Vigrishinite, Zn2Ti4 − x Si4O14(OH,H2O,□)8, a new mineral from the Lovozero alkaline complex, Kola Peninsula, Russia

A new mineral vigrishinite, epistolite-group member and first layer titanosilicate with species-defining Zn, was found at Mt. Malyi Punkaruaiv, in the Lovozero alkaline complex, Kola Peninsula, Russia. It occurs in a hydrothermally altered peralkaline pegmatite and is associated with microcline, ussingite, aegirine, analcime, gmelinite-Na, and chabazite-Ca. Vigrishinite forms rectangular or irregularly shaped lamellae up to 0.05 × 2 × 3 cm flattened on [001]. They are typically slightly split and show blocky character. The mineral is translucent to transparent and pale pink, yellowish-pinkish or colorless. The luster is vitreous. The Mohs’ hardness is 2.5–3. Vigrishinite is brittle. Cleavage is {001} perfect. D _meas = 3.03(2), D _calc = 2.97 g/cm³. The mineral is optically biaxial (?), α = 1.755(5), β = 1.82(1), γ = 1.835(8), 2V _meas = 45(10)°, 2V _calc = 50°. IR spectrum is given. The chemical composition (wt %; average of 9 point analyses, H₂O is determined by modified Penfield method) is as follows: 0.98 Na₂O, 0.30 K₂O, 0.56 CaO, 0.05 SrO, 0.44 BaO, 0.36 MgO, 2.09 MnO, 14.39 ZnO, 2.00 Fe₂O₃, 0.36 Al₂O₃, 32.29 SiO₂, 29.14 TiO₂, 2.08 ZrO₂, 7.34 Nb₂O₅, 0.46 F, 9.1 H₂O, ?0.19 O=F₂, total is 101.75. The empirical formula calculated on the basis of Si + Al = 4 is: H_7.42(Zn_1.30Na_0.23Mn_0.22Ca_0.07Mg_0.07K_0.05Ba_0.02)_Σ1.96(Ti_2.68Nb_0.41Fe _0.18 ³⁺ Zr_0.12)_Σ3.39(Si_3.95Al_0.05)_{Σ4 20.31}F_0.18. The simplified formula is: Zn₂Ti_4?x Si₄O₁₄(OH,H₂O,□)₈ (x < 1). Vigrishinite is triclinic, space group P $\bar 1$ , a = 8.743(9), b = 8.698(9), c = 11.581(11)Å, α = 91.54(8)°, β = 98.29(8)°, γ = 105.65(8)°, V = 837.2(1.5) ų, Z = 2. The strongest reflections in the X-ray powder pattern (d, Å, ?I[hkl]) are: 11.7-67[001], 8.27-50[100], 6.94-43[0 $\bar 1$ 1, $\bar 1$ 10], 5.73–54[1 $\bar 1$ 1, 002], 4.17-65[020, $\bar 1$ $\bar 1$ 2, 200], and 2.861-100[3 $\bar 1$ 0, 2 $\bar 2$ 2, 004, 1 $\bar 3$ 1]. The crystal structure model was obtained on a single crystal, R = 0.171. Vigrishinite and murmanite are close in the structure of the TiSiO motif, but strongly differ from each other in part of large cations and H-bearing groups. Vigrishinite is named in honor of Viktor G. Grishin (b. 1953), a Russian amateur mineralogist and mineral collector, to pay tribute to his contribution to the mineralogy of the Lovozero Complex. The type specimen is deposited in the Fersman Mineralogical Museum of Russian Academy of Sciences, Moscow.     

Batagayite,CaZn2(Zn,Cu)6(PO4)4(PO3OH)3·12H2O,a new phosphate mineral from Këster tin deposit (Yakutia,Russia): occurrence and crystal structure

Mineralogy and Petrology - Batagayite, CaZn2(Zn,Cu)6(PO4)4(PO3OH)3·12H2O, is a new secondary phosphate mineral from the Këster deposit, Arga-Ynnykh-Khai massif, NE Yakutia, Russia. It is...     

Kobyashevite, Cu5(SO4)2(OH)6·4H2O, a new devilline-group mineral from the Vishnevye Mountains, South Urals, Russia

A new mineral kobyashevite, Cu₅(SO₄)₂(OH)₆·4H₂O (IMA 2011–066), was found at the Kapital’naya mine, Vishnevye Mountains, South Urals, Russia. It is a supergene mineral that occurs in cavities of a calcite-quartz vein with pyrite and chalcopyrite. Kobyashevite forms elongated crystals up to 0.2 mm typically curved or split and combined into thin crusts up to 1?×?2 mm. Kobyashevite is bluish-green to turquoise-coloured. Lustre is vitreous. Mohs hardness is 2½. Cleavage is {010} distinct. D(calc.) is 3.16 g/cm³. Kobyashevite is optically biaxial (?), α 1.602(4), β 1.666(5), γ 1.679(5), 2 V(meas.) 50(10)°. The chemical composition (wt%, electron-microprobe data) is: CuO 57.72, ZnO 0.09, FeO 0.28, SO₃ 23.52, H₂O(calc.) 18.39, total 100.00. The empirical formula, calculated based on 18 O, is: Cu_4.96Fe_0.03Zn_0.01S_2.01O_8.04(OH)_5.96·4H₂O. Kobyashevite is triclinic, $ P\overline{\,1 } $ , a 6.0731(6), b 11.0597(13), c 5.5094(6)?Å, α 102.883(9)°, β 92.348(8)°, γ 92.597(9)°, V 359.87(7)?ų, Z?=?1. Strong reflections of the X-ray powder pattern [d,Å-I(hkl)] are: 10.84–100(010); 5.399–40(020); 5.178–12(110); 3.590–16(030); 2.691–16(20–1, 040, 002), 2.653–12(04–1, 02–2), 2.583–12(2–11, 201, 2–1–1), 2.425–12(03–2, 211, 131). The crystal structure (single-crystal X-ray data, R?=?0.0399) сontains [Cu₄(SO₄)₂(OH)₆] corrugated layers linked via isolated [CuO₂(H₂O)₄] octahedra; the structural formula is CuCu₄(SO₄)₂(OH)₆·4H₂O. Kobyashevite is a devilline-group member. It is named in memory of the Russian mineralogist Yuriy Stepanovich Kobyashev (1935–2009), a specialist on mineralogy of the Urals.     

