Une wakefieldite-(Ce) non plombifère : nouvelles données sur l'espèce minérale correspondant à l'orthovanadate de cérium

A mineral, incorrectly called wolframite, from Tifemine (Morocco), was identified as nonplumboan wakefieldite-(Ce). This is the second occurrence of wakefieldite-(Ce) in the world and the first one which is Pb-free. The mineral occurs as black to brownish black bundles of veinlets, exhibiting a perfect cleavage, in massive white quartz. Electron microprobe anal. gave: (Ce0.52La0.18Nd0.15Y0.07Pr0.05Sm0.02)Σ0.99(V0.92As0.08)Σ1.00O4. Crystal structure refinement in space group I41/amd confirmed the hypothesis of a zircon-type structure with a 7.354(3) and c 6.488(4) Å. X-ray powder diffraction data are given. The measured and calcd. d. values are 4.76 and 4.80 g/cm3, resp. The mineral has hardness 250 kg/mm2, is stable at least up to 1050°, and is uniaxial pos. with nω 1.97(2) (translucent pale brown), nε 2.16 (almost opaque hazel brown)