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Tazieffite, ideally [Pb.sub.20][Cd.sub.2][(As,Bi).sub.22][S.sub.50][Cl.sub.10], is a new mineral from the high-temperature fumaroles of the Mutnovsky volcano, Kamchatka Peninsula, Russian Federation. It occurs as tiny, slender, needleshaped crystals, up to 400 [micro]m long and 10 [micro]m across, generally forming fibrous aggregates. Tazieffite is closely associated with greenockite, galena, mutnovskite, kudriavite, and Cd-rich cannizzarite. Other minerals spatially associated are pyrite, anhydrite, and cristobalite. Tazieffite is silvery-gray in color, occasionally with a magenta tint when it forms aggregates of extremely fine needles. It has a black streak and metallic luster. In plane-polarized incident light, tazieffite is weakly bireflectant and weakly pleochroic from dark gray to a blue-gray. Between crossed polars, the mineral is weakly anisotropic, without characteristic rotation tints. Reflectance percentages measured in air ([R.sub.min] and [R.sub.max]) for a single grain are 33.9, 34.1 (471.1 nm), 32.8, 33.0 (548.3 nm), 32.4, 32.6 (586.6 nm), and 30.9, 31.1 (652.3 nm), respectively. Electron microprobe analyses yield the following ranges of concentrations: Pb 41.88-44.14 (avg. 42.90), Cd 0.87-1.16 (avg. 1.03), Sn 0.31-0.69 (avg. 0.48), Bi 20.43-22.94 (avg. 21.90), As 8.64-10.73 (avg. 9.66), S 16.10-17.48 (avg. 16.58), Se 0.82-1.28 (avg. 1.04), C12.39-2.77 (avg. 2.63), Br 0.09-0.15 (avg. 0.12), 1 0.27-0.58 (avg. 0.42). The empirical chemical formula, calculated on the basis of 44 cations, is [Pb.sub.20.06][([Cd.sub.0.89] [Sn.sub.0..39]In002).sub.[sigma]1. 30][([As.sub.12.9] [Bi.sub.10,15]).sub.[sigma]22.64] [([S.sub.50.08][Se.sub.1.28]).sub.[sigma].sub.51.36][([Cl.sub.7.18] [I.sub.0.32][Br.sub.0.15]).sub.[sigma]7.65]. Tazieffite is closely related to the halogen-sulfosalt vurroite, [Pb.sub.20] [Sn.sub.2][Bi.sub.22][S.sub.54][Cl.sub.6], both from a chemical and structural point of view. It represents the (Cd,As)-dominant of vurroite, according to the coupled heterovalent substitution [Sn.sup.4+] + 2[S.sup.2] [right arrow] [Cd.sup.2+] + 2[Cl.sup.-]. The crystal structure of tazieffite was refined in the space group C2/c to R = 0.0370 for 4271 reflections with I > 2[sigma](I). Unit-cell parameters are a = 8.3520(17), b = 45.5920(92), c = 27.2610(55) [Angstrom], [beta] = 98.84(3), with V = 10257(4) [[Angstrom].sup.3], and Z = 4. The structure of tazieffite consists of lozenge-shaped composite rods made of coordination polyhedra of Pb around an octahedrally coordinated (Cd,Sn,Pb) position, interconnected into layers parallel to (010). These layers are separated by ribbons of As and Bi in distorted octahedral coordination. The ribbons form wavy, discontinuous double layers of the PbS archetype. Lone electron pairs of As and Bi are accommodated in the central portions of the PbS-like layers. The possibility that small amounts of N[H.sup.+.sub.4] are incorporated in the crystal structure of tazieffite is discussed. The name of this new mineral species (IMA 2008-012) honors Haroun Tazieff (Warszawa, May 11, 1914-Paris, February 6, 1998), famous Belgian/French volcanologist, who was a pioneer in the field study of volcanoes and devoted his life to the study of volcanic gases. Keywords: Tazieffite, chloro-sulfosalt, Mutnovsky volcano, fumaroles, vurroite isotype