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.     

Niedermayrite, Cu4Cd(SO4)2(OH)6 · 4H2O, a new mineral from the Lavrion Mining District, Greece

Summary Niedermayrite, Cu₄Cd(SO₄)₂(OH)₆ · 4H₂O, is a new mineral discovered in 1995 in the Km3-area of the Lavrion mining district, Greece. It forms tiny euhedral plates, commonly intergrown as green crusts up to several cm² in size on a matrix consisting of a brecciated marble with sphalerite, chalcopyrite, galena, greenockite, hawleyite and pyrite. Associated secondary minerals are gypsum, malachite, chalcanthite, brochantite, hemimorphite, hydrozincite, aurichalcite, one unknown Cd-sulfate, monteponite and otavite. Niedermayrite is non-fluorescent and has a bluish-green colour with vitreous lustre, the streak is white. The crystals are brittle with perfect cleavage parallel {010}. Optics: biaxial (–) with n(calc.), n, and n =1.609, 1.642(2), and 1.661(2), respectively; orientation n//b. The calculated density is 3.292 gcm^–3. The most prominent form is {010}. Analysis by electron microprobe gives CdO 16.5, CuO 45.7, SO₃ 21.6, H₂O 16.2 wt.% (calc. to 100% sum) and the empirical formula Cu_4.29Cd_0.96S_2.01O_11.28 · 6.71 H₂O (based on 18 oxygens p.f.u.). By TGA an H₂O content of 18.9 wt.% was obtained. The ideal formula (confirmed by the crystal structure refinement) is Cu₄Cd(SO₄)₂(OH)₆ · 4H₂O with a theoretical H₂O content of 17.2 wt.%. The strongest lines in the X-ray powder diffraction pattern (Gandolfi camera, visually estimated I, refined lattice parameters a = 5.535(2), b = 21.947(9), c = 6.085(2) Å, = 91.98(3)°) are: (d_obs[Å]/I_obs/hkl) (11.02/90/0 2 0), (5.874/20/0 1 1), (5.496/100/0 4 0), (5.322/25/0 2 1), (4.079/50/0 4 1), (3.660/20/0 6 0), (3. 437/30/1 5 0), (3.243/40/1 4 1), (2.470/30/2 4 0), (2.425/20/1 4 –2), (2.205/20/2 6 0) and (1.897/20/1 8 2). The mineral is monoclinic, P2₁/m, Z = 2, a = 5.543(1) Å, b = 21.995(4) Å, c = 6.079(1) Å, = 92.04(3)°, V = 740.7(2) ų. The crystal structure was determined by single crystal X-ray methods and was refined to R1= 0.026, wR2 = 0.056. The structure of niedermayrite is characterized by ² [Cu₄(OH)₆O₂]^2– sheets of edgesharing Cu coordination octahedra parallel to (010) with attached SO₄ tetrahedra, and intercalated CdO₂(H₂O)₄ octahedra with a system of hydrogen bonds. Close relationships to the crystal structures of christelite and campigliaite exist. The new mineral is named for Dr. Gerhard Niedermayr, Naturhistorisches Museum Wien, Austria.

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Niedermayrit, Cu₄Cd(SO₄)₂(OH)₆ · 4H₂O, ein neues Mineral aus dem Bergbaugebiet Lavrion, Griechenland

Zusammenfassung Niedermayrit, Cu₄Cd(SO₄)₂(OH)₆ · 4H₂O, ist ein neues Mineral, das 1995 im Km3-Bereich des Bergbaugebietes Lavrion, Griechenland, gefunden wurde. Es bildet winzige gut ausgebildete Plättchen, häufig miteinander verwachsen in grünen Krusten bis zu mehreren cm² Größe. Die Matrix besteht aus brecciösem Marmor mit Sphalerit, Chalcopyrit, Galenit, Greenockit, Hawleyit und Pyrit. Sekundäre Begleitminerale sind Gips, Malachit, Chalcanthit, Brochantit, Hemimorphit, Hydrozincit, Aurichalcit, ein unbekanntes Cd-Sulfat, Monteponit und Otavit. Niedermayrit fluoresziert nicht, besitzt blaugrüne Farbe mit Glasglanz, der Strich ist weiß. Die Kristalle sind spröd mit perfekter Spaltbarkeit parallel {010}. Optik: biaxial (–) mit n(ber.), n, und n=1.609, 1.642(2), und 1.661(2); Orientierung n//b. Die berechnete Dichte beträgt 3.292 gcm^–3. Die auffallendste Flächenform ist {010}. Die chemische Analyse mittels Mikrosonde ergibt CdO 16.5, CuO 45.7, SO₃ 21.6, H₂O 16.2wt.% (ber. auf 100% Summe) und die empirische Formel Cu_4.29Cd_0.96S_2.01O_11.28 · 6.71 H₂O (basierend auf 18 Sauerstoffatomen pro Formeleinheit). Aus der TGA wurde ein H₂O Gehalt von 18.9 Gew.% erhalten. Die Idealformel (bestätigt durch die Kristallstrukturverfeinerung) ist Cu₄Cd(SO₄)₂(OH)₆ · 4H₂O bei einem theoretischen H₂O-Gehalt von 17.2 Gew.%. Die stärksten Linien im Pulverdiffraktogramm (Gandolfi Kamera, visuell geschätzte I, verfeinerte Gitterkonstanten a = 5.535(2), b = 21.947(9), c = 6.085(2) Å, = 91.98(3)°) sind: (d_obs[Å]/I_obs/hkl) (11.02/90/0 2 0), (5.874/20/0 1 1), (5.496/100/0 4 0), (5.322/25/0 2 1), (4.079/50/0 4 1), (3.660/20/0 6 0), (3.437/30/1 5 0), (3.243/40/1 4 1), (2.470/30/2 4 0), (2.425/20/1 4 –2), (2.205/20/2 6 0) und (1.897/20/1 8 2). Das Mineral ist monoklin, P2₁/m, Z = 2, a = 5.543(1) Å, b = 21.995(4) Å, c = 6.079(1) Å, = 92.04(3)°, V = 740.7(2) ų Die Kristallstruktur wurde mittels Einkristallröntgenmethoden bestimmt und zu R1 = 0.026, wR2 = 0.056 verfeinert. Die Struktur von Niedermayrit ist durch ² [Cu₄(OH)₆O₂]^2– Schichten von kantenverknüpften Cu-Koordinationsoktaedern parallel (010) gekennzeichnet mit damit verbundenen SO₄ Tetraedern und dazwischen befindlichen CdO₂(H₂O)₄ Oktaedem mit einem Wasserstoffbrückensystem. Es bestehen enge Beziehungen mit den Kristallstrukturen von Christelit und Campigliait. Das neue Mineral ist nach Dr. Gerhard Niedermayr, Naturhistorisches Museum Wien, Österreich, benannt.

