Reference:
▪ 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, 27-39.
Abstract:
A new mineral feodosiyite Cu11 Mg2 Cl18 (OH)8·16H2 O 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 pris- matic crystals up to 0.02 × 0.1 × 0.1 mm3 combined in interrupted incrustations up to 0.1 × 0.5 × 1 cm3 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. D meas = 2.57(1), D calc = 2.563 g cm–3. Feodosiyite is optically biaxial (–), α = 1.660(3), β = 1.690(5), γ = 1.718(5), 2 V meas = 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, H2 Ocalc 20.21, –O = Cl –8.00, total 100.00. The empirical formula calculated based on 42 atoms O+Cl pfu is: Cu10.58 Mg2.40 Cl17.90 (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)º, 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 Cu 2+ -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 H2 O molecules. The mineral is named in honour of the outstanding Russian geologist Feodosiy Nikolaevich Chernyshev (1856–1914).
▪ 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, 27-39.
Abstract:
A new mineral feodosiyite Cu11 Mg2 Cl18 (OH)8·16H2 O 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 pris- matic crystals up to 0.02 × 0.1 × 0.1 mm3 combined in interrupted incrustations up to 0.1 × 0.5 × 1 cm3 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. D meas = 2.57(1), D calc = 2.563 g cm–3. Feodosiyite is optically biaxial (–), α = 1.660(3), β = 1.690(5), γ = 1.718(5), 2 V meas = 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, H2 Ocalc 20.21, –O = Cl –8.00, total 100.00. The empirical formula calculated based on 42 atoms O+Cl pfu is: Cu10.58 Mg2.40 Cl17.90 (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)º, 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 Cu 2+ -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 H2 O molecules. The mineral is named in honour of the outstanding Russian geologist Feodosiy Nikolaevich Chernyshev (1856–1914).