Michael Zelenski

Sublimate speciation at Mutnovsky volcano, Kamchatka

Sublimates from high-temperature (470-507°C) gases at Mutnovsky volcano in southern Kamchatka were collected in silica glass tubes. Only particles of altered rocks were found in a transparent zone above 480°C. From 480 to 120°C, Fe and Cd sulphides with or without NaCl change to Cd-Pb-Bi and Pb-As-Bi sulphosalts, Pb-As and Bi sulphohalides, Cd, Pb, Tl halides, and an amorphous As-S compound. Sublimates are especially enriched in cadmium, thallium and iodine. Two new Cd-bearing sulphosalts Cd4PbBi12(S,Se)23 and CdPb4Bi6(S,Se)14 containing respectively 9 and 4 atomic% Cd were described. Tl occurs as three different halides. Seven phases contain iodine as a major or minor component; four of them additionally contain bromine. Crystal sizes, shapes and quantity within deposition intervals vary according to nucleation conditions. Mineral assemblages in natural fumarolic incrustations partly repeat the sequence observed in silica tubes.

Cupromolybdite, Cu3O(MoO4)2, a new fumarolic mineral from the Tolbachik volcano, Kamchatka Peninsula, Russia

Cupromolybdite is a new fumarolic mineral from the New Tolbachik scoria cones of Tolbachik volcano, Kamchatka Peninsula, Russia. Cupromolybdite forms prismatic crystals up to 150 μm in length or acicular crystals with a thickness and length of 1–5 μm and 100 μm, respectively. The acicular crystals of cupromolybdite are typically combined in radiating aggregates. The mineral is associated with piypite, fedotovite, vergasovaite, hematite, magnetite, aphthitalite, langbeinite, palmierite, As-bearing orthoclase, lammerite, klyuchevskite, alumoklyuchevskite, euchlorine, lyonsite, pseudolyonsite, averievite, rutile and native gold. Cupromolybdite is honey-yellow or brown, and its acicular crystals are bright yellow. The mineral has yellow or light brown streak and an adamantine lustre. Cupromolybdite is brittle, and its fracture ranges from uneven to splintery. The calculated density is 4.512 g/cm 3 . The reflectance values ( R 1 and R 2 , %) in air for the four COM wavelengths are 14.95, 16.3 (470 nm), 13.4, 14.85 (546 nm), 12.73, 14.16 (589 nm), and 12.15, 13.5 (650 nm). The chemical composition (the mean of 7 electron microprobe analyses) of cupromolybdite is: CuO 43.03, FeO 0.08, ZnO 0.53, MoO 3 54.48, SO 3 0.71, V 2 O 5 0.28, SiO 2 0.04, total 99.15 wt%, corresponding, on the basis of 9 O atoms, to (Cu 2.83 Zn 0.03 Fe 0.01 ) ∑2.87 (Mo 1.98 S 0.05 V 0.02 ) ∑2.05 O 9 . The simplified formula of cupromolybdite is Cu 3 O(MoO 4 ) 2 = Cu 3 Mo 2 O 9 . Cupromolybdite is orthorhombic, space group Pnma , a = 7.6638(1), b = 6.8670(1), c = 14.5554(2) A, V = 766.01(2) A 3 and Z = 4. The strongest powder-diffraction lines [ d in A ( I ) ( hkl )] are: 7.312 (67) (002); 3.518 (55) (113); 3.436 (100) (020); 3.301 (99) (210, 104); 3.065 (79) (121); 2.556 (62) (220); 2.506 (66) (301, 024). The crystal structure was solved from single-crystal data and refined to R = 0.0314. Cupromolybdite is a natural analogue of the synthetic compound Cu 3 Mo 2 O 9 and the S-free analogue of vergasovaite, Cu 3 O[(Mo,S)O 4 ][SO 4 ]. The crystal structure of cupromolybdite contains strings of corner-shared Cu(1)O 6 octahedra elongated in the [010] direction. In cupromolybdite, the Cu(2)O 5 square pyramids and the Cu(3)O 6 distorted octahedra are linked to the Cu(1)O 6 octahedra of the strings by edges and to the MoO 4 and (Mo,S)O 4 tetrahedra by vertices. A minor admixture of S is concentrated in one of two independent tetrahedral positions. Cupromolybdite is named for its chemical composition.