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With 7 Figures     

Lammerite-β, Cu3(AsO4)2, a new mineral from fumaroles of the Great Fissure Tolbachik eruption, Kamchatka Peninsula, Russia

Lammerite-β, Cu₃(AsO₄)₂, occurs as a product of the post-eruption fumarole activity of the second cinder cone of the North breach of the Great Fissure Tolbachik eruption in 1975–1976, Kamchatka Peninsula, Russia. Sporadic light to dark green splinter-shaped grains are no larger than 0.15 mm in size. Cleavage is not observed. The mechanical admixture of finely dispersed hematite forms condensed brownish spots that are occasionally zonal relative to the contours of the lammerite-β grains. Associated minerals are euchlorine, piypite, alumoklyuchevskite, alarsite, and lammerite. Lammerite-β is brittle and transparent and has vitreous luster. The calculated density is 5.06 g/cm³. The mineral is not pleochroic, biaxial (+), α = 1.887(5), β = 1.936(5), γ = 2.01(1), 2V(calc.) = 80.9°; dispersion is strong, r < v. The new mineral is monoclinic, the space group is P2₁/c, a = 6.306(1), b = 8.643(1), c = 11.310(1) Å, β = 92.26(1)°, V = 615.9(1) ų, and Z = 4. Characteristic reflections in the X-ray powder diffraction pattern (I-d-hkl) are 100-2.83-004, 10-5.65-002, and 10-4.32-020. The chemical composition is as follows, wt %: 51.30 CuO, 0.32 ZnO, 49.12 As₂O₃, with a total of 100.74 wt %. The empirical and idealized formulas are Cu_3.00Zn_0.02As_1.99O₈ and Cu₃(AsO₄)₂, respectively.     

Britvinite, Pb15Mg9(Si10O28)(BO3)4(CO3)2(OH)12O2, a new mineral species from Långban, Sweden

Britvinite, a new mineral species, has been found in manganese ore at the Långban deposit, Bergslagen ore district, Filipstad, Värmland County, Sweden. Calcite, barytocalcite, brucite, cerussite, and hausmannite are associated minerals. Britvinite occurs as pale yellow to colorless transparent plates with a white streak up to 0.2 × 0.5 × 0.5 mm in size, which are flat parallel to {001}; the luster is adamantine. Thin lamellae are flexible, whereas thick ones are brittle; the Mohs hardness is 3. The cleavage is eminent parallel to {001}. The calculated density is 5.51 g/cm³. In the infrared spectrum of the new mineral, the bands of (OH)?, (CO₃)^2?, and (BO₃)^3? are recorded, whereas those corresponding to water molecules are absent. Britvinite is optically biaxial and negative, α = 1.896(2), β = 1.903(2), γ = 1.903(2), 2Vmeas = 20(10), Z≈c. Dispersion is strong, r<v. The chemical composition (electron microprobe; H₂O determined with the Alimarin method, CO₂, with selective sorption) is (wt %) 7.95 MgO, 71.92 PbO, 0.41 Al₂O₃, 12.77 SiO₂, 2.2 H₂O, 2.1 CO₂, 2.67 B₂O₃ (calculated on the basis of structural data); total 100.02. The empirical formula calculated on the basis of 59 anions (O + OH) (Z = 1) is as follows: Pb_14.75Mg_9.03Si_9.73Al_0.37O_30.76(BO₃)_3.51(CO₃)_2.18(OH)_11.7. The simplified formula (Z = 2) is Pb_{7 + x} Mg_4.5(Si₅O₁₄)(BO₃)₂(CO₃)(OH,O)₇ (x < 0.5). The crystal structure of britvinite has been studied on a single crystal at 173 K; R = 0.0547. The new mineral is triclinic, space group P $ \bar 1 Britvinite, a new mineral species, has been found in manganese ore at the L?ngban deposit, Bergslagen ore district, Filipstad, V?rmland County, Sweden. Calcite, barytocalcite, brucite, cerussite, and hausmannite are associated minerals. Britvinite occurs as pale yellow to colorless transparent plates with a white streak up to 0.2 × 0.5 × 0.5 mm in size, which are flat parallel to {001}; the luster is adamantine. Thin lamellae are flexible, whereas thick ones are brittle; the Mohs hardness is 3. The cleavage is eminent parallel to {001}. The calculated density is 5.51 g/cm³. In the infrared spectrum of the new mineral, the bands of (OH)−, (CO₃)²⁻, and (BO₃)³⁻ are recorded, whereas those corresponding to water molecules are absent. Britvinite is optically biaxial and negative, α = 1.896(2), β = 1.903(2), γ = 1.903(2), 2Vmeas = 20(10), Z≈c. Dispersion is strong, r<v. The chemical composition (electron microprobe; H₂O determined with the Alimarin method, CO₂, with selective sorption) is (wt %) 7.95 MgO, 71.92 PbO, 0.41 Al₂O₃, 12.77 SiO₂, 2.2 H₂O, 2.1 CO₂, 2.67 B₂O₃ (calculated on the basis of structural data); total 100.02. The empirical formula calculated on the basis of 59 anions (O + OH) (Z = 1) is as follows: Pb_14.75Mg_9.03Si_9.73Al_0.37O_30.76(BO₃)_3.51(CO₃)_2.18(OH)_11.7. The simplified formula (Z = 2) is Pb_{7 + x} Mg_4.5(Si₅O₁₄)(BO₃)₂(CO₃)(OH,O)₇ (x < 0.5). The crystal structure of britvinite has been studied on a single crystal at 173 K; R = 0.0547. The new mineral is triclinic, space group P ; the unit-cell dimensions are a = 9.3409(8), b = 9.3597(7), c = 18.8333(14) ?, α = 80.365(6)°, β = 75.816(6)°, γ = 59.870(5)°, V = 1378.74(19) ?³. The structure consists of alternating TOT stacks (containing octahedral brucite-like and discontinuous tetrahedral (Si₅O₁₄)_∞∞ layers) and multilayered [Pb_7.1(OH)_3.6(CO₃)(BO₃)_1.75(SiO₄)_0.25]_∞∞ blocks. The strongest reflections in the X-ray powder diffraction pattern [d, ? (I, %)(hkl)] are 18.1(100)(001), 3.39(30)(12, 14, 015), 3.02(90)(006, 130, 106, 20, 11), 2.698(70)(332, 134, 030, 1), 2.275(30)(008, 420, 424), 1.867(30)(446, 239, 2.1.10, 18), 1.766(40)(151, 31, 10, 453, 542, 512, 42), 1.519(40)(0.0.12). The mineral has been named in honor of Sergei Nikolaevich Britvin (b. 1965), a Russian mineralogist. The type material of britvinite is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow. The registration number is 3458/1. Original Russian Text ? N.V. Chukanov, O.V. Yakubovich, I.V. Pekov, D.I. Belakovsky, W. Massa, 2007, published in Zapiski Rossiiskogo Mineralogicheskogo Obshchestva, 2007, Pt CXXXVI, No. 6, pp. 18–25. The new mineral britvinite and its name were accepted by the Commission on New Minerals and Mineral Names, Russian Mineralogical Society, June 7, 2006, and approved by the Commission on New Minerals and Mineral Names, International Mineralogical Association, October 17, 2006.     