Mutnovskite, ideally [Pb.sub.2]As[S.sub.3](I,Cl,Br), is a new mineral from the high-temperature fumaroles of the Mutnovsky volcano, Kamchatka Peninsula, Russian Federation. It occurs as microscopic ruby-colored short-prismatic crystals up to 100 [micro]m across, closely associated with halogen-sulfosalts of Pb, Bi, and As, Cd-Pb-Bi sulfosalts, pyrite, anhydrite, and cristobalite. Mutnovskite is transparent in thin fragments with a dark-red to blue color. The crystals are soft and fragile. Cleavage and fracture were not observed and the Mohs hardness is approximately 2. In reflected light mutnovskite is silvery lead-grey in color with an iridescent tarnish. Pleochroism and anisotropy are not visible because of the strong orange internal reflections, especially in immersion. Reflectance percentages measured in air in the range 400-700 nm were tabulated. Reflectance percentages ([RM.sub.min], and [R.sub.max]) for the four COM wavelengths are 34.2, 34.6 (470 nm), 33.2, 33.5 (546 nm), 32.5, 32.7 (589 nm), and 31.4, 31.7 (650 nm), respectively. A mean of four electron microprobe analyses gave Pb 62.0(3), As 11.0(4), Bi 0.6(1), S 14.4(2), Se 0.2(3), I 8.9(3), CI 2.44(9), Br 1.1(7), Cu 0.03(2), Fe 0.01(1), total 100.7 wt%, corresponding, on the basis of a total of 7 atoms, to [Pb.sub.1.99][([As.sub.0.98][Bi.sub.0.02])).sub.[summation]1.00] [([S.sub.2.98][Se.sub.0.02]).sub.[summation]3.00][([I.sub.0.47][Cl.sub.0.46] [Br.sub.0.09]).sub.[summation1.02]. The nine strongest powder-diffraction lines [d in [Armstrong] (I/[I.sub.0])(hkl)] are: 4.69 (32) (002): 4.37 (67) (210): 3.34 (73) (020); 3.19 (100) (212); 2.715 (61) (022); 2.648 (66) (410); 2.539 (31) (213); 2.455 (29) (402); 1.894 (30) (232). Mutnovskite is orthorhombic, space group Pnma, with a = 11.543(1), b = 6.6764(7), and c = 9.359(1) [Armstrong], V = 721.3(1) [Armstrong], Z = 4. The crystal structure was solved and refined to R = 4.14%. It consists of three independent cation positions: Pb 1 and Pb2 have tricapped trigonal prismatic coordinations with S and I atoms (completed with one As atom in the case of Pb2), while As has threefold coordination with S atoms, which form the base of a trigonal pyramid with As at the apex. Pairs of Pb1-Pb2 prisms are connected in columns which extend along c. As[S.sub.3] coordinations are isolated from each other. S atoms and half of the Pb atoms form wavy close-packed layers. Two kinds of channels parallel to b occur between the layers. The smaller channels host As atoms close to the channel walls, with their lone-electron pairs occupying the median part, while the bigger ones accommodate rows of alternating halogen and Pb atoms. The new mineral is named after the type locality, the Mutnovsky volcano, Kamchatka Peninsula, Russian Federation. Keywords: Mutnovskite, chemical composition, new mineral, X-ray data, crystal struture, Kamchatka Peninsula, Mutnovsky volcano

A new mineral krasheninnikovite, ideally KNa2CaMg(SO4)3F, is found in the sublimates of an active fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with tenorite, thenardite, hematite, euchlorine, blödite, vergasovaite, and fluorophlogopite. Krasheninnikovite forms long-prismatic to acicular crystals up to 3 mm long and up to 20 µm thick. The crystals are combined in sheaf-like, radiating or open-work matted aggregates forming nests up to several cm³ or crusts. Krasheninnikovite is transparent, colorless in individuals and white in aggregates. The luster is vitreous. The mineral is brittle; the thinnest needles are flexible and elastic. The Mohs hardness is 2½-3. Cleavage was not