The new platinum selenide luberoite Pt5Se4 from the Lubero region (Kivu Province, Zaire)

The new platinum selenide luberoite, identical with the synthetic compound Pt5Se4, has been found in concentrates from placers worked for gold and platinum. The mineral is present as loose crystals and fragments smaller than 0.5 mm, and as inclusions in platinum grains. It is composed of Pt=75.76 and Se=24.24 wt%. Its symmetry is monoclinic (space group P 21c), with a=6.584Å; b=4.602Å; c=11.10Å; a:b:c=1.430:1:2.412; β=101.6°; V=329.5Å3. The three strongest diffraction lines are 1.875 (100), 2.93 (80) and 1.812(60)Å. The calculated density is 13.02 g cm-3, and the stoichiometric formula is Pt5Se4 for Z=2. The mineral is opaque and the maximum and minimum reflectance values in air for the COM wavelengths (470, 546, 589, 650 mm) are, respectively: 48.6/42.6; 53.0/46.7; 55.0/48.6; 58.0/51.5. It has a mean microhardness (VHN15 ) of 461kg mm-2. Luberoite probably belongs to a platinum deposit, whose primary source-rocks are very likely of granodioritic affiliation. -from AuthorsSCOPUS: NotDefined.j