Orschallite,Ca3(SO3)2 · SO4 · 12H2O,a new calcium-sulfite-sulfate-hydrate mineral

Summary The new mineral orschallite, Ca₃(SO₃)₂SO₄ · 12H₂O, was found at the Hannebacher Ley near Hannebach, Eifel, Germany. Crystal structure analysis of the mineral, chemical analysis and water determination on synthetic material gave the composition Ca₃(SO₃)₂SO₄ · 12H₂O. The mineral crystallizes in space group with a = 11.350(1), c = 28.321(2) Å, V = 3159.7 ų, Z = 6, D_c = 1.87 Mg/m³, D_m = 1.90(3) Mg/m³. It is uniaxial positive with the optical constants = 1.4941, = 1.4960(4). The strongest lines in the powder pattern are (d-value (Å), I, hkl) 5.73, 100, 1 0 4/8.11, 80, 0 1 2/2.69, 80, 3 0 6/3.63, 60, 1 1 6/3.28, 40, 3 0 0. Refinement of the crystal structure led to a weighted residual of R_w = 0.043 for 600 observed reflections with I > 2(I) and 52 variable parameters.

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Orschallit, Ca₃(SO₃)₂SO₄ · 12H₂O, ein neues Kalzium-Sulfat-Sulfat-Hydrat-Mineral

Zusammenfassung Das neue Mineral Orschallit, Ca₃(SO₃)₂SO₄ · 12H₂O, wurde in der Hannebacher Ley bei Hannebach, Eifel, Deutschland gefunden. Eine Analyse der Kristallstruktur an einem Einkristall des natürlichen Materials, chemische Analyse und Wasserbestimmung an synthetischem Material ergaben die Zusammensetzung Ca₃(SO₃)₂SO₄ · 12H₂O. Das Mineral kristallisiert in der Raumgruppe mit a = 11.350(1), c = 28.321(2) Å, V = 3159.7 ų, Z = 6, D_c = 1.87 Mg/m³, D_m = 1.90(3) Mg/m³. Es ist optisch einachsig mit den optischen Konstanten = 1.4941, = 1.4960(4). Die stärksten Linien des Pulver-diagramms liegen bei (d-Wert (Å), I, hkl) 5.73, 100, 1 0 4/8.11, 80, 0 1 2/2.69, 80, 3 0 6/3.63, 60; 1 1 6/3.28, 40, 3 0 0. Die Verfeinerung der Kristallstruktur ergab einen gewichteten Residualwert R_w = 0.043 für 600 beobachtete Reflexe mit I > 2(I) und 52 variable Parameter.

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With 5 Figures     

Ferrotochilinite, 6FeS · 5Fe(OH)2, a new mineral from the Oktyabr’sky deposit, Noril’sk district, Siberia, Russia

