Original paper
Hyršlite, Pb8As10Sb6S32, a new N = 3;3 member of the sartorite homologous series from the Uchucchacua polymetallic deposit, Peru
Keutsch, Frank N.; Topa, Dan; Makovicky, Emil
European Journal of Mineralogy Volume 30 Number 6 (2018), p. 1155 - 1162
23 references
published: Dec 20, 2018
published online: Sep 7, 2018
manuscript accepted: May 11, 2018
manuscript revision received: May 10, 2018
manuscript received: Jan 25, 2018
Abstract
Hyršlite, Pb8As10Sb6S32, is a new member of the sartorite homologous series of Pb–(As,Sb) sulfosalts. It occurs in the Uchucchacua polymetallic deposit, Oyon district, Catajambo, Lima Department, Peru. Compositionally it lies between guettardite and twinnite on the one hand, and hendekasartorite on the other hand. Hyršlite is grey, opaque with metallic lustre. It is brittle, without observable cleavage or parting. Mohs hardness is derived as 4, based on VHN25 range of microhardness (202–221, mean 215 kg mm−2). Density (calc.) = 5.26 g cm−3 using a simplified chemical formula. Reflectance percentages (R min and R max) for the four standard COM wavelengths are 32.6, 39.0 (470 nm), 32.1, 38.5 (546 nm), 31.5, 37.9 (589 nm), and 30.7, 36.7 (650 nm), respectively. The formula based on 32 S atoms per formula unit (apfu) is Pb7.90Sb5.98As10.00S32. The unit cell of hyršlite was refined from single-crystal data, with monoclinic symmetry, space group P21 a = 8.475(3) Å, b = 7.917(3) Å, c = 20.039(8) Å, β = 102.070(6)o, V = 1314.8(9) Å3. The crystal structure of hyršlite contains 12 independent cation and 16 distinct sulfur sites. There are four fully occupied Pb sites, two fully occupied As sites, one Sb site and five mixed (As,Sb) sites. In projection parallel to the 8.5 Å axis, the crystal structure is a typical member of the sartorite homologous series, a sartorite homologue N = 3;3, and homeotype of twinnite and guettardite. Opposing surfaces of the tightly bonded double-layer in the (As,Sb)-rich slabs of the structure have different cation configurations – one resembles coordinations observed in guettardite but the opposite one, with (As,Sb) cation pairs and single polyhedra, appears unique among sartorite homologues.
Keywords
hyršlite • new mineral • sartorite homologue • Pb–(As,Sb) sulfosalt • Uchucchacua deposit • crystal structure