Minerały grupy wezuwianu ze skał achtarandytowych (rzeka Wiluj, Jakucja) : szereg wiluit - wezuwian - Si-deficytowy wezuwian ("hydrowezuwian") : geneza rodingitoidów achtarandytowych

Vesuvianite, a rock-forming mineral typical of skarns and rodingites, has been the object of various recent spectroscopic, structural and genetic investigations. This mineral is characterized by a complex composition and by a structure that reflects the conditions of its growth. Establishing the principles by which the vesuvianite group minerals, including wiluite, manganvesuvianite, and fluorvesuvianite, may be classified is likely to lead to the description of a new mineral species. For a long time, it was considered that minerals of the vesuvianite group in the Wiluy deposit (Yakutia, Russia), the type locality of wiluite, grossular and achtarandite (occurring as a pseudomorph after wadalite), were represented solely by wiluite. The results presented here show that minerals of the vesuvianite group that formed at different stages in the evolution of their host rock are characterized by varying compositions and morphologies, and that they are the rock-forming minerals of the achtarandite rocks. The main aims of the present work are two-fold. 1) The investigation of the morphology, crystal chemistry, structure and growth history of the vesuvianite group minerals belonging to the new isomorphic series hydrovesuvianite” (Si-deficient vesuvianite) - vesuvianite and “hydrovesuvianite” - wiluite. 2) The actualization of an earlier genetic model for the formation of achtarandite rocks

57Fe Mossbauer spectroscopy of annealed metamict davidite

This paper reports preliminary results of 57Fe Mössbauer spectroscopy and X-ray diffraction (XRD) studies of metamict davidite samples (La,Ce,Ca,Th)(Y,U,Fe)(Ti,Fe,Mn)20(O,OH)38 after high temperature annealing in an argon atmosphere. The Mössbauer spectra show a gradual decrease of quadrupole splitting and line width values of an Fe3+ doublet with increasing annealing temperature. Rather unexpected feature of these spectra for an Fe2+ doublet is a considerable increase of the line width with progressive crystallinity and a simultaneous decrease of both quadrupole splitting and isomer shift values. Changes of the hyperfine parameters as a function of the annealing temperature appeared as sensitive indicators of the thermal recrystallization process of metamict davidite similar to metamict silicates

Kahlenbergite, a New Potassium β-Alumina Mineral : [abstract]

32nd European Crystallographic Meeting ECM 32, Vienna Austria, 18. – 23. 08. 201

Not Only Garnets…

Garnets have been known to man since time immemorial and are used in a wide variety of applications as well as being prototypes of useful synthetic materials. Our investigations show that in nature, garnets and minerals with a langasite-type structure can be very close in composition. Examples are cubic Ti-rich garnets with the common formula Ca3(Ti4+,Fe3+,Al)2(Si,Fe3+,Al)3O12 and the new trigonal mineral qeltite, Ca3Ti(Fe3+2Si)Si2O14, which occur in paralavas of the pyrometamorphic Hatrurim Complex, Israel. Synthetic compounds of the langasite family are important because of their functional properties, such as unique piezoelectricity, high thermal stability, and low acoustic losses, as well as optical nonlinearity and multiferroicity. Qeltite is the first high-temperature terrestrial mineral with a langasite-type structure, the description of which was a catalyst for the discovery in pyrometamorphic rocks of the Hatrurim Complex of a whole series of new natural phases with langasite-type structure and varied composition (A3BC3D2O14, where A = Ca and Ba; B = Ti, Nb, Sb, and Zr; C = Ti, Al, Fe, and Si; and D = Si). We think that qeltite and other minerals with langasite-type structure may be relatively widely distributed in terrestrial rocks that form under similar conditions to those of Ti-rich garnet but are missed by researchers

Walstromite, BaCa2(Si3O9), from Rankinite Paralava within Gehlenite Hornfels of the Hatrurim Basin, Negev Desert, Israel

Walstromite, BaCa2Si3O9, known only from metamorphic rocks of North America, was found in small veins of unusual rankinite paralava within gehlenite hornfelses of the Hatrurim Complex, Israel. It was detected at two localities—Gurim Anticline and Zuk Tamrur, Hatrurim Basin, Negev Desert. The structure of Israeli walstromite [with P1 space group and cell parameters a = 6.74874(10)Å, b = 9.62922(11) Å, c = 6.69994(12) Å, α = 69.6585(13)°, β = 102.3446(14)°, γ = 96.8782(11)°, Z = 2, V = 398.314(11) Å3) is analogous to the structure of walstromite from type locality—Rush Creek, eastern Fresno County, California, USA. The Raman spectra of all tree minerals exhibit bands related to stretching symmetric vibrations of Si-O-Si at 650–660 cm−1 and Si-O at 960–990 cm−1 in three-membered rings (Si3O9)6−. This new genetic pyrometamorphic type of walstromite forms out of the differentiated melt portions enriched in Ba, V, S, P, U, K, Na, Ti and F, a residuum after crystallization of rock-forming minerals of the paralava (rankinite, gehlenite-åkermanite-alumoåkermanite, schorlomite-andradite series and wollastonite). Walstromite associates with other Ba-minerals, also products of the residual melt crystallization as zadovite, BaCa6[(SiO4)(PO4)](PO4)2F and gurimite, Ba3(VO4)2. The genesis of unusual barium mineralization in rankinite paralava is discussed. Walstromite is isostructural with minerals—margarosanite, BaCa2Si3O9 and breyite, CaCa2(Si3O9), discovered in 2018