A new mineral, ferrotochilinite, ideally 6FeS · 5Fe(OH)₂, was found at the Oktyabr’sky Mine, Oktyabr’skoe Cu-Ni deposit, Noril’sk, Krasnoyarsk krai, Siberia, Russia. It is associated with ferrovalleriite, magnetite and Fe-rich, chlorite-like phyllosilicate in the cavities of pentlandite-mooihoekite-cubanite ore with subordinate magnetite and chalcopyrite. Ferrotochilinite occurs as flattened on [001], prismatic to elongated lamellar crystals up to 0.1 × 0.5 × 3.2 mm, typically split and curved. Aggregates (up to 6.5 mm in size) are fanlike, rosette-like, or chaotic. Ferrotochilinite is dark bronze. The streak is black. The luster is moderately metallic. The Mohs’ hardness is ca. 1; VHN is 13 kg/mm². Cleavage is {001} perfect, micalike. Individuals are flexible, inelastic. D(calc) = 3.467 g/cm³. In reflected light, ferrotochilinite is gray, with the hue changing from pale beige to bluish; bireflectance is distinct. Anisotropy is distinct, with gray bluish to yellowish beige rotation colors. No internal reflections. Reflectance values [R _min-R _max, % (λ, nm)] are: 11.6–11.4 (470), 11.2–12.4 (546), 11.1–13.6 (589), 11.0–15.5 (650). The IR spectrum shows the presence of (OH) groups bonded with Fe cations and the absence of H₂O molecules. Chemical composition (wt %; electron probe; H content is calculated) is as follows: 0.02 Mg, 61.92 Fe, 0.03 Ni, 0.09 Cu, 19.45 S, 16.3 O, 1.03 H _calc; the total is 98.84. The empirical formula calculated on the basis of 6 S atoms is: Mg_0.01Fe_10.96Ni_0.005Cu_0.015S₆(OH)_10.07 = (Fe_5.98Cu_0.0015Ni_0.005)_Σ6S₆(OH)_9.80(Fe _4.89 ²⁺ Mg_0.01)_Σ4.90(OH)_9.80Fe _0.09 ³⁺ (OH)_0.27. Ferrotochilinite is monoclinic, space group is C2/m, Cm or C2, the unit-cell dimensions are: a = 5.463(5), b = 15.865(17), c = 10.825(12) Å, β = 93.7(1)°, V = 936(3) ų, Z = 2. The strongest reflections in the X-ray powder diffraction pattern (d, Å-I[hkl]) are: 10.83-13[001], 5.392-100[002], 3.281-7[023], 2.777-7[150], 2.696-12[004, $20\bar 1$ ], 2.524-12[ $22\bar 1$ , $20\bar 2$ ], 2.152-8[134, 153], 1.837-11[135, $17\bar 3$ ]. Ferrotochilinite is a structural analog of tochilinite, with Fe²⁺ instead of Mg in the hydroxide part. The type specimen is deposited in Fersman Mineralogical Museum of Russian Academy of Sciences, Moscow.     

Mineral chemistry of columbite–tantalite from spodumene pegmatites of Kolmozero,Kola Peninsula (Russia)

Compositional variation (results of electron microprobe analyses and mass-spectrometry analyses) of columbite-group minerals (CGM) from fully differentiated albite–spodumene pegmatites at Kolmozero in the Kola Peninsula is evaluated. Concentric zoning, typical of rare-metal pegmatites, was not observed in the Kolmozero pegmatites. Columbite-group minerals occur in all main parageneses of the pegmatites and form four generations, reflecting the sequence of pegmatite formation. These minerals demonstrate wide variations in the content of major and trace elements. The composition of CGM ranges from columbite-(Fe) to tantalite-(Mn). Fractionation trends were observed in Mn/(Mn + Fe) versus Ta/(Ta + Nb) diagrams and trace-element abundances plotted versus XTa and XMn. The early CGM paragenesis is characterized by homogeneous, oscillatory and progressive oscillatory zoning and corresponds to a primary magmatic type. Late-generation CGM show patchy irregular internal textures replacing earlier regular patterns of zoning. The irregular zoning points to metasomatic replacement processes. For the first time, it is shown that distributions of rare earth elements (REE) in CGM reflect the evolution of a pegmatite-forming system. At Kolmozero, the main trend of REE variation from early to late generations of CGM involves decreasing total REE contents due to a decrease in heavy REE and Y, decreasing negative Eu anomaly and decreasing magnitude of M-shape tetrad effect between Gd and Ho. These changes are accompanied by gradual flattening of the “bird-like” patterns of chondrite-normalized REE distribution. All these features are typical for late differentiates of granitic volatile-rich magma. Late metasomatic tantalite-(Mn) is characterized by sharp changes in its REE distribution pattern: decreasing total REE contents, changing shape of the REE distribution pattern, the absence of Eu anomaly and tetrad effects, and the appearance of a negative Ce anomaly. The textural characteristics and mineral chemistry of CGM indicate that the pegmatite-forming system underwent several stages of evolution. The earliest magmatic stage can be divided into two sub-stages, involving direct crystallization and collective recrystallization, respectively, and was succeeded by a late hydrothermal–metasomatic post-magmatic stage. Variations in chemical composition among the different generations of CGM are explained by the interplay of several processes: fractional crystallization; competitive crystallization of main rock-forming (feldspar, muscovite, spodumene) and accessory (triphylyte–lithiophilite, spessartine, fluorapatite, zircon, microlite) minerals; and evolution of the mineral-forming environment from a melt to a hydrothermal–metasomatic fluid.     

Lahnsteinite, Zn4(SO4)(OH)6 · 3H2O, a new mineral from the Friedrichssegen Mine, Germany

A new mineral, lahnsteinite, has been found in the dump of the Friedrichssegen Mine, Bad Ems district, Rhineland-Palatinate (Rheinland-Pfalz), Germany. Lahnsteinite, occurring as colorless tabular crystals in the cavities of goethite, is associated with pyromorphite, hydrozincite, quartz, and native copper. The Mohs’ hardness is 1.5; the cleavage is perfect parallel to (001). D _calc = 2.995 g/cm³, D _meas = 2.98(2) g/cm³. The IR spectrum is given. The new mineral is optically biaxial, negative, α = 1.568(2), β = 1.612(2), γ = 1.613(2), 2V _meas = 18(3)°, 2V _calc = 17°. The chemical composition (wt %, electron microprobe data; H₂O was determined by gas chromatography of ignition products) is as follows: 3.87 FeO, 1.68 CuO, 57.85 ZnO, 15.83 SO₃, 22.3 H₂O, total is 101.53. The empirical formula is (Zn_3.3Fe_0.27Cu_0.11)_Σ3.91(S_0.98O₄)(OH)₅ · 3H_2.10O. The crystal structure has been studied on a single crystal. Lahnsteinite is triclinic, space group P1, a = 8.3125(6), b = 14.545(1), c = 18.504(2) Å, α = 89.71(1), β = 90.05(1), γ = 90.13(1)°, V = 2237.2(3) ų, Z = 8. The strong reflections in the X-ray powder diffraction pattern [d, Å (I, %)] are: 9.30 (100), 4.175 (18), 3.476 (19), 3.290 (19), 2.723 (57), 2.624 (36), 2.503 (35), 1.574 (23). The mineral has been named after its type locality near the town of Lahnstein. The type specimen of lahnsteinite is deposited in the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, registration number 4252/1.     