Pseudolyonsite, Cu3(VO4)2, a new mineral species from the Tolbachik volcano, Kamchatka Peninsula, Russia

Pseudolyonsite, ideally Cu 3 (VO 4 ) 2 , is a new mineral from the medium-temperature fumaroles of the New Tolbachik scoria cones, Tolbachik volcano, Kamchatka Peninsula, Russia. It occurs as needles that are 5–20 μm across and up to 0.5 mm in the length, which sometimes produce parallel intergrowths, sprays or openwork clusters up to 2 mm. Associated minerals are: piypite, hematite, magnetite, lyonsite, aphthitalite, palmierite, langbeinite, filatovite, lammerite, vergasovaite, rutile and native gold. Pseudolyonsite is dark red with a brownish tint to black, translucent to opaque, with a reddish-brown streak and adamantine to semi-metallic lustre. The mineral is brittle, but thin long needles are flexible. The fracture is conchoidal, and no cleavage was observed. The calculated density is 4.749 g/cm 3 . In reflected light in air the mineral is grey with a weak bluish tint, non-pleochroic, has distinct anisotropy and ubiquitous red to orange internal reflections. The reflectance values (R 1 and R 2 , %) in air for the four COM wavelengths are, respectively, 17.05, 19.6 (470 nm); 16.1, 18.15 (546 nm); 15.85, 17.7 (589 nm); and 15.55, 17.4 (650 nm). Four electron probe (EDS) analyses produced the following mean values: V 2 O 5 40.37, CuO 48.83, ZnO 7.60, MoO 3 1.89, and SiO 2 0.14, total 98.83 wt%, which corresponds, on the basis of 8 O atoms, to (Cu 2.58 Zn 0.44 ) ∑3.02 (V 1.88 Mo 0.06 Si 0.02 ) ∑1.96 O 8 . The idealised formula is Cu 3 (VO 4 ) 2 . Pseudolyonsite is monoclinic: P 2 1 / c , a = 6.2695(4), b = 8.0195(3), c = 6.3620(3) A, β = 111.96(1)°, V = 296.66(3) A 3 , Z = 2. The strongest powder X-ray diffraction lines [ d in A (I) ( hkl )] are: 4.70 (60) (110); 3.30 (79) (021, 120); 3.22 (87) (111); 3.18 (34) (−121, −102); 2.894 (74) (200, −211); 2.761 (100) (012); 2.479 (59) (−212, −122); 2.419 (67) (031, 130). The crystal structure was solved from single-crystal data and refined to R = 0.0444. Pseudolyonsite is isostructural with synthetic monoclinic Cu 3 (VO 4 ) 2 . The crystal structure of pseudolyonsite contains corrugated octahedral layers formed by the chains of edge-shared, distorted Cu(2)-octahedra running along the c axis and connected to each other by distorted Cu(1)-octahedra. The octahedra of both types contain Cu and subordinate Zn, and they are typically Jahn-Teller-distorted. Adjacent octahedral layers are connected to each other by VO 4 tetrahedra. Pseudolyonsite is dimorphous with triclinic mcbirneyite. The name pseudolyonsite comes from its close visual similarity to another vanadate mineral, lyonsite, Cu 3 Fe 3+ 4 (VO 4 ) 6 . Both the mineral and its name have been approved by the IMA CNMNC (IMA No. 2009-062).

Starovaite, KCu5O(VO4)3, a new mineral from fumarole sublimates of the Tolbachik volcano, Kamchatka, Russia

