M. F. Vigasina

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, Na7(Fe3+,Mg,Cu)4(AsO4)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 mm × 3 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 ~4½. One direction of imperfect cleavage was observed, the fracture is uneven. D(calc.) is 4.00 g cm-3. Yurmarinite is optically uniaxial (-), ω = 1.748(5), ε = 1.720(3). The Raman spectrum is given. The chemical composition (wt.%, electron microprobe data) is Na2O 16.85, K2O 0.97, CaO 1.28, MgO 2.33, MnO 0.05, CuO 3.17, ZnO 0.97, Al2 O3 0.99, Fe2O3 16.44, TiO2 0.06, P2O5 0.12, V2O5 0.08, As2O5 56.68, total 99.89. The empirical formula, calculated on the basis of 24 O atoms per formula unit, is (Na6.55Ca0.28K0.22)∑7.05(Fe3+2.48Mg0.70Cu0.48Al0.23Zn0.14 Ti0.01Mn0.01)∑4.05(As5.94P0.02V0.01)∑5.97O24. Yurmarinite is rhombohedral, R3̅ c, a = 13.7444(2), c = 18.3077(3) Å, V = 2995.13(8) Å3, Z = 6. The strongest reflections in the X-ray powder pattern [d,Å (I)(hkl)] are: 7.28(45)(012); 4.375(33)(211); 3.440(35)(220); 3.217(36)(131,214); 2.999(30)(223); 2.841(100)(125); 2.598(43)(410). 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 M4O18 clusters (M = Fe3+ > Mg,Cu) linked with AsO4 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 (Na7-x⃞x)(M3+3+xM2+1-x)(T5+O4)2 in which T = As or P, M3+ = Fe or Al, M2+ = Fe and 0 ≤ x ≤ 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.

Calorimetric determination of the enthalpy of formation for pyrophyllite

A calorimetric study of the natural pyrophyllite was performed by high-temperature melt calorimetry on a Tian-Calvet calorimeter. Based on experimentally determined in this work for pyrophyllite and gibbsite, as well as previously obtained for corundum and quartz, the total value of the enthalpy increment for the sample heated from room temperature to 973 K and the enthalpy of dissolution at 973 K by Hess’s law, the enthalpy of formation of pyrophyllite of Al2[(OH)2/Si4O10] composed of elements was calculated at 298.15 K: ΔfHelo(298.15 K) = −5639.8 ± 5.7 kJ/mol.

New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. IV. Shchurovskyite, K2CaCu6O2(AsO4)4 and dmisokolovite, K3Cu5AlO2(AsO4)4

Abstract Two new minerals shchurovskyite, ideally K2CaCu6O2(AsO4)4, and dmisokolovite, ideally K3Cu5AlO2(AsO4)4, are found in sublimates of the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka Peninsula, Russia. They are associated with one another and with johillerite, bradaczekite, tilasite, melanarsite, tenorite, hematite, aphthitalite, langbeinite, orthoclase, etc. Shchurovskyite occurs as coarse tabular or prismatic crystals up to 0.15 mm in size or anhedral grains forming parallel aggregates and crusts up to 1.5 cm × 2 cm across. Dmisokolovite forms tabular, prismatic or dipyramidal crystals up to 0.2 mm in size, commonly combined in clusters or crusts up to 0.7 cm × 1.5 cm across. Both minerals are transparent with a vitreous lustre. They are brittle, with Mohs’ hardness ≈ 3. Shchurovskyite is olive-green or olive drab. Dmisokolovite is bright emerald-green to light green. Dcalc = 4.28 (shchurovskyite) and 4.26 (dmisokolovite) g cm−3. Both are optically biaxial; shchurovskyite: (+), α = 1.795(5), β = 1.800(5), γ = 1.810(6), 2Vmeas = 70(15)°; dmisokolovite: (−), α = 1.758(7), β = 1.782(7), γ = 1.805(8), 2Vmeas = 85(5)°. The Raman spectra are given. Chemical data (wt.%, electron-microprobe; first value is for shchurovskyite, second for dmisokolovite):Na2O 0.00, 0.83;K2O 8.85, 10.71; Rb2O 0.11, 0.00;MgO 0.00, 0.35; CaO 4.94, 0.21; CuO 43.19, 38.67; ZnO 0.42, 0.20; Al2O3 0.04, 4.68; Fe2O3 0.00, 0.36; P2O5 0.59, 0.78; V2O5 0.01, 0.04; As2O5 40.72, 43.01; SO3 0.35, 0.00; total 99.22, 99.84. The empirical formulae, based on 18 O a.p.f.u., are shchurovskyite: K2.05Rb0.01Ca0.96Cu5.92Zn0.06Al0.01P0.09S0.05As3.86O18; dmisokolovite: Na0.28K2.36Mg0.09C a0.04Cu5.04Zn0.04 Al0.95Fe0.053+P0.11As3.88O18. The strongest reflections of X-ray powder patterns [d,Å(I)(hkl)] are shchurovskyite: 8.61(100)(200, 001), 5.400(32)(110), 2.974(32)(3̅12, 510), 2.842(47)(003, 020), 2.757(63) (6̅01, 511), 2.373(36)(512, 420) and 2.297(31)( 4̅21, 2̅22, 313); dmisokolovite: 8.34(95)(002), 5.433(84)(110), 2.921(66)(510, 3̅14), 2.853(58)(511, 020) and 2.733(100)(006, 512, 6̅02). Shchurovskyite is monoclinic, C2, a = 17.2856(9), b = 5.6705(4), c = 8.5734(6) Å, β = 92.953(6)°, V = 839.24(9) Å3 and Z = 2. Dmisokolovite is monoclinic, C2/c, a = 17.0848(12), b = 5.7188(4), c = 16.5332(12) Å, β = 91.716(6)°, V = 1614.7(2) Å3 and Z = 4. Their crystal structures [single-crystal X-ray diffraction data, R = 0.0746 (shchurovskyite) and 0.1345 (dmisokolovite: model)] are closely related in the topology of the main building units. They are based on a quasi-framework consisting of AsO4 tetrahedra and polyhedra centred by Cu in shchurovskyite or by Cu and Al in dmisokolovite. K and Ca are located in channels of the quasi-framework. The minerals are named in honour of outstanding Russian geologists and mineralogists Grigory Efimovich Shchurovsky (1803−1884) and Dmitry Ivanovich Sokolov (1788-1852).