observed. Dmeas is 2.68(1), Dcalc is 2.67 g/cm³. Krasheninnikovite is optically uniaxial (-), ω = 1.500(2), ε = 1.492(2). The IR spectrum is unique. The chemical composition (wt%, electron microprobe data) is: Na2O 15.48, K2O 6.92, CaO 11.51, MgO 9.25, MnO 0.15, FeO 0.04, Al2O3 0.23, SO3 53.51, F 3.22, Cl 0.16, -O=(F,Cl)2 -1.39, total 99.08. The empirical formula, calculated on the basis of 13 (O+F+Cl) apfu, is: K0.67Na2.27Ca0.93Mn0.01Mg1.04Al0.02(SO4)3.04F0.76Cl0.02O0.06. Krasheninnikovite is hexagonal, space group P63/mcm, a = 16.6682(2), c = 6.9007(1) Å, V = 1660.36(4) Å3, Z = 6. The strongest reflections of the X-ray powder pattern [d, Å I(hkl)] are: 4.286 22(121); 3.613 24(040); 3.571 17(221); 3.467 42(131); 3.454 43(002); 3.153 100(140), 3.116 22(022), 2.660 39(222), 2.085 17(440). The crystal structure was solved on a single crystal and refined on a powder sample by the Rietveld method, Rwp = 0.0485. The krasheninnikovite structure is unique. It is based upon a heteropolyhedral pseudo-framework consisting of CaO6 octahedra, MgO5F octahedra, and SO4 tetrahedra; K and Na cations are located in cavities. Krasheninnikovite is named in honor of the Russian geographer, ethnographer, and naturalist S.P. Krasheninnikov (1711-1755), one of the first scientists who researched Kamchatka. The type specimen is deposited in the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow. [ABSTRACT FROM AUTHOR]

Tazieffite, ideally Pb20Cd2(As,Bi)22S50Cl10, is a new mineral from the high-temperature fumaroles of the Mutnovsky volcano, Kamchatka Peninsula, Russian Federation. It occurs as tiny, slender, needle-shaped crystals, up to 400 μm long and 10 μm across, generally forming fibrous aggregates. Tazieffite is closely associated with greenockite, galena, mutnovskite, kudriavite, and Cd-rich cannizzarite. Other minerals spatially associated are pyrite, anhydrite, and cristobalite. Tazieffite is silvery-gray in color, occasionally with a magenta tint when it forms aggregates of extremely fine needles. It has a black streak and metallic luster. In plane-polarized incident light, tazieffite is weakly bireflectant and weakly pleochroic from dark gray to a blue-gray. Between crossed polars, the mineral is weakly anisotropic, without characteristic rotation tints. Reflectance percentages measured in air (Rmin and Rmax) for a single grain are 33.9, 34.1 (471.1 nm), 32.8, 33.0 (548.3 nm), 32.4, 32.6 (586.6 nm), and 30.9, 31.1 (652.3 nm), respectively. Electron microprobe analyses yield the following ranges of concentrations: Pb 41.88-44.14 (avg. 42.90), Cd 0.87-1.16 (avg. 1.03), Sn 0.31-0.69 (avg. 0.48), Bi 20.43-22.94 (avg. 21.90), As 8.64-10.73 (avg. 9.66), S 16.10-17.48 (avg. 16.58), Se 0.82-1.28 (avg. 1.04), Cl 2.39-2.77 (avg. 2.63), Br 0.09-0.15 (avg. 0.12), I 0.27-0.58 (avg. 0.42). The empirical chemical formula, calculated on the basis of 44 cations, is Pb20.06(Cd0.89Sn0.39In0.02)Σ1.30(As12.49Bi10.15)Σ22.64 (S50.08Se1.28)Σ51.36(Cl7.18I0.32Br0.15)Σ7.65. Tazieffite is closely related to the halogen-sulfosalt vurroite, Pb20Sn2Bi22S54Cl6, both from a chemical and structural point of view. It represents the (Cd,As)-dominant of vurroite, according to the coupled heterovalent substitution Sn4+ + 2S2- → Cd2+ + 2Cl-. The crystal structure of tazieffite was refined in the space group C2/c to R = 0.0370 for 4271 reflections with I > 2σ(I). Unit-cell parameters are a = 8.3520(17), b = 45.5920(92), c = 27.2610(55) Å, β = 98.84(3)°, with V = 10257(4) Å3, and