The new mineral species starovaite, ideally KCu 5 O(VO 4 )3, has been found in the sublimates of the Yadovitaya fumarole at the Second scoria cone of the Northern Breach of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. The mineral is associated with lammerite, hematite, palmierite, tenorite, piypite, rutile, orthoclase, lyonsite, pseudolyonsite, lammerite-β, langbeinite, calciolangbeinite, and cupromolybdite. Starovaite occurs as prismatic crystals up to 3 × 6 × 20 μm or divergent long-prismatic crystals up to 1 × 3 × 70 μm. The crystals are combined in sprays, sheaf-like aggregates or crusts up to 0.3 × 0.5 mm overgrowing lammerite. Starovaite is golden brown to reddish brown with a semi-metallic luster. The mineral is brittle, VHN is 182 (range 165–195) kg mm −2 . Cleavage and parting were not observed, fracture is uneven. D (calc.) = 4.54 g cm −3 . In reflected light, starovaite is grey with a brownish hue. Bireflectance is weak, internal reflections are distinct red-brown, anisotropy is weak. The reflectance values [ R 1 −R 2 , % (λ, nm)] are: 14.2–12.45 (470), 13.2–11.6 (546), 13.0–11.4 (589), 12.6–11.35 (650). The chemical composition (wt%, electron microprobe data) is: K 2 O 4.90, CaO 0.04, PbO 1.29, CuO 48.20, ZnO 5.59, Al 2 O 3 0.08, Fe 2 O 3 0.10, P 2 O 5 0.05, As 2 O 5 4.49, V 2 O 5 31.89, SO 3 0.19, MoO 3 2.34, total 99.16. The empirical formula calculated on the basis of 13 O apfu is: (K 0.76 Pb 0.04 Ca 0.01 ) Σ0.81 (Cu 4.45 Zn 0.51 Al 0.01 Fe 0.01 ) Σ4.98 (V 2.58 As 0.29 Mo 0.12 S 0.02 P 0.01 ) Σ3.02 O 13 . Starovaite is triclinic, P –1, a = 6.08(4), b = 8.26(5), c = 10.71(6) A, α = 97.8(1), β = 92.4(1), γ = 90.4(1)°, V = 532(2) A 3 , and Z= 2. The strongest reflections of the X-ray powder diffraction pattern [ d , A ( I , %) (hkl)] are: 10.62 (32) (001); 8.18 (46) (010); 3.047 (41) (022, 200,12-2); 2.745 (47) (2-1-1, 03-1); 2.526 (100) (031, 2-12, 2-1-2, 023, 1-31,13-1); 2.322 (98) (03-3, 21-3, 221, 22-2); 1.867 (23) (302); 1.410 (23) (24-5, 053,41-3, 03-7). Starovaite is a natural analogue of synthetic KCu 5 O(VO 4 )3. The mineral is named in honour of the Russian crystallographer and crystal chemist Galina L. Starova (b. 1946) for her contributions to the crystal chemistry of minerals from the Tolbachik fumaroles.

Yaroshevskite, Cu9O2(VO4)4Cl2, a new mineral from the Tolbachik volcano, Kamchatka, Russia

Abstract A new mineral, yaroshevskite, ideally Cu9O2(VO4)4Cl2, occurs in sublimates collected from the Yadovitaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with euchlorine, fedotovite, hematite, tenorite, lyonsite, melanothallite, atlasovite, kamchatkite and secondary avdoninite, belloite and chalcanthite. Yaroshevskite forms isolated prismatic crystals, up to 0.1 × 0.15 × 0.3 mm in size, on the surface of euchlorine crusts. The mineral is opaque and black, with a reddish black streak and lustre between metallic and adamantine. Yaroshevskite is brittle, no cleavage was observed and the fracture is uneven. The Mohs hardness is ~3½ (corresponding to a mean VHN micro-indentation hardness of 172 kg mm-2) and the calculated density is 4.26 g cm-3. In reflected light, yaroshevskite is grey with a weak bluish hue. Pleochroism, internal reflections and bireflectance were not observed. Anisotropy is very weak. The composition (wt.%) determined by electron microprobe is: CuO 61.82, ZnO 0.53, Fe2O3 0.04, V2O5 31.07, As2O5 0.32, MoO3 1.56, Cl 6.23, O=Cl2 -1.41; total 100.16. The empirical formula, calculated on the basis of 20 (O + Cl) anions is (Cu8.80Zn0.07Fe0.01)Σ8.88 (V3.87Mo0.12As0.03)Σ4.02O18.01Cl1.99. Yaroshevskite is triclinic, space group P1̅, a = 6.4344(11), b = 8.3232(13), c = 9.1726(16) Å , α = 105.338(14), β = 96.113(14), γ = 107.642(1)º, V = 442.05(13) Å3 and Z = 1. The nine strongest reflections in the X-ray powder pattern [dobs in Å (I)(hkl)] are as follows: 8.65(100)(001); 6.84(83)(01̅1); 6.01(75)(100); 5.52(60)(1̅01); 4.965(55)(011); 4.198(67)(11̅1̅); 4.055(65)(110); 3.120(55)(021); 2.896(60)(211̅,003,2̅20). The crystal structure was solved by direct methods from single-crystal X-ray diffraction data and refined to R = 0.0737. The yaroshevskite structure is unique. It is based on corrugated layers made up of chains of edge-sharing flat squares with central Cu2+ cations [Cu(1), Cu(4) and Cu(5)]; neighbouring chains are connected via groups consisting of three Cu2+-centred squares [two Cu(3) and Cu(6)]. Neighbouring layers are connected via pairs of Cu(2)O4Cl five-coordinate polyhedra and isolated VO4 tetrahedra. The structure of yaroshevskite can also be considered in terms of oxygen-centred tetrahedra: O(7)Cu4 tetrahedra are connected via common Cu(4) and Cu(5) vertices to form pyroxene-like chains [O2Cu6]∞. In this context, the structural formula can be written Cu3[O2Cu6][VO4]4Cl2. The mineral name honours the Russian geochemist Alexei A. Yaroshevsky (b. 1934) of Moscow State University.

