Kasatkinite, Ba2Ca8B5Si8O32(OH)3 · 6H2O6, a new mineral from the Bazhenovskoe deposit, the Central Urals, Russia

A new mineral, kasatkinite, Ba₂Ca₈B₅Si₈O₃₂(OH)₃ · 6H₂O, has been found at the Bazhenovskoe chrysotile asbestos deposit, the Central Urals, Russia in the cavities in rhodingite as a member of two assemblages: (l) on prehnite, with pectolite, calcite, and clinochlore; and (2) on grossular, with diopside and pectolite. Kasatkinite occurs as spherulites or bunches up to 3 mm in size, occasionally combined into crusts. Its individuals are acicular to hair-like, typically split, with a polygonal cross section, up to 0.5 mm (rarely, to 6 mm) in length and to 20 μm in thickness. They consist of numerous misoriented needle-shaped subindividuals up to several dozen μm long and no more than 1 μm thick. Kasatkinite individuals are transparent and colorless; its aggregates are snow white. The luster is vitreous or silky. No cleavage was observed; the fracture is uneven or splintery for aggregates. Individuals are flexible and elastic. The Mohs’ hardness is 4–4.5. D _meas = 2.95(5), D _calc = 2.89 g/cm³. Kasatkinite is optically biaxial (+), α = 1.600(5), β = 1.603(2), γ = 1.626(2), 2V _meas = 30(20)°, 2V _calc = 40°. The IR spectrum is given. The ¹¹B MAS NMR spectrum shows the presence of BO₄ in the absence of BO₃ groups. The chemical composition of kasatkinite (wt %; electron microprobe, H₂O by gas chromatography) is as follows: 0.23 Na₂O, 0.57 K₂O, 28.94 CaO, 16.79 BaO, 11.57 B₂O₃, 0.28 Al₂O₃, 31.63 SiO₂, 0.05 F, 9.05 H₂O, ?0.02 ?O=F₂; the total is 99.09. The empirical formula (calculated on the basis of O + F = 41 apfu, taking into account the TGA data) is: Na_0.11K_0.18Ba_1.66Ca_7.84B_5.05Al_0.08Si_8.00O_31.80(OH)_3.06F_0.04 · 6.10H₂O. Kasatkinite is monoclinic, space group P2₁/c, P2/c, or Pc; the unit-cell dimensions are a = 5.745(3), b = 7.238(2), c = 20.79 (1) Å, β = 90.82(5)°, V = 864(1) ų, Z = 1. The strongest reflections (d Å–I[hkl]) in the X-ray powder diffractions pattern are: 5.89–24[012], 3.48–2.1[006], 3.36–24[114]; 3.009–100[ $12\bar 1$ , 121, $10\bar 6$ ], 2.925–65[106, $12\bar 2$ , 122], 2.633–33[211, 124], 2.116–29[ $13\bar 3$ , 133, 028]. Kasatkinite is named in honor of A.V. Kasatkin (b. 1970), a Russian amateur mineralogist and mineral collector who has found this mineral. Type specimen is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow.     

Hillesheimite, (K,Ca,□)2(Mg,Fe,Ca,□)2[(Si,Al)13O23(OH)6](OH) · 8H2O, a new phyllosilicate mineral of the Günterblassite group

A new mineral, hillesheimite, has been found in the Graulai basaltic quarry, near the town of Hillesheim, the Eifel Mountains, Rhineland-Palatinate (Rheinland-Pfalz), Germany. It occurs in the late assemblage comprising nepheline, augite, fluorapatite, magnetite, perovskite, priderite, götzenite, lamprophyllite-group minerals, and åkermanite. Colorless flattened crystals of hillesheimite reaching 0.2 × 1 × 1.5 mm in size and aggregates of the crystals occur in miarolitic cavities in alkali basalt. The mineral is brittle, with Mohs’ hard-ness 4. Cleavage is perfect parallel to (010) and distinct on (100) and (001). D _calc = 2.174 g/cm³, D _meas = 2.16(1) g/cm³. IR spectrum is given. Hillesheimite is biaxial (?), α = 1.496(2), β = 1.498(2), γ = 1.499(2), 2V _meas = 80°. The chemical composition (electron microprobe, mean of 4 point analyses, H₂O determined from structural data, wt %) is as follows: 0.24 Na₂O, 4.15 K₂O, 2.14 MgO, 2.90 CaO, 2.20 BaO, 2.41 FeO, 15.54 Al₂O₃, 52.94 SiO₂, 19.14 H₂O, total is 101.65. The empirical formula is: K_0.96Na_0.08Ba_0.16Ca_0.56Mg_0.58Fe _0.37 ²⁺ [Si_9.62Al_3.32O₂₃(OH)₆][(OH)_0.82(H₂O)_0.18] · 8H₂O. The crystal structure has been determined from X-ray single-crystal diffraction data, R = 0.1735. Hillesheimite is orthorhombic, space group Pmmn, the unit-cell dimensions are: a = 6.979(11), b = 37.1815(18), c = 6.5296(15) Å; V=1694(3) ų, Z = 2. The crystal structure is based on the block [(Si,Al)₁₃O₂₅(OH)₄] consisting of three single tetrahedral layers linked via common vertices and is topologically identical to the triple layers in günterblassite and umbrianite. The strong reflections [d Å (I %)] in the X-ray powder diffraction pattern are: 6.857(58), 6.545(100), 6.284(53), 4.787(96), 4.499(59), 3.065(86), 2.958(62), 2.767(62). The mineral was named after its type locality. Type specimens are deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, registration number 4174/1.     

