Belogubite, a new mineral of the chalcanthite group from the Gayskoe deposit, the South Urals, Russia

Kasatkin A. V., Britvin S. N., Chukanov N. V., Škoda R., Agakhanov A. A., Belakovskiy D. I.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2019. V. 148. N 3. P. 30-43

https://doi.org/10.30695/zrmo/2019.1483.02

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Language: Russian 

Abstract

Belogubite, ideally CuZn(SO₄)₂·10H₂O, has been found in the supergene zone uncovered by the open pit at the Gayskoe massive sulfide Zn-Cu deposit (Orenburgskaya region, the South Urals, Russia). It is associated with dietrichite and may contain relics of quartz. Belogubite forms aggregates of blue grains up to 1 mm in size. The mineral is transparent with vitreous luster and white streak. Its color varies from pale equant to light blue. Cleavage and parting were not observed. The new mineral is brittle and has Mohsʼ hardness ca. 2½. Its density measured by floatation in bromoform+ethanol is 2.27(2) g/cm^–3, its calculated density is 2.249 g/cm^–3. Belogubite is biaxial (–), α = 1.512(2), β = 1.525(2), γ = 1.531(2); 2V (meas.) = 70(10)°, 2V (calc.) = 67.9°. Dispersion is noticeable, r < v. The mineral is nonpleochroic. Chemical composition of the holotype sample is (wt %, electron microprobe data, H₂O determined by thermogravimetry): MgO 1.12, MnO 0.10, FeO 3.15, CuO 8.98, ZnO 18.02, SO₃ 32.49, H₂O 36.75, total 100.61. Its empirical formula calculated on the basis of 18 O apfu is: (Cu_0.55Zn_0.45)Σ_1.00(Zn_0.64Fe_0.22Mg_0.14Mn_0.01)Σ_1.01S_1.99O_7.98·10.02H₂O. The structure was solved by direct methods and refined on the basis of 1797 independent reflections to R = 0.016. Belogubite is triclinic, P1 ̅ . Unit cell parameters are: a = 6.2548(1), b = 10.6112(2), c = 6.0439(1) Å, α = 82.587(1), β = 109.625(1), γ = 104.848(1)°, V = 364.81(1) ų, Z = 1. The strongest reflections of the powder XRD pattern are [d_obs, Å (I) (hkl)]: 5.73 (35) (100), 5.576 (47) (–110), 4.873 (100) (–111), 3.907 (31) (021), 3.719 (45) (0 –21), 3.229 (27) (111), 2.915 (25) (–221), 2.684 (26) (130). Belogubite is a new, CuZn-ordered member of the chalcanthite group having M1 cationic site preferentially occupied by Cu whereas M2 site is dominated by Zn with subordinate substitution of Fe²⁺ and Mg. The mineral is named in honor of Elena Vitalievna Belogub (born 1963), major researcher of the Institute of Mineralogy of the Urals Branch of Russian Academy of Sciences, Miass, Chelyabinsk Oblast, Russia, a well-known expert in the mineralogy of volcanic-hosted massive sulfide copper deposits of South Urals.

Key words: belogubite, new mineral, chalcanthite group, Gayskoe deposit, the South Urals