La bukovite, Cu3+x.Tl2Fe Se4-x, une nouvelle espèce minérale

Abstract

Bukovite, Cu₃₊ₓ.Tl₂FeSe₄₋ₓ was found at the Bukov and Petrovice (Moravia) ore deposits and in the deposit of Predborice (Bohemia), Czechoslovakia. It is tetragonal, diffraction symbol 4/mmmI⁻⁻⁻, with a = 3.976 ; c = 13.70 Å ; c/a = 3.447 ; Z = 1 ; d[calc.] = 7.40. The strongest lines of the powder pattern are : 2.998 (10) ; 2.600 (9) ; 2.255 (7) ; 1-771 (8) Å. Microprobe analyses gave a formula of Cu₃₊ₓ.Tl₂FeSe₄₋ₓ, with x[max] = 0.28. Macroscopically it forms grains of gray brownish colour with metallic luster ; cleavage perfect (001). In polished section it is pale grey ; bireflectance weak, anisotropy medium. Microhardness (Vickers) : 61 kg/mm² (P = 10 g) ; 64 kg/mm² (P = 20 g). Reflectivity (%) : 26.0-29.5 (4 400 Å), 23.8-26.2 (6 400 Å). Named after the Bukov ore deposit.