Z = 4. The structure of tazieffite consists of lozenge-shaped composite rods made of coordination polyhedra of Pb around an octahedrally coordinated (Cd,Sn,Pb) position, interconnected into layers parallel to (010). These layers are separated by ribbons of As and Bi in distorted octahedral coordination. The ribbons form wavy, discontinuous double layers of the PbS archetype. Lone electron pairs of As and Bi are accommodated in the central portions of the PbS-like layers. The possibility that small amounts of NH4+ are incorporated in the crystal structure of tazieffite is discussed. The name of this new mineral species (IMA 2008-012) honors Haroun Tazieff (Warszawa, May 11, 1914-Paris, February 6, 1998), famous Belgian/French volcanologist, who was a pioneer in the field study of volcanoes and devoted his life to the study of volcanic gases. [ABSTRACT FROM AUTHOR]

Mutnovskite, ideally Pb2AsS3(I,Cl,Br), is a new mineral from the high-temperature fumaroles of the Mutnovsky volcano, Kamchatka Peninsula, Russian Federation. It occurs as microscopic rubycolored short-prismatic crystals up to 100 µm across, closely associated with halogen-sulfosalts of Pb, Bi, and As, Cd-Pb-Bi sulfosalts, pyrite, anhydrite, and cristobalite. Mutnovskite is transparent in thin fragments with a dark-red to blue color. The crystals are soft and fragile. Cleavage and fracture were not observed and the Mohs hardness is approximately 2. In reflected light mutnovskite is silvery lead-grey in color with an iridescent tarnish. Pleochroism and anisotropy are not visible because of the strong orange internal reflections, especially in immersion. Reflectance percentages measured in air in the range 400-700 nm were tabulated. Reflectance percentages (Rmin and Rmax) for the four COM wavelengths are 34.2, 34.6 (470 nm), 33.2, 33.5 (546 nm), 32.5, 32.7 (589 nm), and 31.4, 31.7 (650 nm), respectively. A mean of four electron microprobe analyses gave Pb 62.0(3), As 11.0(4), Bi 0.6(1), S 14.4(2), Se 0.2(3), I 8.9(3), Cl 2.44(9), Br 1.1(7), Cu 0.03(2), Fe 0.01(1), total 100.7 wt%, corresponding, on the basis of a total of 7 atoms, to Pb1.99(As0.98Bi0.02)Σ1.00(S2.98Se0.02)Σ3.00(I0.47Cl0.46Br0.09)Σ1.02. The nine strongest powder-diffraction lines [d in Å (I/I0) (hkl)] are: 4.69 (32) (002); 4.37 (67) (210); 3.34 (73) (020); 3.19 (100) (212); 2.715 (61) (022); 2.648 (66) (410); 2.539 (31) (213); 2.455 (29) (402); 1.894 (30) (232). Mutnovskite is orthorhombic, space group Pnma, with a = 11.543(1), b = 6.6764(7), and c = 9.359(1) Å, V = 721.3(1) ų, Z = 4. The crystal structure was solved and refined to R = 4.14%. It consists of three independent cation positions: Pb1 and Pb2 have tricapped trigonal prismatic coordinations with S and I atoms (completed with one As atom in the case of Pb2), while As has threefold coordination with S atoms, which form the base of a trigonal pyramid with As at the apex. Pairs of Pb1-Pb2 prisms are connected in columns which extend along c. AsS3 coordinations are isolated from each other. S atoms and half of the Pb atoms form wavy close-packed layers. Two kinds of channels parallel to b occur between the layers. The smaller channels host As atoms close to the channel walls, with their lone-electron pairs occupying the median part, while the bigger ones accommodate rows of alternating halogen and Pb atoms. The new mineral is named after the type locality, the Mutnovsky volcano, Kamchatka Peninsula, Russian Federation [ABSTRACT FROM AUTHOR]