined parameters. Stibiogoldfieldite is isotypic with other members of the tetrahedrite group.

[Marco E. Ciriotti]

Pubblicazione effettuata.

Referenza:
▪ Biagioni, C., Sejkora, J., Musetti, S., Makovicky, E., Pagano, R., Pasero, M., Dolníček, Z. (2022): Stibiogoldfieldite, Cu12(Sb2Te2)S13, a new tetrahedrite group mineral. Mineralogical Magazine, 86, 168-175.