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NEW DATA ON VINCENTITE

Mahmud Tarkian^1,, Karl-Heinz Klaska¹ and Eugen F. Stumpfl²

¹ Institute of Mineralogy and Petrology, University of Hamburg, Grindelallee 48, D–20146 Hamburg, Germany
² Institute of Geological Sciences, University of Leoben, Peter-Tunner Strasse 5, A-8700 Leoben, Austria

E-mail address: mtark{at}mineralogie.uni-hamburg.de

Vincentite was described in 1974 as a new palladium-bearing mineral species in platinum–gold concentrates from the Riam Kanan River, southeastern Borneo. Because of its small grain-size, it was not possible at that time to obtain satisfactory X-ray data. The mineral has now been re-investigated. In reflected light, it is light brownish grey; pleochroism and anisotropy are weak. Maximum and minimum values of reflectance in air for standard wavelengths (470, 546, 589 and 650 nm) are: 38.8/43.1; 45.4/51.3; 48.0/54.2 and 50.8/55.9, respectively. New electron-microprobe analyses confirm the formula (Pd,Pt)₃(As,Sb,Te) attributed earlier. The X-ray powder-diffraction patterns obtained with a microdiffractometer were indexed on a monoclinic cell with a 11.226(3), b 6.318(2), c 8.047(2) Å, ß 100.95(4)°, V 560.4(2) ų; a:b:c = 1.776:1:1.273. For Z = 8, the calculated density is 10.86 g/cm³. The strongest five lines in the X-ray pattern [d in Å(I)(hkl)] are: 1.800(10)(02), 1.775(9)(04), 1.758(8)(23), 1.745(8)(331) and 1.838(6)(600).

Keywords: vincentite, Pd mineral, new data, spectral reflectance, X-ray-diffraction pattern, unit-cell parameters.