The new platinum selenide luberoite Pt5Se4 from the Lubero region (Kivu Province, Zaire)
Jedwab, Jacques; Cervelle, Bernard; Gouet, Geneviève; Hubaut, Xavier; Piret, Paul
European Journal of Mineralogy Volume 4 Number 4 (1992), p. 683 - 692
published: Aug 11, 1992
manuscript accepted: Jan 22, 1992
manuscript received: Jul 2, 1991
ArtNo. ESP147050404001, Price: 29.00 €
Abstract The new platinum selenide luberoite, identical with the synthetic compound Pt5Se4, has been found in concentrates from placers worked for gold and platinum in the Lubero region (Kivu Province, Zaire). 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 21/c), 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 stoechiometric 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 461 kg mm-2. The minerals found associated with luberoite in the placers, as well as the minerals enclosed in the platinum grains, indicate that luberoite belongs to a platinum deposit, whose primary source-rocks are not yet definitively known, but are very likely of granodioritic affiliation.