Alumovesuvianite,Ca19Al(Al,Mg)12Si18O69(OH)9, a new vesuvianite-group member from the Jeffrey mine,asbestos, Estrie region,Québec,Canada

Mineralogy and Petrology - Alumovesuvianite (IMA 2016–014), ideally Ca19Al(Al,Mg)12Si18O69(OH)9, is a new vesuvianite-group member found in the rodingite zone at the contact of a gabbroid...     

The geochemical and genetic role of organic substances in postmagmatic derivatives of alkaline plutons

Solid bituminous substances (SBS) are common components of the late hydrothermal mineral assemblages of peralkaline pegmatites. SBS are formed in a reductive setting as a result of progressive sorption of minor carbon-bearing molecules (CO, CO₂, CH₄, C₂H₆, C₂H₄, etc.), their polymerization, transformation into aromatic compounds (reformation), and selective oxidation on microporous zeolite-like Ti-, Nb-, and Zrsilicates serving as sorbents and catalysts. The oxygen-bearing aromatic compounds with hydrophile functional groups (−OH, −C=O, −COOH, −COO) act as complexing agents with respect to Th, REE, U, Zr, Ti, Nb, Ba, Sr, Ca, resulting in transfer of these bitumenophile elements under low-temperature hydrothermal conditions in the form of water-soluble macroassociates of the micelle type. Th, REE, and to a lesser extent, U, Zr, Ti, and Nb concentrate at the late stage of the hydrothermal process as microphases impregnating SBS or macroscopic segregations of Th and REE minerals. At the final stage, homogeneous SBS break down into organic (partly together with Ca, Sr, Ba, and Pb) and mineral (with Th, Ln, Y, Ti, Nb, Ca, Na, K, Si) microphases.     

On the problem of the formation and geochemical role of bituminous matter in pegmatites of the Khibiny and Lovozero alkaline massifs, Kola Peninsula, Russia

Solid bituminous matter (SBM) typically occurs in the late hydrothermal assemblages of pegmatites of the Khibiny and Lovozero massifs, being confined to a microporous framework Ti-, Nb-, and Zr-silicates, which are sorbents of small molecules and efficient catalysts of the polymerization, reforming, and selective oxidation of organic matter. Bituminous matter from the pegmatites of the Lovozero Massif typically have elevated contents of aliphatic hydrocarbons, sulfur, and sodium, but are depleted in oxygen and trace elements. SBM from the pegmatites of the Khibiny Massif are depleted in sulfur and enriched in oxygen-bearing derivatives of polycyclic aromatic hydrocarbons. Being complexing agents for Th, REE, Ba, Sr, and Ca, they play a key role in the transfer and accumulation of Th and in the accumulation of alkali earth and rare earth elements during the hydrothermal stage of mineral formation. Oxidized SBM bearing rare and alkali earth elements are complex microheterogenous systems, which contain mineral (Th silicates, calcite, etc.), metalorganic (with REE, Ca, Sr, Ba), and predominantly organic phases formed by the exsolution of initial metalorganic material with decreasing temperature.     

Chesnokovite,Na<Subscript>2</Subscript>[SiO<Subscript>2</Subscript>(OH)<Subscript>2</Subscript>] · 8H<Subscript>2</Subscript>O,the first natural sodium orthosilicate from the Lovozero alkaline pluton,Kola Peninsula: Description and crystal structure of a new mineral species

