The new Fe2+-rich variety of szaibélyite and its crystal-chemical peculiarities

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Marco E. Ciriotti
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The new Fe2+-rich variety of szaibélyite and its crystal-chemical peculiarities

Messaggio da Marco E. Ciriotti » sab 10 apr, 2021 18:29

Referenza:
▪ Zubkova, N.V., Pekov, I.V., Chukanov, N.V., Chaikovskiy, I.I., Yapaskurt, V.O., Pushcharovsky, D.Yu. (2020): The new Fe2+-rich variety of szaibélyite and its crystal-chemical peculiarities. Zapiski RMO (Proceedings of the Russian Mineralogical Society), 149(2), 72-79.

Abstract:
A new, unusually Fe2+-enriched variety of szaibélyite has been found in the hydrothermal assemblage in the contact zone between kimberlite and a halite rock in the Internatsional’naya kimberlite pipe, Sakha (Yakutia) Republic, Russia. The mineral forms light-green crusts up to 1.5×1.5×0.05 cm inside fractures in ekaterinite aggregates. Its chemical composition (electron microprobe, H2O calculated by stoichiometry) is: MgO 25.52, FeO 28.45, B2O3 36.84, H2O 9.42, total 100.23 wt %; the empirical formula: (Mg1.21Fe2+0.76)Σ1.97B2.02O4(OH)2. The IR spectrum is given and discussed. The crystal structure of the Fe2+-rich szaibélyite variety is solved based on single-crystal XRD data; R = 5.73%. The mineral is monoclinic, P21/c, a = 3.1714(2), b = 10.4561(7), c = 12.6498(9) Å, β = 95.548(7)°, and V = 417.51(5) Å3. Mg and Fe2+ cations are partially ordered between two octahedral sites, the structural formula is: (Fe2+0.51Mg0.49)(Mg0.73Fe2+0.27)(OH)[B2O4(OH)] (Z = 4).
Marco E. Ciriotti

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