Ferrovalleriite, 2(Fe,Cu)S · 1.5Fe(OH)2: Validation as a mineral species and new data

Ferrovalleriite, ideally 2(Fe,Cu)S · 1.5Fe(OH)₂, a layered hydroxide-sulfide of the valleriite group and an analog of valleriite with Fe instead of Mg in the hydroxide block, has been approved by the IMA Commission on New Minerals, Nomenclature and Classification as a valid mineral species. It was found in the Oktyabr’sky Mine, Noril’sk, Krasnoyarsk krai, Siberia, Russia. Ferrovalleriite occurs in cavities of massive sulfide ore mainly consisting of cubanite and mooihoekite. In different cases, it is associated with magnetite, Fe-rich chlorite-like phyllosilicate, ferrotochilinite, hibbingite, or rhodochrosite. Ferrovalleriite forms crystals flattened on [001] (from scaly to tabular; up to 5 mm across and up to 0.3 mm thick), typically split and curved. Occasionally, they are combined into aggregates up to 1.5 × 2 cm. Ferrovalleriite is dark bronze-colored, with a metallic luster and black streak. The Mohs’ hardness is ca. 1; VHN is 35 kg/mm². Cleavage is perfect parallel to {001}, mica-like. Individuals are flexible and inelastic. D(calc) = 3.72 g/cm³. In reflected light, ferrovalleriite is pleochroic from yellowish to gray; bireflectance is moderate. Anisotropy is strong, with bluish gray to yellowish beige rotation colors. Reflectance values [R ₁–R ₂ %, (λ, nm)] are: 15.6–16.6 (470), 14.8–20.5 (546), 14.7–22.3 (589), 14.5–24.1 (650). The IR spectrum shows the presence of (OH) groups bonded with Fe cations and the absence of H2O molecules. The chemical composition of the holotype (wt %; electron microprobe, H content is calculated) is as follows: 0.10 Al, 0.03 Mn, 45.31 Fe, 0.07 Ni, 18.29 Cu, 20.37 S, 15.62 O, 0.98 H, total is 100.77. The empirical formula calculated on the basis of 2 S atoms is: Al_0.01Fe_2.55Cu_0.91S₂(OH)_3.07 = (Fe_1.09Cu_0.91)_Σ2S₂ · (Fe _1.34 ²⁺ Fe _0.12 ³⁺ Al_0.01)_Σ1.47(OH)_3.07. The structure of ferrovalleriite is incommensurate (misfit); two sublattices are present: (1) sulfide sublattice, space group $R\bar 3m$ , R3m or R32; the unit-cell dimensions are: a = 3.792(2), c = 34.06(3) Å, V = 424(1) ų and (2) hydroxide sublattice, space group $P\bar 3m1$ , P3m1 or P321; the unit-cell dimensions: a = 3.202(3), c = 11.35(2)Å, V = 100.8(3) ų. Together with this main polytype modification with three-layer (R-cell, Z = 3) sulfide block, the holotype ferrovalleriite contains the modification with one-layer (P-cell, Z = 1) sulfide block (sulfide sublattice with $P\bar 3m1$ , P3m1 or P321, unit cell dimensions: a = 3.789(4), c = 11.35(1) Å, V = 141(5) ų). The strongest reflections in the X-ray powder pattern (d, Å-I) are: 5.69–100; 3.268–58; 3.163–36; 1.894–34; 1.871–45.     

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.     

Günterblassite, (K,Ca)3 − x Fe[(Si,Al)13O25(OH,O)4] · 7H2O, a new mineral: the first phyllosilicate with triple tetrahedral layer

A new mineral, günterblassite, has been found in the basaltic quarry at Mount Rother Kopf near Gerolstein, Rheinland-Pfalz, Germany as a constituent of the late assemblage of nepheline, leucite, augite, phlogopite, åkermanite, magnetite, perovskite, a lamprophyllite-group mineral, götzenite, chabazite-K, chabazite-Ca, phillipsite-K, and calcite. Günterblassite occurs as colorless lamellar crystals up to 0.2 × 1 × 1.5 mm in size and their clusters. The mineral is brittle, with perfect cleavage parallel to (001) and less perfect cleavage parallel to (100) and (010). The Mohs hardness is 4. The calculated and measured density is 2.17 and 2.18(1) g/cm³, respectively. The IR spectrum is given. The new mineral is optically biaxial and positive as follows: α = 1.488(2), β = 1.490(2), γ = 1.493(2), 2V _meas = 80(5)°. The chemical composition (electron microprobe, average of seven point analyses, H₂O is determined by gas chromatography, wt %) is as follows: 0.40 Na₂O, 5.18 K₂O, 0.58 MgO, 3.58 CaO, 4.08 BaO, 3.06 FeO, 13.98 Al₂O₃, 52.94 SiO₂, 15.2 H₂O, and the total is 98.99. The empirical formula is Na_0.15K_1.24Ba_0.30Ca_0.72Mg_0.16F _0.48 ²⁺ [Si_9.91Al_3.09O_25.25(OH)_3.75] · 7.29H₂O. The crystal structure has been determined from a single crystal, R = 0.049. Günterblassite is orthorhombic, space group Pnm2₁; the unit-cell dimensions are a = 6.528(1), b = 6.970(1), c = 37.216(5) Å, V = 1693.3(4) ų, Z = 2. Günterblassite is a member of a new structural type; its structure is based on three-layer block [Si₁₃O₂₅(OH,O)₄]. The strong reflections in the X-ray powder diffraction pattern [d Å (I, %) are as follows: 6.532 (100), 6.263 (67), 3.244 (49), 3.062 (91), 2.996 (66), 2.955 (63), and 2.763 (60). The mineral was named in honor of Günter Blass (born in 1943), a well-known amateur mineralogist and specialist in electron microprobe and X-ray diffraction. The type specimen of günterblassite is deposited in the collections of the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, Russia, with the registration number 4107/1.     

