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Nickelalumite, ideally NiAl4(SO4)(OH)12(H2O)3, is a newly approved mineral from the Batken region, Kyrgyzstan, where it occurs in the Kara-Tangi and Kara-Chagyr uranium deposits. It formed in a zone of hydrothermal alteration of U–V-bearing carbonaceous siliceous schists, in association with quartz, calcite, alumohydrocalcite, allophane, crandallite, kyrgyzstanite, ankinovichite and an unknown Al–OH-mineral. It occurs as aggregates of colourless to pistachio-green radiating bladed crystals from 0.05 to 0.50 mm long. It is vitreous to transparent in thin flakes, has a white streak, and shows no fluorescence under long-wave or short-wave ultraviolet light. Cleavage is perfect parallel to {001} and no parting was observed. Mohs hardness is 2, it is brittle and has a splintery fracture. The calculated mass density is 2.231 g cm–3. In transmitted plane-polarized white light, nickelalumite is non-pleochroic, biaxial, α = 1.542(2), γ = 1.533(2), β could not be measured due to the almost negligible thickness of the flakes. EPMA chemical analysis gave Al2O3 39.94, SiO2 0.17, SO3 15.20, V2O3 0.29, FeO 0.15, NiO 8.00, ZnO 6.21, (H2O)calc. 31.87, total 101.83 wt%, H2O was determined by crystal-structure analysis, and the empirical formula is as follows: (Ni0.55Zn0.39V0.02Fe0.01)Σ0.97(Al3.99Si0.01)Σ4.00 (SO4)(OH)12(H2O)3 based on 4 (Al + Si) cations. There is considerable variation in substitution of Zn, Cu, Fe and V3+ for Ni and V5+ for S6+. Nickelalumite is monoclinic, P21/n, a = 10.2567(5), b = 8.8815(4), c = 17.0989(8) Å, β = 95.548(1)°, V = 1550.3(2) Å3, Z = 4. The crystal structure of nickelalumite was refined to an R1 index of 5.66% and consists of interrupted [NiAl4(OH)12] sheets intercalated with layers of {(SO4)2(H2O)3}; nickelalumite is a member of the chalcoalumite group. [ABSTRACT FROM AUTHOR]

Akopovaite, ideally Li2Al4(OH)12(CO3)(H2O)3, is a new hydrotalcite-supergroup mineral from the Karasu–Karavshinskoye Sn deposit, Turkestan Range, Kyrgyzstan. It occurs as white or pale yellowish rosette-like aggregates that are composed of tiny curved plates up to 20–30 μm. Akopovaite is associated with gibbsite, quartz, albite, microcline, muscovite, montebrasite, siderite, schorl and birnessite-like Fe–Mn oxides. Akopovaite has a perfect cleavage along {001}, the mineral is transparent and very soft (VHN = 24 that corresponds to Mohs hardness of ca. 1). Dmeas = 2.12(2) g/cm3 and Dcalc = 2.106 g/cm3. The Raman spectra contain bands of carbonate groups and bands of O–H stretching vibrations. The chemical composition (wt.%, electron microprobe for Al and Fe; ICP-OES for Li; CHN method for CO2 and H2O) is Li2O 6.43, Al2O3 45.79, Fe2O3 0.27, CO2 10.09, H2O 36.1, total 98.68. The empirical formula based on (Li + Al + Fe) = 6 apfu is Li1.94(Al4.05Fe0.02)Σ4.07(OH)12(CO3)1.03(H2O)3.03. The crystal structure was refined by the Rietveld method with RB = 0.006 and Rwp = 0.014. Akopovaite is monoclinic, C2/m, a = 5.0953(6), b = 8.877(1), c = 7.806(1) Å, β = 102.572(6)°, V = 344.61(8) Å3 and Z = 1. The polytype should be denoted as 1M. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 7.66(100)(001), 4.397(27)(020), 3.821(45)(002,021), 2.4881(27)(200), 2.2273(16)(201) and 1.9027(18)(202). Akopovaite is the first naturally occurring hydrotalcite-supergroup carbonate species of Al and Li; its synthetic analogue is known. [ABSTRACT FROM AUTHOR]