IMA 2015-063 = feodosiyite

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Marco E. Ciriotti
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IMA 2015-063 = feodosiyite

Messaggio da Marco E. Ciriotti » mer 18 ott, 2017 9:40

Prossima pubblicazione.

Referenza:
▪ Pekov, I.V., Zubkova, N.V., Yapaskurt, V.O., Belakovskiy, D.I., Lykova, I.S., Vigasina, M.F., Ksenofontov, D.A., Britvin, S.N., Sidorov, E.G., Khanin, D.A., Pushcharovsky, D.Yu. (2018): Feodosiyite, Cu11Mg2Cl18(OH)8·16H2O, a new mineral from the Tolbachik volcano, Kamchatka, Russia. Neues Jahrbuch für Mineralogie - Abhandlungen, 195, (in press).

Abstract:
A new mineral feodosiyite Cu11Mg2Cl18(OH)8·16H2O is found in the Glavnaya Tenoritovaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. Closely associated minerals are belloite, avdoninite, sylvite, carnallite, chlorothionite, and dioskouriite. Feodosiyite forms tabular or prismatic crystals up to 0.02 × 0.1 × 0.1mm3 combined in interrupted incrustations up to 0.1 × 0.5 × 1cm3 overgrowing basalt scoria. The mineral is transparent, bright green, with vitreous lustre. Feodosiyite is brittle. Its Mohs’ hardness is ca 3. One direction of imperfect cleavage was observed, the fracture is uneven. Dmeas = 2.57(1), Dcalc = 2.563 g cm–3. Feodosiyite is optically biaxial (–), α = 1.660(3), β = 1.690(5), γ = 1.718(5), 2Vmeas = 90(5)°. The Raman spectrum is reported. The chemical composition (wt.%, electron-microprobe data, H2O calculated by total difference) is: MgO 5.39 (4.84 – 5.91), Cu 46.98, Cl 35.42, H2Ocalc 20.21, –O = Cl – 8.00, total 100.00. The empirical formula calculated based on 42 atoms O+Cl pfu is: Cu10.58Mg2.40Cl17.90(OH)8.06 · 16.04H2O. Feodosiyite is monoclinic, P21/c, a = 12.9010(6), b = 16.4193(5), c = 11.9614(5) Å, β = 113.691(6)°, V = 2320.20(17) Å3 and Z = 2. The strongest reflections of the powder XRD pattern [d,Å(I)(hkl)] are: 11.87(100)(100), 6.585(15)(021), 5.969(25)(–102), 5.905(16)(200), 5.231(13)(121), 3.135(8) (222, – 412, –151) and 2.924(11)(– 333, – 251). The crystal structure, solved from single-crystal XRD data [R1(F) = 0.0867], is unique. It is based on layers of Cu2+-centred polyhedra. Cu2+ cations occupy six crystallographically non-equivalent sites that are placed in distorted octahedra Cu(1,3,5)(OH)2Cl4, Cu(2)(OH)3Cl3, and Cu(6)(OH)2(H2O)Cl3 and distorted tetragonal pyramids Cu(4)(OH)2Cl3. Isolated almost regular Mg(H2O)6 octahedra, linked with the layers of Cu-centred polyhedra by H-bonds, occur in the interlayer space, as well as separate H2O molecules. The mineral is named in honour of the outstanding Russian geologist Feodosiy Nikolaevich Chernyshev (1856 –1914).
Marco E. Ciriotti

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Roberto Bracco
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Re: IMA 2015-063 = feodosiyite

Messaggio da Roberto Bracco » mer 18 ott, 2017 13:37

Molto interessante come specie... ma alla faccia dei "nomi che non si devono somigliare"... praticamente omofona con la ferdowsiite!
Roberto Bracco - AMI Liguria

Perché seguire il calcio, quando accanto c'è lo scandio e poco più in là il vanadio?

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