Structural investigations on bredigite from the Hatrurim Complex

Bredigite, Сa7Mg(SiO4)4, is an indicator mineral of metasomatic rocks of the sanidinite facies formed at high temperatures (>800 °C) and low pressures (<1–2 kbar). Bredigite samples from ternesite-gazeevite-larnite pyrometamorphic rocks of the Hatrurim Complex (Negev Desert, Israel) have been studied by electron probe micro analysis and single-crystal diffraction using synchrotron radiation. They are characterized by a relatively uniform composition. The empirical formula calculated on the basis of 16 O atoms per formula unit is: (Ca7.006Na0.015Ba0.014)Σ7.035Mg0.938(Si4.000P0.014)Σ4.014O16. Basic crystallographic data of a sample studied by X-ray diffraction are as follows: orthorhombic symmetry, space group Pnnm, a = 18.38102(17) Å, b = 6.74936(7) Å, c = 10.90328(11) Å, V = 1352.66(2) Å3, Z = 4. Structure solution and subsequent least-squares refinements resulted in a residual of R(|F|) = 0.023 for 2584 independent observed reflections with I > 2σ(I) and 149 parameters. To the best of our knowledge this is the first detailed structural investigation on natural bredigite. In contrast to previous studies on samples retrieved from metallurgical slags there was no need to describe the structure in the acentric space group Pnn2. Furthermore, the problem of Ba incorporation into the bredigite structure is discussed. Data on the composition of Ba-bearing bredigites from pyrometamorphic rocks of the Hatrurim Complex from Jordan with simplified formula Ba0.7Ca13.3Mg2(SiO4)8 (based on 32 oxygen atoms) are provided for the first time, pointing out perspectives of finding new Ba-bearing minerals isostructural with bredigite in nature

Molecular Hydrogen in Natural Mayenite

In the last 15 years, zeolite-like mayenite, Ca12Al14O33, has attracted significant attention in material science for its variety of potential applications and for its simple composition. Hydrogen plays a key role in processes of electride material synthesis from pristine mayenite: {Ca12Al14O32}2+(O2)!{Ca12Al14O32}2+(e)2. Apresence of molecular hydrogen in synthetic mayenite was not confirmed by the direct methods. Spectroscopy investigations of mayenite group mineral fluorkyuygenite, with empirical formula (Ca12.09Na0.03)P 12.12(Al13.67Si0.12Fe3+ 0.07Ti4+ 0.01)P 12.87O31.96 [F2.02Cl0.02(H2O)3.22(H2S)0.15 0.59]P 6.00, show the presence of an unusual band at 4038 cm1, registered for the first time and related to molecular hydrogen, apart from usual bands responding to vibrations of mayenite framework. The band at 4038 cm1 corresponding to stretching vibrations of H2 is at lower frequencies in comparison with positions of analogous bands of gaseous H2 (4156 cm1) and H2 adsorbed at active cation sites of zeolites (4050–4100 cm1). This points out relatively strong linking of molecular hydrogen with the fluorkyuygenite framework. An appearance ofH2 in the fluorkyuyginite with ideal formula Ca12Al14O32[(H2O)4F2], which formed after fluormayenite, Ca12Al14O32[ 4F2], is connected with its genesis. Fluorkyuygenite was detected in gehlenite fragments within brecciaed pyrometamorphic rock (Hatrurim Basin, Negev Desert, Israel), which contains reduced mineral assemblage of the Fe-P-C system (native iron, schreibersite, barringerite, murashkoite, and cohenite). The origin of phosphide-bearing associations is connected with the e ect of highly reduced gases on earlier formed pyrometamorphic rocks

Chlorellestadite, Ca5(SiO4)1.5(SO4)1.5Cl, a new ellestadite- group mineral from the Shadil-Khokh volcano, South Ossetia