First occurrence of iodine in natural sulfosalts : The case of mutnovskite, Pb2AsS3(I,Cl,Br), a new mineral from the Mutnovsky volcano, Kamchatka Peninsula, Russian Federation

Abstract 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) Å3, 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 boccur 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.

Calciolangbeinite, K2Ca2(SO4)3, a new mineral from the Tolbachik volcano, Kamchatka, Russia

Abstract The new mineral calciolangbeinite, ideally K2Ca2(SO4)3, is the Ca-dominant analogue of langbeinite. It occurs in sublimates at the Yadovitaya fumarole on the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure eruption, Tolbachik volcano, Kamchatka, Russia. The mineral is associated with langbeinite, piypite, hematite, rutile, pseudobrookite, orthoclase, lyonsite, lammerite, cyanochroite and chlorothionite. Calciolangbeinite occurs as tetrahedral to pseudooctahedral crystals, which are bounded by {111} and {111̅}, and as anhedral grains up to 1 mm in size, aggregated into clusters up to 2 mm across, and forming crusts covering areas of up to 1.5 6 1.5 cm on the surface of volcanic scoria. Late-stage calciolangbeinite occurs in complex epitaxial intergrowths with langbeinite. Calciolangbeinite is transparent and colourless with white streak and vitreous lustre. Its Mohs’ hardness is 3-3½. It is brittle, has a conchoidal fracture and no obvious cleavage. The measured and calculated densities are D meas = 2.68(2) and D calc = 2.74 g cm-3, respectively. Calciolangbeinite is optically isotropic with n = 1.527(2). The chemical composition of the holotype specimen is Na2O 0.38, K2O 21.85, MgO 6.52, CaO 16.00, MnO 0.27, FeO 0.08, Al2O3 0.09, SO3 55.14, total 100.63 wt.%. The empirical formula, calculated on the basis of twelve oxygen atoms per formula unit, is K2.01(Ca1.24Mg0.70Na0.05Mn0.02Fe0.01Al0.01)S 2.03S3.00O12. Calciolangbeinite is cubic, space group P213, a = 10.1887(4) Å, V = 1057.68(4) Å3 and Z = 4. The strongest reflections in the X-ray powder pattern [listed as (d,Å(I)(hkl)] are 5.84(8)(111); 4.54(9)(120); 4.15(27)(211); 3.218 (100) (310, 130); 2.838 (8) (230, 320), 2.736 (37) (231, 321), 2.006 (11) (431, 341) , 1.658(8)(611,532,352). The crystal structure was refined from single-crystal X-ray diffraction data to R = 0.0447. The structure is based on the langbeinite-type three-dimensional complex framework, which is made up of (Ca,Mg)O6 octahedra (Ca and Mg are disordered) and SO4 tetrahedra. Potassium atoms occupy two sites in voids in the framework; K(1) cations are located in ninefold polyhedra whereas K(2) cations are sited in significantly distorted octahedra. Calciolangbeinite and langbeinite are isostructural and form a solid-solution series.

A new Cu-rich variety of lyonsite from fumarolic sublimates of the Tolbachik volcano (Kamchatka, Russia) and its crystal structure

A new Cu-rich variety of lyonsite has been found from fumarolic sublimates of the Tolbachik volcano (Kamchatka, Russia). The empirical formula is Cu4.33Fe2.373+Ti0.26Al0.26Zn0.07(V5.85As0.07Mo0.07P0.01S0.01)O24. The crystal structure was studied on single crystal using synchrotron radiation, R = 0.0514. The mineral is orthorhombic, Pnma, a = 5.1736(7), b =10.8929(12), c = 18.220(2) Å, V = 1026.8(2) Å3, and Z = 2. The structural formula is (Cu0.6Ti0.3Al0.3Fe0.23+□0.6)Σ2Cu2(Fe2.23+Cu1.8)Σ4(V5.8As0.1Mo0.1)Σ6O24. It is proposed to recast the simplified formula of lyonsite as Cu3+x(Fe4−2x3+Cu2x)(VO4)6, where 0 ≤ x ≤ 1.

Tazieffite, Pb20Cd2(As,Bi)22S50Cl10, a new chloro-sulfosalt from Mutnovsky volcano, Kamchatka Peninsula, Russian Federation

Abstract 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, needleshaped 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.

Krasheninnikovite, KNa2CaMg(SO4)3F, a new mineral from the Tolbachik volcano, Kamchatka, Russia

Abstract 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 pseudoframework 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.