Original paper
New nickel-uranium-arsenic mineral species from the oxidation zone of the Belorechenskoye deposit, Northern Caucasus, Russia: I. Rauchite, Ni(UO2)2(AsO4)2·10H2O, a member of the autunite group
Pekov, Igor V.; Levitskiy, Viktor V.; Krivovichev, Sergey V.; Zolotarev, Andrey A.; Bryzgalov, Igor A.; Zadov, Aleksandr E.; Chukanov, Nikita V.
European Journal of Mineralogy Volume 24 Number 5 (2012), p. 913 - 922
published: Sep 26, 2012
Abstract
Rauchite, ideally Ni(UO2)2(AsO4)2·10H2O (IMA no. 2010-037), a new arsenate mineral species of the autunite group, was found at the Belorechenskoye deposit, Adygea Republic, Northern Caucasus, Russia. It is a supergene mineral associated with dymkovite, annabergite and goethite in cavities of a dolomite vein with primary uraninite (pitchblende), nickeline and gersdorffite. Rauchite forms pseudo-tetragonal lamellar crystals (the main form is {001}) up to 0.5 mm across, typically split, like a fan or open book, and their clusters or crusts as large as 2 mm. Rauchite is transparent to translucent and light yellowish-green. The lustre is vitreous. The mineral is brittle, the Mohs' hardness is ca. 2. The cleavage is {001} perfect. Dcalc is 3.427 g cm3. Rauchite is optically biaxial (-), α = 1.550(3), β = 1.578(1), γ = 1.581(1), 2Vmeas = 40(5) , 2Vcalc = 36 . The average chemical composition (mean of eight electron-microprobe analyses) is (in wt%): MgO = 0.71, CoO = 0.07, NiO = 5.38, ZnO = 0.08, P2O5 = 1.08, As2O5 = 20.26, UO3 = 54.22, H2Ocalc = 17.10, and the total = 98.90. The empirical formula calculated on the basis of 22 O apfu is: (Ni0.76Mg0.19Co0.01Zn0.01)Σ0.97U2.00O4(As1.86P0.16)Σ2.02O810H2O. Rauchite is triclinic, space group I-1,a = 7.100(3), b = 7.125(3), c = 19.955(8) Å, α = 92.406(14), β = 94.924(14), γ = 90.420(6), V = 1004.7(7) Å3, Z = 2. [parameters of the reduced P cell are: a = 7.100(3), b = 7.125(3), c = 10.751(4) Å, α = 106.855(7), β = 104.366(7), γ = 90.420(6), V = 502.4(4) Å3, Z = 1]. The crystal structure was refined from single-crystal X-ray diffraction data obtained at 153 K (R
rauchite •
new mineral species •
arsenate •
autunite group •
uranium mica •
crystal structure •
oxidation zone •
belorechenskoye deposit •
adygea •
russia
Keywords