Depmeierite Na8[Al6Si6O24](PO4,CO3)1−x · 3H2O (x < 0.5): A new cancrinite-group mineral species from the Lovozero alkaline pluton of the Kola Peninsula

A new mineral depmeierite, the first cancrinite-group member with the species-forming extraframework anion PO ₄ ^3? , has been found at Mt. Karnasurt in the Lovozero alkaline pluton on the Kola Peninsula in Russia. Natrolite and depmeierite are the major components of a hydrothermal peralkaline veinlet 1.5 cm thick, which cross cuts the foyaite-urtite-lujavrite complex. The associated minerals are steenstrupine-(Ce), vuonnemite, epistolite, sodalite, aegirine, serandite, natisite, and vitusite-(Ce). Depmeierite occurs as colorless transparent isometric grains up to 1 cm in size. Its luster is vitreous. The mineral is brittle, and its cleavage (100) is perfect. Its Mohs hardness is 5, and D(meas) = 2.321(1) and D(calc) = 2.313 g/cm³. Depmeierite is optically biaxial positive, ω = 1.493(2), and ? = 1.497(2). The IR spectrum is given. The chemical composition is as follows (wt %, the average of 10 microprobe analyses with the H₂O and CO₂ determined by selective sorption): 23.04 Na₂O, 0.54 K₂O, 0.03 Fe₂O₃, 29.07 Al₂O₃, 36.48 SiO₂, 3.30 P₂O₅, 0.08 SO₃, 0.97 CO₂, and 5.93 H₂O; the total is 99.44. The empirical formula based on (Si,Al)₁₂O₂₄ is (Na₇₅₈K_0.12)_Σ7.70(Si_6.19Al_5.81O₂₄)[(PO₄)_0.47(CO₃)_0.22(OH)_0.02(SO₄)_0.01]_Σ0.72 · 3.345H₂O. The simplified formula is Na₈[Al₆Si₆O₂₄](CO₃)_{1 ? x} · 3H₂O (x < 0.05). Depmeierite is hexagonal with space group P6₃, and the unit-cell dimensions are a = 12.7345(2), c = 5.1798(1), V = 727.46(2) ų, and Z = 1. The strongest reflections of the X-ray powder pattern (d, Å (I, %) [hkl]) are as follows: 6.380(30) [110], 4.695(91) [101], 3.681(37) [300], 3.250(100) [211], 2.758 (33) [400], 2.596(31) [002], and 2.121(24) [330, 302]. The crystal structure was studied using a single crystal, and R _hkl = 0.0362. Depmeierite differs from cancrinite in the development of wide channels containing Na cations, H₂O molecules, prevailing PO ₄ ^3? -anionic groups, and CO ₃ ^2? . The mineral is named in honor of the German crystallographer Wulf Depmeier (born in 1944). The type specimen is deposited at the Fersman Mineralogical Museum of the Russian Academy of Sciences in Moscow. The cancrinite sensu stricto subgroup separated within the cancrinite group comprises six minerals with AB frameworks, the smallest unit cell is (a ≈ 12.55–12.75, c ≈ 5.1–5.4 Å), and the chain […Na…H₂O…]^∞ exists in narrow channels: cancrinite, vishnevite, cancrisilite, hydroxycancrinite, kyanoxalite, and depmeierite. The P-bearing varieties of the cancrinite-group minerals are discussed, as well as the formation conditions of the noncarbonate members of the group related to intrusive alkaline complexes.     

Vladimirivanovite, Na6Ca2[Al6Si6O24](SO4,S3,S2,Cl)2 · H2O, a new mineral of sodalite group

The results of an examination of vladimirivanovite, a new mineral of the sodalite group, found at the Tultui deposit in the Baikal region are discussed. The mineral occurs in the form of outer rims (0.01–3 mm thick) of lazurite, elongated segregations without faced crystals (0.2 to 3–4 mm in size; less frequently, 4 × 12–15 × 20 mm), and rare veinlets (up to 5 mm) hosted in calciphyre and marble. Vladimirivanovite is irregular and patchy dark blue. The mineral is brittle; on average, the microhardness VHN is 522–604, 575 kg/mm²; and the Mohs hardness is 5.0–5.5. The measured and calculated densities are 2.48(3) and 2.436 g/cm³, respectively. Vladimirivanovite is optically biaxial; 2V _meas = 63(±1)°, 2V _calc = 66.2°; the refractive indices are α = 1.502–1.507 (±0.002), N _m = 1.509–1.514 (±0.002), and N _g = 1.512–1.517 (±0.002). The chemical composition is as follows, wt %: 32.59 SiO₂, 27.39 Al₂O₃, 7.66 CaO, 17.74 Na₂O, 11.37 SO₃, 1.94 S, 0.12 Cl, and 1.0 H₂O; total is 99.62. The empirical formula calculated based on (Si + Al) = 12 with sulfide sulfur determined from the charge balance is Na_6.36Ca_1.52(Si_6.03Al_5.97)_Σ12O_23.99(SO₄)_1.58(S₃)_0.17(S₂)_0.08 · Cl_0.04 · 0.62H₂O; the idealized formula is Na₆Ca₂[Al₆Si₆O₂₄](SO₄,S₃,S₂,Cl)₂ · H₂O. The new mineral is orthorhombic, space group Pnaa; the unit-cell dimensions are a = 9.066, b = 12.851, c = 38.558 Å, V = 4492 ų, and Z = 6. The strongest reflections in the X-ray powder diffraction pattern (dÅ—I[hkl]) are: 6.61–5[015], 6.43–11[020, 006], 3.71–100[119, 133], 2.623–30[20.12, 240], 2.273–6[04.12], 2.141–14[159, 13.15], 1.783–9[06.12, 04.18], and 1.606–6[080, 00.24]. The crystal structure has been solved with a single crystal. The mineral was named in memoriam of Vladimir Georgievich Ivanov (1947–2002), Russian mineralogist and geochemist. The type material of the mineral is deposited at the Mineralogical Museum of St. Petersburg State University, St. Petersburg, Russia.     

