Urusovite, Cu[AlAsO5], a new mineral from the Tolbachik volcano, Kamchatka, Russia (original) (raw)

Original paper

Vergasova, Lidiya P.; Filatov, Stanislav K.; Gorskaya, Marina G.; Molchanov, Alexey A.; Krivovichev, Sergey V.; Ananiev, Vladimir V.

Abstract

Abstract Urosovite, ideally Cu[AlAs05], has been found in a fumarole in the North Breach of the great fissure Tolbachik eruption (1975-76, Kamchatka peninsula, Russia). It occurs as light-green plates up to 0.4 mm in maximal dimension, tabular on {100}, elongated along [001]: well-developed forms are {100}, {010}, {110}, {011}, {111}. Associated minerals are: ponomarevite. piypite. sylvite, dolerophanite, euchlorine, tenorite, hematite and two unknown As-bearing minerals. Urosovite is brittle and has a perfect cleavage on (100), a vitreous luster and a white streak. H = 378 kg/mm2. Biaxial, optically negative, a = 1.672(2), P = 1.718(2), y= 1.722(2), 2Vmeas - 30(2)°, 2Vcalc = 32.2°. Optical orientation is b = β c ~ α. Pleochroism is in the light-green tones: a - colourless. P - light-green, y - light-green. The mineral is monoclinic, space group P21/c, a = 7.314(2), b = 10.223(3), c = 5.576(2) A, p = 99.79(3)°. V = 410.9(2) Å3. Tlie diagnostic lines of the X-ray powder diffraction pattern are (I-d-hkl): 100-7.20-100: 9-4.844-011; 23-4.327-111; 10-3.604-200; 10-3.174-121; 20-3.125-211; 6-2.656-012; 8-2.458-221. Urosovite is isostroctural with Fe2+[AlP05]. Microprobe analysis gave the following chemical composition (wt. %): CuO 32.23 (30.97-32.82), Al2O3 20.89 (20.44-21.44), Fe2O3 0.32 (0.10-0.72), ZnO 0.25 (0.10-0.43), As2O5 46.02 (44.97-47.17), V2O5 0.12 (0.00-0.40), Σ99.83 (98.71-100.64). The empirical formula of urosovite. (Cu0.99Zn0.01)Σ1.00Al1.00As0.98O5.00, calculated on the basis of 5 O atoms, is close to the ideal one. CufAlAsO5], confirmed by crystal-strocture analysis. The mineral is named urosovite in honour of Vadim Sergeevich Urosov (1936-), crystal chemist. Corresponding Member of the Russian Academy of Sciences, chair of the Department of Ciystallography and Crystal Chemistry of Moscow State University.

Keywords

urusovite • new mineral • arsenate • Tolbachik volcano • Kamchatka (Russia).