New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. II. Ericlaxmanite and kozyrevskite, two natural modifications of Cu4O(AsO4)2

Abstract Two new minerals, ericlaxmanite and kozyrevskite, dimorphs of Cu4O(AsO4)2, were found 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. They are associated with each other and with urusovite, lammerite, lammerite-b, popovite, alarsite, tenorite, hematite, aphthitalite, langbeinite, As-bearing orthoclase, etc. Ericlaxmanite occurs as tabular, lamellar, equant or short prismatic crystals up to 0.1 mm in size, their clusters and pseudomorphs after urusovite crystal crusts up to 1.5 cm × 2 cm in area. Kozyrevskite occurs as prismatic crystals up to 0.3 mm long in clusters and as individual crystals. Both minerals are transparent with a vitreous lustre. They are brittle, with Mohs’ hardness ~3½. Ericlaxmanite is green to dark green. Kozyrevskite is bright grass green to light yellowish green; Dcalc is 5.036 (ericlaxmanite) and 4.934 (kozyrevskite) g cm-3. Both minerals are optically biaxial (–); ericlaxmanite: α = 1.870(10), β = 1.900(10), γ = 1.915(10), 2Vmeas = 60(15)°; kozyrevskite: α = 1.885(8), β = 1.895(8), γ = 1.900(8), 2Vmeas. = 75(10)°. The Raman spectra are given. Chemical data (wt.%, electron microprobe; the first value is for ericlaxmanite, the second for kozyrevskite): CuO 57.55, 58.06; ZnO 0.90, 1.04; Fe2O3 0.26, 0.12; SiO2 n.d., 0.12; P2O5 0.23, 1.23; V2O5 0.14, 0.37; As2O5 40.57, 38.78; SO3 0.17, 0.43; total 99.82, 100.15. The empirical formulae, based on 9 O a.p.f.u., are: ericlaxmanite: (Cu3.97Zn0.06Fe0.02)∑4.05(As1.94P0.02V0.01S0.01)∑1.98O9 and kozyrevskite: (Cu3.95Zn0.07Fe0.01)∑4.03(As1.83P0.09S0.03V0.02Si0.01)∑1.98O9. Ericlaxmanite is triclinic, P1̄ , a = 6.4271(4), b = 7.6585(4), c = 8.2249(3) Å , α = 98.396(4), β = 112.420(5), γ = 98.397(5)°, V = 361.11(3) Å3 and Z = 2. Kozyrevskite is orthorhombic, Pnma, a = 8.2581(4), b = 6.4026(4), c = 13.8047(12) Å , V = 729.90(9) Å3 and Z = 4. The strongest reflections in the X-ray powder patterns [d Å (I)(hkl)] are: ericlaxmanite: 3.868(46)(101), 3.685(100)(020), 3.063(71)(012), 2.957(58)(02̄ 2), 2.777(98)(2̄ 12, 2̄1 1), 2.698(46)(2̄1̄2) and 2.201(51)(013, 031); kozyrevskite: 3.455(100)(004), 3.194(72)(020, 104), 2.910(69)(022), 2.732(82)(122), 2.712(87)(301) and 2.509(92)(123). Their crystal structures, solved from single-crystal X-ray diffraction data [R = 0.0358 (ericlaxmanite) and 0.1049 (kozyrevskite)], are quite different. The ericlaxmanite structure is based on an interrupted framework built by edge- and corner-sharing Cu-centred, distorted tetragonal pyramids, trigonal bipyramids and octahedra. The kozyrevskite structure is based on complicated ribbons of Cu-centred distorted tetragonal pyramids and trigonal bipyramids. Ericlaxmanite is named in honour of the Russian mineralogist, geologist, geographer, biologist and chemist Eric Laxman (1737-1796). Kozyrevskite is named in honour of the Russian geographer, traveller and military man Ivan Petrovich Kozyrevskiy (1680-1734), one of the first researchers of Kamchatka.

