BARIUM-ZINC ALUMOPHARMACOSIDERITE AT CAP- GARONNE MINE (VAR, FRANCE)

Baryum-zinc alumopharmacosiderite ideally: (Ba.K)0.5 (Zn.Cu)0.5 (Al.Fe )4 (AsO4)3 (OH)5 . 5H2O occurs on a specimen found at Cap-Garonne mine (Var, France), with weilerite, mansfieldite, zeunerite, metazeunerite , comubite, pamauite and olivenite. The crystals, colorless, have a ps eudocubic habitus and are up to 0.3 mm. Streak colorless, lustre vitre ous, transparent. Mohs hardness 2.5. The mineral is non fluorescent, f racture irregular, brittle with two imperfect cleavages {100} and {001 }. A chemical analysis was carried out by means of electron probe: Al2 O3: 26.67; As2O5: 41.71; BaO: 6.88; K2O: 0.86; ZnO: 2.68; CuO: 0.76; F e2O3: 0.97 and H2O by difference 19.47. The crystal system is quadrati c, spatial group I42m, with a = 15.476(2), c = 15.675(4) angstrom, V = 3754(1 angstrom3 and z = 8. The density is 2.8 (meas) and 2.82 g/cm3 (calc). The strongest lines in the X-ray diffraction pattern are [d in angstrom, (hkl), I visual]: 7.834, (002), 100; 7.736, (200), 100; 3.9 16, (004), 40; 3.868, (400), 50; 3.165, (422), 50; 2.754, (404), 60. I t is biaxial (-) with 2V = 10-20-degrees; alpha = 1.560(2); beta, gamm a = 1.572(2).