New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. I. Yurmarinite, Na₇(Fe³⁺,Mg,Cu)₄(AsO₄)₆

Abstract

A new mineral, yurmarinite, Na 7 (Fe 3+ ,Mg,Cu) 4 (AsO 4 ) 6 , occurs in sublimates of the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with hatertite, bradaczekite, johillerite, hematite, tenorite, tilasite and aphthitalite. Yurmarinite occurs as well-shaped, equant crystals up to 0.3 mm in size, their clusters up to 0.5 mm and thin, interrupted crystal crusts up to 3 mm63 mm on volcanic scoria. Crystal forms are {101}, {011}, {100}, {110} and {001}. Yurmarinite is transparent, pale green or pale yellowish green to colourless. The lustre is vitreous and the mineral is brittle. The Mohs hardness is~4Ý. One direction of imperfect cleavage was observed, the fracture is uneven. D (calc.) is 4.00 g cm À3 . Yurmarinite is optically uniaxial (À), o = 1.748 (5), e = 1.720(3). The Raman spectrum is given. The chemical composition (wt.%, electron microprobe data) is Na 2 O 16.85, K 2 O 0.97, CaO 1.28, MgO 2.33, MnO 0.05, CuO 3.17, ZnO 0.97, Al 2 O 3 0.99, Fe 2 O 3 16.44, TiO 2 0.06, P 2 O 5 0.12, V 2 O 5 0.08, As 2 O 5 56.68, total 99.89. The empirical formula, calculated on the basis of 24 O atoms per formula unit, is (Na 6.55 Ca 0.28 K 0.22 ) S7.05 (Fe 3+ 2.48 Mg 0.70 Cu 0.48 Al 0.23 Zn 0.14 Ti 0.01 Mn 0.01 ) S4.05 (As 5.94 P 0.02 V 0.01 ) S5.97 O 24 . Yurmarinite is rhombohedral, R3 c, a = 13.7444 (2), c = 18.3077(3) Å , V = 2995.13(8) Å 3 , Z = 6. The strongest reflections in the X-ray powder pattern [d, Å (I)(hkl)] are: 7.. The crystal structure was solved from single-crystal X-ray diffraction data to R = 0.0230. The structure is based on a 3D heteropolyhedral framework formed by M 4 O 18 clusters (M = Fe 3+ > Mg,Cu) linked with AsO 4 tetrahedra. Sodium atoms occupy two octahedrally coordinated sites in the voids of the framework. In terms of structure, yurmarinite is unique among minerals but isotypic with several synthetic compounds with the general formula (Na 7Àx & x )(M 3+ 3+x M 2+ 1Àx )(T 5+ O 4 ) 2 in which T = As or P, M 3+ = Fe or Al, M 2+ = Fe and 0 4 x 4 1. The mineral is named in honour of the Russian mineralogist, petrologist and specialist in studies of ore deposits, Professor Yuriy B. Marin (b. 1939). The paper also contains a description of the Arsenathaya fumarole and an overview of arsenate minerals formed in volcanic exhalations.

Copper in Natural Oxide Spinels: The New Mineral Thermaerogenite CuAl2O4, Cuprospinel and Cu-Enriched Varieties of Other Spinel-Group Members from Fumaroles of the Tolbachik Volcano, Kamchatka, Russia

“…The Arsenatnaya fumarole was uncovered and first studied by us during fieldworks in July 2012. This active fumarole described in papers [18,19] is a near-meridional linear system of mineralized pockets (up to 10-15 cm wide) and cracks situated between blocks of basalt scoria and volcanic bombs in the near-surface part of the scoria cone. The length of the hot area belonging to Arsenatnaya is about 15 m and its width varies from 1-1.5 m in the southern end to 3-4 m in the northern part.…”

“…Valent states of cations were not determined by direct methods. For properly sublimate minerals (thermaerogenite, cuprospinel, gahnite, spinel, magnesioferrite and franklinite) Fe and Mn are considered as Fe 3+ and Mn 3+ , respectively, taking into account extremely oxidizing conditions of mineral deposition in Arsenatnaya and similar fumaroles [18]. This is clearly confirmed by the calculation of the empirical formulae using the scheme common for oxide spinels, on the basis of four O atoms per formula unit (apfu): Sums of divalent and trivalent cations are close to 2.00 and 3.00 apfu, respectively (Tables 2 and 3) that is typical for "2-3 spinels" with the general formula A 2+ B 3+ 2 O 4 [2,23].…”

Triple molybdates K3–x Na1+x M 4(MoO4)6 (M = Ni, Mg, Co) and K3+x Li1–x Mg4(MoO4)6 isotypic with II-Na3Fe2(AsO4)3 and yurmarinite: synthesis, potassium disorder, crystal chemistry and ionic conductivity

“…The lattice parameters are a = 13.28-13.79 and c = 18.36-18.59 Å for arsenates, a = 12.95-13.39 and c = 17.81-17.91 Å for phosphates, and a = 14.27-14.59 and c = 19.73-19.98 Å for molybdates. Some features of the crystal chemistry of this family have been discussed previously by different authors (d' Yvoire et al, 1988;Masquelier et al, 1995;Brunet, 2003;Savina et al, 2013b;Pekov et al, 2014).…”

“…3 )(AsO 4 ) 6 (Masquelier et al, 1995), Na 7 Fe 4 (PO 4 ) 6 (Lii, 1996) and a natural analogue of synthetic arsenates II-Na 3 Fe 2 (AsO 4 ) 3 and Na 7 Fe 4 (AsO 4 ) 6 , and yurmarinite, i.e. (Na, Ca, K) 7 (Fe 3+ , Mg, Cu) 4 (AsO 4 ) 6 (Pekov et al, 2014), the name of which could be used for this family of compounds and related structures. The lattice parameters are a = 13.28-13.79 and c = 18.36-18.59 Å for arsenates, a = 12.95-13.39 and c = 17.81-17.91 Å for phosphates, and a = 14.27-14.59 and c = 19.73-19.98 Å for molybdates.…”

Polyoxometalate chemistry at volcanoes: discovery of a novel class of polyoxocuprate nanoclusters in fumarolic minerals

“…Two new mineral species, arsmirandite and lehmannite, have been found in the active Arsenatnaya fumarole 29,30 located at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption 1975-1976, Tolbachik volcano, Kamchatka Peninsula, Far-Eastern Region, Russia (55°41′N 160°14′E, 1200 m asl). The mineral assemblages encasing these halide-arsenates were formed in the temperature range between 500 and 700 °C 22,30 and were located inside the fumarole.…”