Ziminaite, Fe3+VO4, a new howardevansite-group mineral from the Bezymyannyi volcano, Kamchatka, Russia

The new mineral ziminaite, ideally Fe 3+ VO 4 , was found in fumarole sublimates at the Bezymyannyi volcano, Kamchatka, Russia. Ziminaite occurs as lamellar, tabular or flattened prismatic crystals up to 10 × 30 × 50 μm typically epitaxially overgrowing koksharovite, and as aggregates (up to 0.15 mm) associated with bannermanite in cavities in volcanic scoria. The mineral is translucent, yellowish-brown with an adamantine luster. The calculated density is 3.45 g cm − 3 . In reflected light, ziminaite is light grey. Bireflectance is weak, internal reflections are deep yellow. The reflectance values [ R max –R min , % (λ, nm)] are: 17.7–16.3 (470), 15.7–14.1 (546), 15.1–13.8 (589), 14.7–13.6 (650). Chemical composition (wt%) is: MgO 2.20, CaO 0.01, Al 2 O 3 7.81, Fe 2 O 3 27.18, TiO 2 4.50, SiO 2 0.26, P 2 O 5 0.09, V 2 O 5 57.01, total 99.06. The empirical formula, based on 24 O atoms, is: (Fe 3 + 3.29 Al 1.48 Ti 0.54 Mg 0.53 ) Σ5.84 (V 6.05 Si 0.04 P 0.01 ) Σ6.10 O 24 (Z = 1). Ziminaite is triclinic, P 1 ¯ , a 8.012(4), b 9.345(5), c 6.678(3) Å, α 106.992(10), β 101.547(8), γ 96.594(11)º, V 460.4(4) Å 3 , Z = 6. The strongest reflections of the powder X-ray diffraction pattern [ d ,Å( I )( hkl )] are: 3.751(17)(1–21, 12 − 1), 3.539(86)(120), 3.270(67)(01–2), 3.209(100)(2–20), 3.090(20)(2–11, 002), 3.041(18)(03 − 1, 02–2), 2.934(14)(12 − 2, 030) and 1.665(24)(023, 12 − 4). The crystal structure, solved from single-crystal data ( R 1 = 0.085), is based upon heteropolyhedral framework built by VO 4 tetrahedra and Fe 3+ -centred octahedra and five-fold polyhedra. Ziminaite belongs to the howardevansite group being its first member without species-defining uni- or divalent cations and with all large cation sites vacant. The mineral is named after the Zimina volcano situated near the discovery locality.