IMA 2018-016 = majzlanite

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Marco E. Ciriotti
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IMA 2018-016 = majzlanite

Messaggio da Marco E. Ciriotti » mar 22 ott, 2019 17:59

Prossima pubblicazione.

▪ Siidra, O.I., Nazarchuk, E.V., Zaitsev, A.N., Shilovskikh, V.V. (2019): Majzlanite, K2Na(ZnNa)Ca(SO4)4, a new anhydrous sulphate mineral with complex cation substitutions from Tolbachik volcano. Mineralogical Magazine, 83, (in press).

A new mineral majzlanite, ideally K2Na(ZnNa)Ca(SO4)4, was found in high-temperature exhalative mineral assemblages in the Yadovitaya fumarole, Second scoria cone of the Great Tolbachik Fissure Eruption (1975-1976), Tolbachik volcano, Kamchatka Peninsula, Russia. Majzlanite closely associates with langbeinite and K-bearing thénardite. Majzlanite is grey with a bluish tint, has a white streak and vitreous luster. The mineral is soluble in warm water. Majzlanite is monoclinic, C2/c, a = 16.007(2), b = 9.5239(11), c = 9.1182(10) Å, β = 94.828(7)°, V = 1385.2(3) Å3, R1 = 0.03. The eight strongest lines of the X-ray powder diffraction pattern are (I-d-hkl): 40-3.3721-312, 56-3.1473-402, 65-3.1062-222, 50-2.9495-131, 100-2.8736-113, 70-2.8350-421, 45-2.8031-511, 41-2.6162-512. The following structural formula was obtained: K2Na(Zn0.88Na0.60Cu0.36Mg0.16)(Ca0.76Na0.24)(S0.98Al0.015Si0.005O4)4. The chemical composition determined by electron-microprobe analysis is (wt. %): Na2O 9.73, K2O 15.27, ZnO 11.20, CaO 7.03, CuO 4.26, MgO 1.07, Al2O3 0.47, SO3 51.34, SiO2 0.12, total 100.49. The empirical formula calculated on the basis of 16 O apfu is K1.99Na1.93Zn0.84Ca0.77Cu0.33Mg0.16(S3.94Al0.06Si0.01)O16 and the simplified formula is K2Na(Zn,Na,Cu,Mg)2(Ca,Na)(SO4)4. No natural or synthetic compounds directly chemically and/or structurally related to majzlanite are known to date. The topology of the heteropolyhedral framework in majzlanite is complex. An interesting feature of the structure of majzlanite is an edge-sharing of ZnO6 octahedra with SO4 tetrahedra.
Marco E. Ciriotti

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