The new mineral okruschite (IMA No. 2013–097), the arsenate analogue of roscherite, was discovered in a hydrothermal vein cross-cutting rhyolite exposed in the Fuchs quarry, near Sailauf, Spessart Mountains, Bavaria, Germany. Associated minerals are braunite, Mn-bearing calcite and arseniosiderite. Okruschite forms tabular aggregates up to 0.15 × 0.3 × 0.3 mm in size of curved and somewhat misaligned laths. It is white, semitransparent; lustre is vitreous. Dmeas = 3.33(2), Dcalc = 3.340 g/cm3. Okruschite is optically biaxial (−), α = 1.671(3), β = 1.682(2), γ = 1.687(3), 2Vmeas = 65(5)°. The infrared spectrum is given. The chemical composition is (electron microprobe, B and Li by ICP MS, H2O by gas chromatography of ignition products, wt. %): Li2O 0.04, BeO 7.70, MgO 1.68, CaO 8.28, MnO 16.27, FeO 4.89, Al2O3 0.22, As2O5 51.11, H2O 11.0, total 101.19. The empirical formula based on 34 O atoms is: Ca1.99(Mn3.09Fe0.92Mg0.56Al0.06Li0.04) ∑4.67Be4.15(AsO4)5.99(OH)3.64 · 6.40H2O. The simplified formula is Ca2Mn2+5Be4(AsO4)6(OH)4 · 6H2O. Okruschite is monoclinic, C2/c, a = 16.33(4), b = 12.03(3), c 6.93(1) Å, β 94.84(5)°, V = 1357(4) Å3, Z = 2. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 9.68 (39) (110), 4.95 (34) (310), 4.17 (34) (−311), 3.25 (100) (−202, 330), 3.11 (32) (−421), 2.841 (27) (240), 2.711 (26) (600), 1.726 (26) (461, −552, 004). Okruschite is named after Professor Martin Okrusch, from Germany. Type material is deposited in the collections of the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow.

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