Tourmaline in the Vetka Porphyry Copper-Molybdenum Deposit of the Chukchi Peninsula of Russia

Three generations of tourmaline have been identified in propylite in the Vetka porphyry copper-molybdenum deposit of the Chukchi Peninsula of Russia. Tourmaline-I is characterized by its Fetot/(Fetot + Mg) value, which ranges from 0.33 to 0.49. Tourmaline-II, which crystallizes at a lower temperature, overgrowing tourmaline-I or occurring as isolated crystals, is distinguished by a higher Fetot/(Fetot + Mg), which varies from 0.46 to 0.72. The Fetot/(Fetot + Mg) ratio in tourmaline-III, which overgrows tourmaline-II is lower (0.35–0.49), and is identical to that of the first tourmaline generation. This is probably caused by the beginning of sulfide deposition. Tourmalines in the deposit characterized by complex isomorphic substitutions can be attributed to the intermediate members of the dravite—“hydroxy-uvite”-“oxy-uvite” and schorl-“hydroxy-feruvite”-“oxy-feruvite” series. Tourmaline starts to crystallize at temperatures above 340°C. The fluid responsible for the tourmaline deposition was magmatic, with a significant admixture of meteoric water (δ18OH2O = −0.85 to −0.75‰). The high Fe3+/Fetot ratio (0.50) indicates high oxygen activity when the tourmaline precipitated. It has been established that the isomorphic substitution Fetot → Al is typomorphic of tourmalines from porphyry copper deposits worldwide.

Kyanoxalite, a new cancrinite-group mineral species with extraframework oxalate anion from the Lovozero alkaline pluton, Kola peninsula

Kyanoxalite, a new member of the cancrinite group, has been identified in hydrothermally altered hyperalkaline rocks and pegmatites of the Lovozero alkaline pluton, Kola Peninsula, Russia. It was found at Mount Karnasurt (holotype) in association with nepheline, aegirine, sodalite, nosean, albite, lomonosovite, murmanite, fluorapatite, loparite, and natrolite and at Mt. Alluaiv. Kyanoxalite is transparent, ranging in color from bright light blue, greenish light blue and grayish light blue to colorless. The new mineral is brittle, with a perfect cleavage parallel to (100). Mohs hardness is 5–5.5. The measured and calculated densitiesare 2.30(1) and 2.327 g/cm3, respectively. Kyanoxalite is uniaxial, negative, ω = 1.794(1), ɛ = 1.491(1). It is pleochroic from colorless along E to light blue along O. The IR spectrum indicates the presence of oxalate anions C2O42− and water molecules in the absence of CO32− Oxalate ions are confirmed by anion chromatography. The chemical composition (electron microprobe; water was determined by a modified Penfield method and carbon was determined by selective sorption from annealing products) is as follows, wt %: 19.70 Na2O, 1.92 K2O, 0.17 CaO, 27.41 Al2O3, 38.68 SiO2, 0.64 P2O5, 1.05 SO3, 3.23 C2O3, 8.42 H2O; the total is 101.18. The empirical formula (Z = 1) is (Na6.45K0.41Ca0.03)Σ6.89(Si6.53Al5.46O24)[(C2O4)0.455(SO4)0.13(PO4)0.09(OH)0.01]Σ0.68 · 4.74H2O. The idealized formula is Na7(Al5−6Si6−7O24)(C2O4)0.5−1 · 5H2O. Kyanoxalite is hexagonal, the space group is P63, a = 12.744(8), c = 5.213(6) -ray powder diffraction pattern are as follows, [d, [A] (I, %)(hkl)]: 6.39(44) (110), 4.73 (92) (101), 3.679 (72) (300), 3.264 (100) (211, 121), 2.760 (29) (400), 2.618 (36) (002), 2.216, (29) (302, 330). According to the X-ray single crystal study (R = 0.033), two independent C2O4 groups statistically occupy the sites on the axis 63. The new mineral is the first natural silicate with an additional organic anion and is the most hydrated member of the cancrinite group. Its name reflects the color (κɛανgoΣς is light blue in Greek) and the species-forming role of oxalate anions. The holotype is deposited at the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, registration no. 3735/1.

