TETRAROOSEVELTITE, BETA-BI(ASO4), A NEW MINERAL SPECIES FROM MOLDAVA DEPOSIT, THE KRUSNE-HORY MTS, NORTHWESTERN BOHEMIA, CZECH-REPUBLIC

Tetrarooseveltite, beta-Bi(AsO4), is tetragonal, space group I 4(1)/a, with a 5.085(5) angstrom, c 11.69(1) angstrom, V 303.3 angstrom3, Z = 4 and D(calc.) = 7.64 g/cm3. The strongest lines in the X-ray powder diffraction pattern are (d in angstrom, I, hkl) 4.66(11)(101), 3.066(1 00)(112), 2.546(12)(200), 1.797(11)(220), 1.581(10)(107), 1.551(17)(31 2). Tetrarooseveltite is isostructural with scheelite and dimorphous w ith rooseveltite. Tetrarooseveltite forms fine grained powder aggregat es with hardness about 2.5, it has an earthy luster, white to yellowis h-white colour and is non fluorescent. The mineral is uniaxial positiv e with mean index of refraction N(m) = 2.20(5) for Na light. Microprob e analyses yield an average composition of Bi2O3 66.96, As2O5 33.02, P 2O5 0.03, total 100.01 wt.% leading to a formula BiASO4. The mineral h as been found as an oxidation product Bi-Ag-As-Co-Ni containing fluori te - barite - quartz vein Josef at Moldava deposit, the Krusne Hory Mt s., Northwestern Bohemia, Czech Republic.