Chesnokovite, a new mineral species, is the first natural sodium orthosilicate. It has been found in an ussingite vein uncovered by underground mining at Mt. Kedykverpakhk, Lovozero alkaline pluton, Kola Peninsula, Russia. Natrolite, sodalite, vuonnemite, steenstrupine-(Ce), phosinaite-(Ce), natisite, gobbinsite, villiaumite, and natrosilite are associated minerals. Chesnokovite occurs as intergrowths with natrophospate in pockets up to 4 × 6 × 10 cm in size consisting of chaotic segregations of coarse lamellar crystals (up to 0.05 × 1 × 2 cm in size) flattened along [010]. The crystals are colorless and transparent. The aggregates are white to pale brownish yellowish, with a white streak and a vitreous luster. The cleavage is perfect parallel to (010) and distinct to (100) and (001). The fracture is stepped. The Mohs’ hardness is 2.5. The measured density is 1.68 g/cm³; the density calculated on the basis of an empirical formula is 1.60 g/cm³ and 1.64 g/cm³ on the basis of an idealized formula. The new mineral is optically biaxial, positive, α = 1.449, β = 1.453, γ = 1.458, 2V _meas = 80°, and Z = b. The infrared spectrum is given. The chemical composition (Si determined with electron microprobe; Na, K, and Li, with atomic emission analysis; and H₂O, with the Alimarin method) is as follows, wt %: 21.49 Na₂O, 0.38 K₂O, 0.003 Li₂O, 21.42 SiO₂, 54.86 H₂O, total is 98.153. The empirical formula calculated on the basis of O₂(OH)₂ is as follows: (Na_1.96K_0.02)_Σ1.98Si_1.005O₂(OH)₂ · 7.58H₂O. The simplified formula (Z = 8) is Na₂[SiO₂(OH)₂] · 8H₂O. The new mineral is orthorhombic, and the space group is Ibca. The unit-cell dimensions are: a = 11.7119, b = 19.973, c = 11.5652 Å, and V = 2299.0 ų. The strongest reflections in the X-ray powder pattern [d, Å (I, %)(hkl)] are: 5.001(30)(211), 4.788(42)(022), 3.847(89)(231), 2.932(42)(400), 2.832(35)(060), 2.800(97)(332, 233), and 2.774(100)(341, 143, 114). The crystal structure was studied using the Rietveld method, R _p = 5.77, R _wp = 7.77, R _B = 2.07, and R _F = 1.74. The structure is composed of isolated [SiO₂(OH)₂] octahedrons and the chains of edge-shared [Na[H₂O)₆] octahedrons. The Si and Na polyhedrons are linked only by H-bonds, and this is the cause of the low stability of chesnokovite under atmospheric conditions. The new mineral is named in memory of B.V. Chesnokov (1928–2005), an outstanding mineralogist. The type material of chesnokovite is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow.     

Natisite,Na2TiSiO5, an Indicator Mineral of Hyperagpaitic Hydrothermal Assemblages in the Lovozero and Khibiny Alkaline Plutons,Kola Peninsula: Occurrence,Crystal Chemistry,and Genetic Features

Geology of Ore Deposits - Natisite, a natural tetragonal (P4/nmm) modification of Na2TiSiO5 = Na2TiO(SiO4) is an abundant indicator mineral of relatively low-temperature (no higher than...     

Lazurite: Validation as a Mineral Species with the Formula Na7Ca(Al6Si6O24)(SO4) $${\text{S}}_{3}^{{\bullet - }}$$ ⋅H2O and New Data

Geology of Ore Deposits - The status of lazurite as a valid mineral species has been confirmed. The neotype specimen from the Malaya Bystraya gem lazurite deposit, Baikal Lake area has been studied...     

Cymrite as an indicator of high barium activity in the formation of hydrothermal rocks related to carbonatites of the Kola Peninsula

Cymrite, BaAl₂Si₂O₈ · nH₂O, is a rare mineral formed during low-grade dynamothermal metamorphism (T = 250–300°C, P = 1–3 kbar). Cymrite has been described from many metasedimentary ores and hydrothermal rocks. In carbonatites, it has been found for the first time. Cymrite has been identified in the Kovdor and Seblyavr massifs, Kola Peninsula. In Kovdor, this mineral has been described from one of the hydrothermal veins cutting the pyroxenite-melilitite-ijolite complex at the Phlogopite deposit; cymrite is associated with thomsonite, calcite, and stivensite. In the Seblyavr pluton, cymrite occurs in thin veins of calcite carbonatite that cut pyroxenite contacting with ijolite. Cymrite from the Seblyavr pluton is associated with calcite, natrolite, pyrite, and chalcopyrite. The mineral is optically negative and uniaxial, with extinction parallel to elongation; ω ～ 1.607(1). According to X-ray diffraction data, cymrite from Seblyavr is monoclinic, space group P1m1; unit-cell dimensions are: a = 5.33, b = 36.96, c = 7.66 Å, β = 90°, V = 1510.55 ų. According to the results of IR spectroscopy, in the series of samples from different massifs (in the running order Kovdor-Voishor-Seblyavr), the double-layer deformation is enhanced and accompanied by a decrease in the Si-O-Si angle and weakening of hydrogen bonds of interlayer water. The empirical formulas of cymrite calculated from electron microprobe analyses are Ba_0.93–0.95Ca_0.01–0.02K_0.00–0.05Na_0.02–0.04Al_1.97–2.01Si_1.99–2.03O₈(H₂O) and Ba_1.00–1.02Ca_0.00–0.01Sr_0.00–0.01Fe_0.00–0.01Al_1.94–2.00Si_1.98–2.03O₈(H₂O) at Seblyavr and Kovdor, respectively. Cymrite from the carbonatite massifs of the Kola Peninsula was formed under hydrothermal conditions at low temperature (200–300°C), high activity of Ba and Si, and high water pressure. At Kovdor, the mineral crystallized directly from the residual solution enriched in Ba. The sequence of mineral deposition is as follows: thomsonite-cymrite-calcite-stevensite. Cymrite from the Seblyavr pluton is a product of hydrothermal alteration of primary Na-K-Ba silicates of ijolite: nepheline, feldspar, and probably celsian. Natrolite replaces cymrite indicating high alkalinity of late hydrothermal fluids.