PETITJEANITE, BI3O(OH)(PO4)2, A NEW MINERAL, AND ADDITIONAL DATA FOR THE CORRESPONDING ARSENATE AND VANADATE, PREISINGERITE AND SCHUMACHERITE

Petitjeanite occurs in association with bismutite, mixite, reichenbach ite, pyromorphite and malachite in silicified barite veins from Gadern heim (type locality) and Reichenbach near Bensheim, Odenwald, Hesse, G ermany and from mine dumps of the Pucher-Schacht, Schneeberg, Saxony, Germany. The mineral forms crusts and small spherically shaped aggrega tes of intergrown crystals. No cleavage was observed, fracture is conc hoidal and Mohs hardness is 4.5. The colour varies from white to dark brown, vanadium-bearing samples are yellow; the luster is vitreous to adamantine. Petitjeanite is biaxial positive, 2V 75(5)-degrees, disper sion r > v, n(alpha) = 2.06(2) and n(gamma) = 2.13(2). The most promin ent crystal forms are {010}, {100}, {001} and {011}; for preisingerite 18 different pinacoids were found. Petitjeanite and preisingerite for m twins by rotation on [010]. Petitjeanite is triclinic, space group P 1BAR, with a = 9.798 (3) angstrom, b = 7.250(3) angstrom, c = 6.866(2) angstrom, alpha = 88.28(2)-degrees, beta = 115.27(2)-degrees, gamma = 110.70(3)-degrees, V = 408.3(2) angstrom3, Z = 2, D(x) = 6.99 g/cm3. The 6 strongest lines of the powder diffraction pattern are [d(hkl) in angstrom (I)(hkl)]: 4.437 (46)(110), 3.247 (87)(202BAR), 3.188 (100)( 221BAR), 3.135 (95)(021BAR, 111), 3.026 (75)(112BAR, 211BAR, 210) and 2.953 (47)(310BAR). Microprobe analysis gave Bi2O3 76.04%, PbO 3.39%, P2O5 14.34 %, As2O5 2.99 %, H2O(calc) 1.18 %, sum 97.95 %. This yields the empirical formula 6Pb0.13)2.99O0.85(OH)1.15[(PO4)1.77(AsO4)0.23]2 .00 or idealized Bi3O(OH)(PO4)2. Petitjeanite is the phosphorus analog ue of preisingerite and schumacherite. X-ray and chemical data of seve ral different samples indicate, that preisingerite, schumacherite and petitjeanite form a complete solid solution series.