Cotype material of stibiogoldfieldite from the Mohawk mine, Goldfield, Nevada, U.S.A., has been examined in order to collect single-crystal X-ray diffraction data of Te-rich stibiogoldfieldite and to characterize the associated Ag–Bi–(S,Se) phase. Tellurium-rich stibiogoldfieldite, with empirical formula (Cu11.30Ag0.03)Σ11.33(Sb0.80As0.57Bi0.06Te2.57)Σ4.00(S12.83Se0.20)Σ13.03, is cubic, space group I-43m, with unit-cell parameters a = 10.2947(3) Å, V = 1091.04(10) Å3. Its crystal structure has been refined to R1 = 0.0161 for 397 unique reflections with Fo > 4σ(Fo) and 25 refined parameters. The structure refinement confirmed the occurrence of vacancy at the M(2) site, in agreement with the substitution M(2)Cu+ + X(3)(Sb/As)3+ = M(2)□ + X(3)Te4+. The Ag–Bi–(S,Se) phase was identified as the 6P homologue of the pavonite series, namely dantopaite. Its empirical formula is Cu1.36Ag4.39Pb0.12Bi12.62Sb0.06(S14.01Se7.91Te0.08), showing an exceptionally high Se content. Unit-cell parameters of Se-bearing dantopaite are a = 13.518(2), b = 4.0898(6), c = 18.984(3) Å, β = 106.816(6)°, V = 1004.7(3) Å3, space group C2/m. The crystal structure was refined to R1 = 0.0504 for 1230 unique reflections with Fo > 4σ(Fo) and 82 refined parameters. The metal excess (~ 0.55 atoms per formula unit) of this pavonite homologue is mainly due to the accumulation of Ag and Cu in the thin slab of the crystal structure, whereas the high Se content is related to the partial replacement of S preferentially occurring in the thick PbS-like slab. Selenium- and Pb-richer domains of dantopaite, with empirical formula Cu0.89Ag4.50Pb0.49Bi12.53Sb0.07(S11.26Se10.74), were also identified, as grains up to 30 μm in size intimately intergrown with bohdanowiczite, indicating the possibility of a wide Se-to-S substitution in dantopaite.
Tellurium-rich stibiogoldfieldite and Se-bearing dantopaite from Goldfield, Nevada, U.S.A.: new crystal chemical data
Musetti S.;Biagioni C.
;
2023-01-01
Abstract
Cotype material of stibiogoldfieldite from the Mohawk mine, Goldfield, Nevada, U.S.A., has been examined in order to collect single-crystal X-ray diffraction data of Te-rich stibiogoldfieldite and to characterize the associated Ag–Bi–(S,Se) phase. Tellurium-rich stibiogoldfieldite, with empirical formula (Cu11.30Ag0.03)Σ11.33(Sb0.80As0.57Bi0.06Te2.57)Σ4.00(S12.83Se0.20)Σ13.03, is cubic, space group I-43m, with unit-cell parameters a = 10.2947(3) Å, V = 1091.04(10) Å3. Its crystal structure has been refined to R1 = 0.0161 for 397 unique reflections with Fo > 4σ(Fo) and 25 refined parameters. The structure refinement confirmed the occurrence of vacancy at the M(2) site, in agreement with the substitution M(2)Cu+ + X(3)(Sb/As)3+ = M(2)□ + X(3)Te4+. The Ag–Bi–(S,Se) phase was identified as the 6P homologue of the pavonite series, namely dantopaite. Its empirical formula is Cu1.36Ag4.39Pb0.12Bi12.62Sb0.06(S14.01Se7.91Te0.08), showing an exceptionally high Se content. Unit-cell parameters of Se-bearing dantopaite are a = 13.518(2), b = 4.0898(6), c = 18.984(3) Å, β = 106.816(6)°, V = 1004.7(3) Å3, space group C2/m. The crystal structure was refined to R1 = 0.0504 for 1230 unique reflections with Fo > 4σ(Fo) and 82 refined parameters. The metal excess (~ 0.55 atoms per formula unit) of this pavonite homologue is mainly due to the accumulation of Ag and Cu in the thin slab of the crystal structure, whereas the high Se content is related to the partial replacement of S preferentially occurring in the thick PbS-like slab. Selenium- and Pb-richer domains of dantopaite, with empirical formula Cu0.89Ag4.50Pb0.49Bi12.53Sb0.07(S11.26Se10.74), were also identified, as grains up to 30 μm in size intimately intergrown with bohdanowiczite, indicating the possibility of a wide Se-to-S substitution in dantopaite.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