New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. III. Popovite, Cu5O2(AsO4)2

Abstract The new mineral popovite, Cu5O2(AsO4)2, was found in the 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 ericlaxmanite, kozyrevskite, urusovite, lammerite, lammerite-b, johillerite, bradaczekite, tenorite, hematite, aphthitalite, anhydrite, langbeinite, calciolangbeinite, As-bearing orthoclase, etc. Popovite occurs as prismatic or tabular crystals and as grains up to 0.2 mm in size forming clusters up to 1.5 mm in size and as crusts on basalt scoria or on aphthitalite incrustations. Popovite is transparent with a vitreous to greasy lustre. Its colour is olive green to dark olive-green, but fine-grained varieties are light yellow-green. The mineral is brittle, with Mohs’ hardness ~3 ½. Cleavage was not observed and the fracture is uneven. Dcalc is 5.30 g cm-3. Popovite is optically biaxial (+), α = 1.84(1), β ≈ 1.86, γ = 1.96(1), 2Vmeas = 50(20)°. The Raman spectrum is given. Chemical data (wt.%, electron-microprobe) are CuO 63.28, ZnO 0.56, V2O5 0.12, As2O5 35.80, SO3 0.27, total 100.03. The empirical formula, based on 10 O a.p.f.u., is (Cu4.99Zn0.04)S5.03(As1.95S0.02V0.01)S1.98O10. Popovite is triclinic, P1̄, a = 5.1450(3), b = 6.2557(3), c = 6.2766(4) Å, α = 100.064(5), β = 96.351(5), γ = 95.100(5)°, V = 196.47(1) Å3 and Z = 1. The strongest reflections in the powder X-ray diffraction pattern [d,Å (I)(hkl)] are 3.715(36)(110, 101), 3.465(43)(11̄1), 2.968(90)(01̄2), 2.927(100)(111), 2.782(31)(1̄02), 2.768(67)(1̄20), 2.513(55)(1̄2̄1) and 2.462(67)(2̄01). Popovite has a novel structure type. Its crystal structure, solved from single-crystal X-ray diffraction data (R = 0.0459), is based on (010) layers forming an interrupted framework. The layer consists of Cu(1)O6 octahedra with very strong Jahn-Teller distortion and Cu(2)O5 and Cu(3)O5 polyhedra. The linkage between the layers is reinforced by isolated AsO4 tetrahedra. Popovite is named in honour of the Russian mineralogists Vladimir Anatol’evich Popov (b. 1941) and Valentina Ivanovna Popova (b. 1941), a husband and wife research team working in the Institute of Mineralogy of the Urals Branch of the Russian Academy of Sciences, Miass, Russia.

Laachite, (Ca,Mn)2Zr2Nb2TiFeO14, a new zirconolite-related mineral from the Eifel volcanic region, Germany

