Unnamed Re-Mo-Cu sulfide from the Stillwater complex, and crystal chemistry of its synthetic equivalent spinel type (Cu, Fe) (Re, Mo)4S8
Tarkian, Mahmud; Housley, Robert M.; Volborth, Alexis; Greis, Ortwin; Moh, Günter H.
European Journal of Mineralogy Volume 3 Number 6 (1991), p. 977 - 982
published: Dec 19, 1991
manuscript accepted: May 29, 1991
manuscript received: Feb 15, 1991
ArtNo. ESP147050306006, Price: 29.00 €
Abstract A rhenium-rich sulfide was found as small inclusions in pentlandite and pyrrhotite hosted by pyroxenites of the Stillwater complex, Montana, USA. In reflected light, the mineral is isotropic and slightly darker than pyrrhotite. The reflectance values are (in air): 36.2% (470 nm), 36.2% (546 nm), 36.6 % (589 nm), and 37.5% (650 nm). The mineral has the chemical formula (Cu0.84Fe0.20Ni0.04)(Re2.72Mo1.16)S8.00, which can be simplified to (Cu,Fe)(Re, Mo)4S8. Because of the small size of the natural crystals, structural data were obtained from synthetic samples with analogous chemical composition and optical data. High-energy electron diffraction from single crystals and X-ray powder diffractometry gave the following results: face-centred cubic, space group F4̅3m (No. 216), a = 9.5408(1) Å, Z = 4 for the formula unit (Cu, Fe)(Re, Mo)4S8, V = 868.48(3) Å3, and ρcalc. = 7.34 gem-3. The structure of the title compound is closely related to a normal (2,3) spinel structure of the type [A2]t[B4]0S8 with the space group Fd3̅m. The symmetry reduction is mainly caused by vacancies on the tetrahedral A sites and some minor shifts of B and S atoms. Structural details of the mineral are discussed as well as its relationship to formerly reported rhenium sulfides.