Acknowledgements This work was supported by grant no. 2015/17/N/ ST10/03141 (D. Ś.) from the National Science Centre (NCN) of Poland. Professor Pádhraig S. Kennan of University College at Dublin, Ireland, kindly helped with the English language. The authors are grateful to referee Professor S. Mills and Editor-in-Chief Dr. M.A.T.M. Broekmans for their constructive remarks, which greatly improved the original manuscript.Chlorellestadite (IMA2017–013), ideally Ca5(SiO4)1.5(SO4)1.5Cl, the Cl-end member of the ellestadite group was discovered in a calcium-silicate xenolith in rhyodacite lava from the Shadil Khokh volcano, Greater Caucasus, South Ossetia. Chlorellestadite forms white, tinged with blue or green, elongate crystals up to 0.2–0.3 mm in length. Associated minerals include spurrite, larnite, chlormayenite, rondorfite, srebrodolskite, jasmundite and oldhamite. The empirical crystal chemical formula of the holotype specimen is Ca4.99Na0.01(SiO4)1.51(SO4)1.46(PO4)0.03(Cl0.61OH0.21F0.11)Σ0.93. Unit-cell parameters of chlorellestadite are: P63/m, a = 9.6002(2), c = 6.8692(2) Å, V = 548.27(3)Å3, Z = 2. Chlorellestadite has a Mohs hardness of 4–4.5 and a calculated density of 3.091 g/cm3. The cleavage is indistinct, and the mineral shows irregular fracture. The Raman spectrum of chlorellestadite is similar to the spectra of other ellestadite group minerals, with main bands located at 267 cm−1 (Ca–O vibrations), and between 471 and 630 cm−1 (SiO4 4− and SO4 2− bending vibrations) and 850–1150 cm−1 (SiO4 4− and SO4 2− stretching modes). Chlorellestadite forms in xenoliths of calcium-silicate composition when they are exposed to Cl-bearing volcanic exhalations at about 1000 °C under low pressure conditions.NC

Different route of hydroxide incorporation and thermal stability of new type of water clathrate : X-ray single crystal and Raman investigation

Chlormayenite Ca12Al14O32[♦4Cl2] (♦-vacancy) is partially hydrated micro porouss mineral with hydroxide groups situated at various crystallographic sites. There are few mechanisms describing its hydration. The first one assumes Cl- substitution by OH- at the center of the structural cages (W-site). The second one determines the converting a T1O4 tetrahedron to a T1O3(OH)3 octahedron due to the replacement of oxygen at the O2 site by three OH-groups according to the scheme: (O2O2- + W Cl-) → 3 × O2aOH. The third mechanism, not considered so far in the case of zeolite-like minerals, includes the hydroxide incorporation in form of hydrogarnet defect due to the arrangement of tetrahedral (OH)4 in vacant cages. This yields a strong hydrated phase containing even up to 35% of water more than in any currently known mineral applicable to Portland cement. Moreover, water molecules present in different structural cages are stable up to 355 K while dehydroxylation linked to the gradual loss of only 8% of OH- groups according to 3 O2aOH- → O2O2- + W OH- + gH2O occurs at temperature range from 355 K to 598 K

Uvarovite from Reduced Native Fe-Bearing Paralava, Hatrurim Complex, Israel

A new genetic type of chromium garnet—uvarovite with the simplified formula Ca3(Cr,Al,Ti4+,V3+)2(Si,Al)3O12—was detected in unusual wollastonite-gehlenite-bearing paralava within the Hatrurim Complex in Israel. The pyrometamorphic rocks of that Complex usually formed in the sanidinite facies (low pressure and high temperature) and, as a rule, under oxidized conditions. This paralava contains nodules and grain aggregates of native Fe, usually distributed linearly in the rock or located close to gaseous voids. The presence of native iron droplets in association with the “meteoric” phosphide—schreibersite, suggests that the formation of paralava occurred under high-reducing conditions and high temperature, reaching 1500°C. Uvarovite forms xenomorphic grains either randomly distributed within the rock or flattened crystals on the walls of gaseous voids. Analyzed uvarovite indicates a significant enrichment in Ti4+ (up to 8 wt.% TiO2) and V3+ (up to 4.5 wt.% V2O3), the highest concentrations documented for uvarovite. Unlike known uvarovite from different localities, uvarovite from this study does not contain Fe3+, and Fe2+ is present in insignificant amounts. The obtained structural data reveal that the high contribution of hutcheonite, Ca3Ti4+2SiAl2O12 (up to 18%), and goldmanite, Ca3V3+2Si3O12 (up to 11%), end-members increases the lattice parameter a to >12.00 Å. The crystallization of uvarovite occurs in the narrow interval of oxygen fugacity, a little above the iron-wüstite buffer ƒO2 ≥ ΔIW. Uvarovite xenomorphic grains formed due to the decomposition of wollastonite and chromite, including H2S from the intergranular melt/fluid according to the following reaction: Ca3Si3O9 + Fe2+Cr3+2O4 + H2S → Ca3Cr2Si3O12 + FeS + H2O, while the flattened crystals grew from specific melt that formed on the walls of the voids as a result of exposure of hot gas flow. The comparison of the obtained results with available chemical data from previous studies reveals a gap in the natural isomorphic series between andradite and uvarovite