The new mineral laachite was discovered in a sanidinite specimen from the Laach Lake (Laacher See) volcano, Eifel region, Rheinland-Pfalz, Germany. Associated minerals are sanidine, allanite-(Ce), baddeleyite, hauyne, hedenbergite, intermediate members of the jacobsite-magnetite series, phlogopite, rhodonite, spessartine, tephroite, thorite, zircon, and a pyrochlore-group mineral. Laachite is deep brownish-red, has an adamantine lustre, and is translucent; the streak is brownish red. It forms long-prismatic crystals up to 0.02 × 0.04 × 0.5 mm, which are present as random intergrowths and twins in cavities within sanidinite. The density calculated from the empirical formula is 5.417 g/cm 3 . The mean refractive index calculated from the Gladstone-Dale relationship is 2.26. The Raman spectrum shows the absence of hydrogen-bearing groups. The chemical composition is (electron microprobe, mean of 5 analyses, wt. %): CaO 4.29, MnO 9.42, FeO 5.73, Y 2 O 3 2.56, La 2 O 3 2.00, Ce 2 O 3 6.37, Nd 2 O 3 2.22, Al 2 O 3 0.99, ThO 2 7.75, TiO 2 10.98, ZrO 2 19.39, Nb 2 O 5 27.82, total 99.52. The empirical formula based on 14 O atoms is: (Ca 0.66 Mn 0.37 Th 0.25 Y 0.20 La 0.11 Ce 0.34 Nd 0.11 )(Zr 1.36 Mn 0.64 )(Nb 1.81 Ti 1.19 )(Fe 0.69 Al 0.17 Mn 0.14 )O 14.00 . The simplified formula, taking into account the structural data, is: (Ca,Mn) 2 (Zr,Mn) 2 Nb 2 TiFeO 14 . Laachite is monoclinic, space group C 2/ c , a = 7.3119(5), b = 14.1790(10), c = 10.1700(7) A, β = 90.072(2)°, V = 1054.38(1) A 3 , Z = 4. The crystal structure was solved using single-crystal X-ray diffraction data. Laachite is a monoclinic analogue of zirconolite-3 O , CaZrTi 2 O 7 , with Nb dominant over Ti in the octahedral sites Nb 1 and Nb 2 and Fe dominant in a site with four-fold coordination. The strongest lines of the powder X-ray diffraction pattern [ d , A ( I , %) ( hkl )] are: 4.298 (22) (022), 2.967 (100) (20–2, 202), 2.901 (59) (042), 2.551 (32) (15–1, 151, 240, 004), 1.800 (34) (24–4, 244), 1.541 (24) (37–1, 371), 1.535 (23) (20–6, 206), 1.529 (23) (046).

Thermochemical study of natural montmorillonite

The paper reports results of an experimental thermochemical study (in a heat-flux Tian-Calvet microcalorimeter) of montmorillonite from (I) the Taganskoe and (II) Askanskoe deposits and (III) from the caldera of Uzon volcano, Kamchatka. The enthalpy of formation ΔfHel0 (298.15 K) of dehydrated hydroxyl-bearing montmorillonite was determined by melt solution calorimetry: −5677.6 ± 7.6 kJ/mol for Na0.3Ca0.1(Mg0.4Al1.6)[Si3.9Al0.1O10](OH)2 (I), −5614.3 ± 7.0 kJ/mol for Na0.4K0.1(Ca0.1Mg0.3Al1.5Fe0.13+)[Si3.9Al0.1O10](OH)2 (II), −5719 ± 11 kJ/mol for K0.1Ca0.2Mg0.2(Mg0.6Al1.3Fe0.13+) [Si3.7Al0.3O10](OH)2 (III), and −6454 ± 11 kJ/mol for water-bearing montmorillonite (I) Na0.3Ca0.1(Mg0.4Al1.6)[Si3.9Al0.1O10](OH)2 · 2.6H2O. The paper reports estimated enthalpy of formation for the smectite end members of the theoretical composition of K-, Na-, Mg-, and Ca-montmorillonite and experimental data on the enthalpy of dehydration (14 ± 2 kJ per mole of H2O) and dehydroxylation (166 ± 10 kJ per mole of H2O) for Na-montmorillonite.

Cancrinite and cancrisilite in the Khibina-Lovozero alkaline complex: Thermochemical and thermal data

The paper presents the results of a thermochemical and thermal study of cancrinite, (Na6.93Ca0.545K0.01)Σ7.485[(Si6.47Al5.48Fe0.05)Σ12O24](CO3)1.25 · 2.30 H2O, and cancrisilite, (Na7.17 Ca0.01)Σ7.18[(Si7.26Al4.70Fe0.04)Σ12O24][(CO3)1.05(OH)0.21(PO4)0.04(SO4)0.01] · 2.635 H2O, from the Khibina-Lovozero Complex, Kola Peninsula, Russia. Stages of the thermal decomposition of these minerals were studied using IR spectroscopy. The enthalpies of formation of the minerals from elements were determined by melt drop solution calorimetry: ΔfHel0 (298.15 K) = −14 490 ± 16 kJ/mol for cancrinite and −14302 ± 17 kJ/mol for cancrisilite. The values of ΔfHel0 (298.15 K), So(298.15 K), and ΔfHel0 (298.15 K) are determined for cancrinite and cancrisilite of theoretical composition.