Taipingite-(Ce), (Ce73+, Ca2)Σ9Mg(SiO4)3[SiO3(OH)]4F3, a new mineral from the Taipingzhen REE deposit,North Qinling Orogen,central China

A new cerite group mineral species, taipingite-(Ce), ideally (Ce₇³⁺, Ca₂)_Σ9Mg(SiO₄)₃[SiO₃(OH)]₄F₃, has been found in the Taipingzhen rare earth element (REE) deposit in the North Qinling Orogen (NQO), Central China. It forms subhedral grains (up to approximately 100 ​μm ​× ​200 ​μm) commonly intergrown with the REE mineral assemblages and is closely associated with allanite-(Ce), gatelite-(Ce), törnebohmite-(Ce), fluocerite-(Ce), fluocerite-(La), fluorite, bastnäsite-(Ce), parisite-(Ce) and calcite. Taipingite-(Ce) is light red to pinkish brown under a binocular microscope and pale brown to colorless in thin section, and it is translucent to transparent with a grayish-white streak and vitreous luster. This mineral is brittle with conchoidal fracture; has a Mohs hardness value of approximately 5½ and exhibits no cleavage twinning or parting. The calculated density is 4.900(5) g/cm³. Optically, taipingite-(Ce) is uniaxial (+), with ω ​= ​1.808(5), ε ​= ​1.812(7), c ​= ​ε, and a ​= ​b ​= ​ω. Furthermore, this mineral is insoluble in HCl, HNO₃ and H₂SO₄. Electron microprobe analysis demonstrated that the sample was relatively pure, yielding the empirical formula (with calculated H₂O): (Ce_4.02La_1.64Nd_1.49Pr_0.41Sm_0.10Gd_0.02Ho_0.02Tm_0.01Lu_0.02Y_0.03Ca_0.66Mg_0.05Th_0.01–0.51)_Σ9(Mg_0.75Fe_0.25³⁺)_Σ1(SiO₄)₃{[SiO₃(OH)]_3.98[PO₃(OH)]_0.02}_Σ4(F_1.81OH_1.17Cl_0.02)_Σ3. Taipingite-(Ce) is trigonal and exhibits space group symmetry R3c with unit cell parameters a ​= ​10.7246(3) Å, c ​= ​37.9528(14) Å, V ​= ​3780.39(20) ų and Z ​= ​6. The strongest eight lines in the X-ray diffraction pattern are [d in Å(I)(hkl)]: 4.518(50)(202), 3.455(95)(122), 3.297(85)(214), 3.098(35)(300), 2.941(100)(02,10), 2.683(65)(220), 1.945(40)(238) and 1.754(40)(30,18). The crystal structure has been refined to a R₁ factor of 0.025, calculated for the 2312 unique observed reflections (Fo ​≥ ​4σ). The mineral is named after its discovery locality and is characterized as the F-dominant analogue of cerite-(Ce).     

Aklimaite, Ca4[Si2O5(OH)2](OH)4 · 5H2O, a new natural hydrosilicate from Mount Lakargi, the Northern Caucasus, Russia

A new mineral aklimaite, Ca₄[Si₂O₅(OH)₂](OH)₄ · 5H₂O, has been found near Mount Lakargi, Upper Chegem caldera, Kabardino-Balkaria, the Northern Caucasus, Russia, in the skarnified limestone xenolith in ignimbrite. This hydrothermal mineral occurs in a cavity of altered larnite skarn and is associated with larnite, calcium humite-group members, hydrogarnets, bultfonteinite, afwillite, and ettringite. Aklimaite forms transparent, colorless (or occasionally with pinkish tint) columnar or lath-shaped crystals up 3 × 0.1 × 0.01 mm in size, flattened on {001} and elongated along {010}; they are combined in spherulites. The luster is vitreous; the cleavage parallel to the {001} is perfect. D _calc = 2.274 g/cm³. The Mohs’ hardness is 3–4. Aklimaite is optically biaxial, negative, 2V _meas > 70°, 2V _calc = 78°, α = 1.548(2), β = 1.551(3), γ = 1.553(2). The IR and Raman spectra are given. The chemical composition (wt %, electron microprobe) is as follows: 0.06 Na₂O, 0.02 K₂O, 45.39 CaO, 0.01 MnO, 0.02 FeO, 24.23 SiO₂, 0.04 SO₃, 3.22 F, 27.40 H₂O_(calc.), ?1.36 -O=F₂; the total is 99.03. The empirical formula calculated on the basis of 2Si apfu with O + OH + F = 16 is as follows: (Ca_4.02Na_0.01)_Σ4.03[Si_2.00O_5.07(OH)_1.93][(OH)_3.16F_0.84] _Σ4.00 · 5H₂O. The mineral is monoclinic, space group C2/m, a = 16.907(5), b = 3.6528(8), c = 13.068(4) Å, β = 117.25(4)·, V= 717.5(4) ų, Z = 2. Aklimaite is representative of the new structural type, the sorosilicate with disilicate groups [Si₂O₅(OH)₂]. The strongest reflections in the X-ray powder patterns [d, Å (hkl)] are: 11.64(100)(001), 2.948(32)(310, 203), 3.073(20) ( $\bar 404$ , $\bar 311$ ), 2.320(12)(005, 510), 2.901 (11)(004), 8.30(10) $\left( {\bar 201} \right)$ . The type specimen is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow.