Jasrouxite, a new Pb–Ag–As–Sb member of the lillianite homologous series from Jas Roux, Hautes-Alpes, France

The thallium-rich sulfosalt deposit of Jas Roux, situated in the Pelvoux Massif (Hautes-Alpesdepartement, France), occurs in a Triassic sedimentary series. Jasrouxite belongs to the early lead-containing stages of the Tl-As-Sb period of mineralization. It occurs in a silicified gangue, along with smithite and late realgar. Jarouxite forms dark gray anhedral grains with metallic luster, up to several millimeters in size, as well as aggregates of grains which range to more than 10 mm in diameter. From their surface, grains of jasrouxite are embayed by a three-phase myrmekite aggregate composed of stibnite, boscardinite and smithite. The mineral is brittle, with irregular fracture; no cleavage or parting was observed. In reflected light, color is off-white. Bireflectance is weak, in off-white tones; anisotropy is distinct. Rare straight twin lamellae occur in otherwise untwinned crystals. The empirical formula, on the basis of 132 apfu derived from the crystal-structure determination, is Cu0.79Ag14.64Pb4.10Tl0.05As15.37Sb24.87S72.18. Calculated density is