Abstract
AbstractOmariniite, ideally Cu8Fe2ZnGe2S12, represents the Ge-analogue of stannoidite and was found in bornite-chalcocite-rich ores near the La Rosario vein of the Capillitas epithermal deposit, Catamarca Province, Argentina. The mineral is associated closely with three other Ge-bearing minerals (putzite, catamarcaite, rarely zincobriartite) and bornite, chalcocite, digenite, covellite, sphalerite, tennantite, luzonite, wittichenite, thalcusite and traces of mawsonite. The width of the seams rarely exceeds 60 μm, their length can attain several 100 μm. The mineral is opaque, orange-brown in polished section, has a metallic lustre and a brownish-black streak. It is brittle, and the fracture is irregular to subconchoidal. Neither cleavage nor parting are observable in the sections. In plane-polarized light omariniite is brownish-orange and has a weak pleochroism. Internal reflections are absent. The mineral is distinctly anisotropic with rotation tints varying between brownish-orange and greenish-brown. The average result of 45 electron-microprobe analyses is Cu 42.18(34), Fe 9.37(26), Zn 5.17(43), In 0.20(6), Ge 11.62(22), S 31.80(20), total 100.34(46) wt.%. The empirical formula, based on Σ(Me + S) = 25, is Cu8.04(Fe2.03In0.02)Σ2.05Zn0.96 Ge1.94S12.01, ideally Cu8+Fe2+Zn2+Ge24+S122-. Omariniite is orthorhombic, space group I222, with unit-cell parameters: a = 10.774(1), b = 5.3921(5), c = 16.085(2) Å, V = 934.5(2) Å3, a:b:c = 1.9981:1:2.9831, Z = 2. X-ray single-crystal studies (R1 = 0.023) revealed the structure to be a sphalerite derivative identical to that of stannoidite. Omariniite is named after Dr. Ricardo Héctor Omarini (1946–2015), Professor at the University of Salta, for his numerous contributions to the geology of Argentina.
Highlights
Omariniite is one of the six germanium-bearing sulfides occurring at Capillitas; among them, putzite, (Cu4.7Ag3.3)Σ8GeS6 (Paar et al, 2004), catamarcaite, Cu6GeWS8 (Putz et al, 2006), and omariniite, previously named “Ge-stannoidite” (Paar et al, 2004; Putz, 2005; Putz et al, 2006), have here their type-locality
The full characterization and description as new mineral species were later given by McDonald et al (2016) and Bindi et al (2016) who described zincobriartite and spryite, respectively
The reflectance values for omariniite are generally markedly lower than those observed for stannoidite
Summary
Omariniite is one of the six germanium-bearing sulfides occurring at Capillitas; among them, putzite, (Cu4.7Ag3.3)Σ8GeS6 (Paar et al, 2004), catamarcaite, Cu6GeWS8(Putz et al, 2006), and omariniite, previously named “Ge-stannoidite” (Paar et al, 2004; Putz, 2005; Putz et al, 2006), have here their type-locality. The empirical formula, based on Keywords: omariniite, new mineral species, copper-iron-zinc-germanium-sulfide, electronmicroprobe analyses, reflectance data, crystal structure, La Rosario vein, Capillitas district, Catamarca Province, Argentina. Both nekrasovite and vinciennite have been frequently observed in high-sulfidation stage ore from several veins of the Capillitas deposit
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