Viteite, Pd5InAs, a new mineral from the Monchetundra layered intrusion, Kola Peninsula, Russia

Abstract

Viteite, Pd5InAs, is a new mineral discovered in the Monchetundra layered intrusion, Kola Peninsula, Russia. It forms euhedral grains about 0.5 to 10 μm in size intergrown with irarsite (IrAsS), hollingworthite (RhAsS), zvyagintsevite (Pd3Pb), Au-Ag alloys, and tulameenite (Pt2CuFe), that are replaced by Pt-Pd-Fe-Cu alloys and Pt-Pd-Fe-Cu oxygenated compounds, all of which are embedded in chalcocite, goethite, and covellite. Viteite is brittle and has a metallic luster. In plane-polarized light, viteite is bright pinkish-white. The mineral is weakly anisotropic with rotation tints blue to pinkish brown; it exhibits no internal reflections. Reflectance values of viteite in air (R1, R2 in %) are 55.7, 54.0 at 470 nm; 59.2, 58.4 at 546 nm; 60.0, 60.4 at 589 nm; and 60.0, 62.6 at 650 nm. Eight electron-microprobe analyses of viteite give an average composition of Pd 71.90, Pt 1.60, Fe 0.98, Cu 0.59, In 11.48, Hg 1.42, Pb 0.40, As 10.70, total 99.07 wt.%, corresponding to the empirical formula (Pd4.92Pt0.06)Σ4.98(In0.73Fe0.12Cu0.07Hg0.05Pb0.01)Σ0.98As1.04 based on 7 atoms; the average of 12 analyses of its synthetic analogue is: Pd 73.72, In 16.37, As 9.80, total 99.90 wt.%, corresponding to Pd5.02In1.03As0.95. The density, calculated on the basis of the empirical formula, is 10.78 g/cm3. The mineral is tetragonal, space group P4/mmm, with a 3.98600(3), c 6.98385(8) Å, V 110.961(2) Å3, and Z = 1. The crystal structure of synthetic Pd5InAs was solved and refined using powder X-ray-diffraction data from synthetic Pd5InAs. Viteite crystallizes with the Pd5TlAs structure type. The strongest lines in the X-ray powder diffraction pattern of synthetic Pd5InAs [d in Å (I) (hkl)] are: 2.3281(45)(003), 2.1932(100)(112), 1.9928(33)(020), 1.2515(17)(115), 1.1857(25)(132). The mineral is named for the Vite river, which flows near the Monchetundra intrusion.