Original paper

Veselovskyite, triclinic (Zn,Cu,Co)Cu4(AsO4)2(AsO3OH)2 9H2O, a Zn-dominant analogue of lindackerite

Sejkora, Jiří; Ondruš, Petr; Novák, Milan

Abstract

Veselovskýite, (Zn,Cu,Co)Cu4(AsO4)2(AsO3OH)2 · 9H2O, is a new supergene mineral from the Geister vein, Mine Rovnost at the Jáchymov ore district (St. Joachimsthal), Czech Republic, commonly associated with strashimirite and blue amorphous Cu arsenate. It forms aggregates, up to 8 × 5 × 1 mm in size, consisting of lath-like to thin-tabular crystals, up to 1 mm long, commonly forming complicated intergrowths, no twinning was observed. Veselovskýite is translucent (aggregates) to transparent (crystals), colourless to greyish white (with a slight greenish tint). It has a greyish white streak with a greenish tint, a vitreous luster, does not fluoresce under both short- and long-wave ultraviolet light. Cleavage on {001} is perfect, Mohs hardness is ∼2-3, and veselovskýite is very brittle with an irregular fracture and calculated density 3.28 g/cm3. Veselovskýite is biaxial positive, the indices of refraction are nx´ 1.645(3), ny´ 1.68(1), nz´ ∼1.72, 2V(calc) approximative 88°, it is strongly pleochroic (nx = greenish, ny = pale green, nz = green), and the optical orientation is as follows: nx´ versus elongation (c) = 15(1)°. Veselovskýite is triclinic, space group P-1, a 6.4022(4), b 8.0118(4), c 10.3665(4) Å, α 85.491(3)°, β 79.377(4)°, γ 84.704(5)°, V 519.34(4) Å3, Z = 1, a:b:c = 0.7991:1:1.2939. The eight strongest lines in the X-ray powder diffraction pattern are as follows: d (Å), I, (hkl): 10.185, 100 (001), 7.974, 12 (010), 3.987, 13 (020), 3.637, 15 (0-21), 3.395, 37 (003), 3.238, 15 (022), 2.910, 12 (202), 2.668, 16 (023). The chemical analyses by electron microprobe yielded MgO 0.05, CaO 0.04, MnO 0.22, NiO 0.30, CoO 0.96, CuO 32.98, ZnO 3.39, Al2O3 0.24, P2O5,As2O5 43.16, H2O 17.90, total (100.00) wt.%. The resulting empirical formula on the basis of 25 (O, OH, H2O) anions is (Zn0.43Cu0.24Co0.13Al0.05Ni0.04Mn0.03Mg0.01Ca0.01)Σ0.94 Cu4.00 [(AsO4)1.92(PO4)0.11(AsO3OH)1.92] · 9.20H2O. The ideal end-member formula ZnCu4[(AsO4)2(AsO3OH)2] · 9H2O requires ZnO 7.83, CuO 30.61, As2O5 44.22, H2O 17.34, total 100.00 wt.%. Veselovskýite is isostructural with lindackerite and represents Zn-dominant analogue of lindackerite and pradetite. The name veselovskýite is in honor of František Veselovský (*1948), an outstanding Czech mineralogist, who described several new minerals from the Jáchymov ore district.

Keywords

veselovskÝitenew mineral speciesarsenatejÁchymovkruŠnÉ hory mountainsczech republic