Platy Crystals Research Articles

On the synthesis and structure of the copper-molybdenum oxide bronzes: Monoclinic Cu2Mo10O30 and orthorhombic CuMo9O26

Cu2Mo10O30 was prepared as a monophasic material comprising dark blue platy crystals by reacting Cu with MoO3 under argon at 550 ​°C. Single-crystal X-ray diffractometry showed that Cu2Mo10O30 is a stoichiometric compound that crystallizes with a monoclinic (C2/c) cell: a ​= ​16.6359(6); b ​= ​9.3112(3); c ​= ​27.1597(9) Å; β ​= ​102.621(3)° (Z ​= ​8). Electron paramagnetic resonance spectroscopy revealed that Cu2Mo10O30 displays mixed-valency; (CuI2−xCuIIx)(MoV2+xMoVI8−x)O30 (0 ​≪ ​x ​≤ ​2). Differential scanning calorimetry and in situ high-temperature powder X-ray diffractometry showed that Cu2Mo10O30 decomposes ≳550 ​°C under an inert atmosphere. Dark blue acicular crystals of CuMo9O26 were discovered as a side-product in materials prepared inside evacuated glass ampoules at 500 ​°C. Single-crystal X-ray diffractometry showed these to crystallize with an orthorhombic (Pmmn) cell: a ​= ​3.74190(10); b ​= ​26.4941(4); c ​= ​9.15300(10) Å; (Z ​= ​2). Rietveld refinement of the powder X-ray diffraction data for these materials revealed Cu2Mo10O30 with minor CuMo9O26 and ‘Cu0.1MoO3’.

Assessment of impact breakage of carbamazepine dihydrate due to aerodynamic dispersion.

Acicular crystals are very common in pharmaceutical manufacturing. They are very prone to breakage, causing unwanted particle size degradation and problems such as segregation and lump formation. We investigate the breakage pattern of carbamazepine dihydrate, an acicular and platy crystal with cleavage planes. It readily undergoes attrition during isolation and drying stage, causing processing difficulties. We use the aerodynamic dispersion of a very small quantity of powder sample to induce breakage by applying a pulse of pressurised air. The dispersion unit of Morphologi G3 is used for this purpose. The broken particles settle in a chamber and are subsequently analysed using the built-in image analysis software. The shift in the particle size and shape distributions is quantified through which the extent of breakage is determined as a function of the dispersion pressure. The analysis reveals a change of breakage mechanism as the dispersion pressure is increased from primarily snapping along the crystal length to one in which chipping has also a notable contribution. The breakage data are analysed using a modified impact-based breakage model and the breakability index of the carbamazepine dihydrate is determined for the two breakage regimes. The method provides a quick and easy testing of particle breakability, a useful tool for assessing attrition in process plant and grindability in milling operations.

Solid solutions in micas hydrothermally synthesized from kaolinite at 400 °C

A study of mineral assemblages obtained experimentally from kaolinite was carried out by X-ray diffraction and transmission/analytical electron microscopy in the systems K2O-MgO-Al2O3-SiO2-H2O-HCl, Na2O-MgO-Al2O3-SiO2-H2O-HCl, and Na2O-K2O-MgO-Al2O3-SiO2-H2O-HCl at 400 °C and 260 bars. Three sets of reactions with different Mg2+ concentrations and variable Na/K ratios were studied, at increasing run times. All the experiments yielded the assemblage mica + Al-serpentine ± Mg-kaolinite. Transitional kaolinite appears as large platy particles with homogeneous compositions (mean Mg content = 0.42 atoms per formula unit). Serpentine crystals, frequently curved, show an Al-rich composition. Micas form thin platy crystals with variable compositions in the three chemical systems. In the Na-free system, the reactions yielded white mica with high Fe + Mg contents and biotite. In the K-free system, Na-dioctahedral and Na-di,trioctahedral mica formed. The Na + K-bearing system yielded a two-mica assemblages consisting of phengite + di,trioctahedral mica, both with variable Na/K ratios, although with K as the main cation in interlayer positions in di,trioctahedral micas.

Bavsiite, Ba2V2O2[Si4O12], mineral data and crystal structure

AbstractBavsiite from the type locality Gun Claim, Yukon Territory, Canada, occurs as millimetre-sized sky-blue platy crystals in a barium-rich low-temperature skarn related to a porphyritic quartz monzonite stock. Associated minerals are alstonite, baryte, celsian, diopside, fresnoite, mica, suzukiite, walstromite, witherite and minerals of the cerchiaraite group. Bavsiite is optical uniaxial (+), with ω = 1.725(3) and ε = 1.750(3) (589 nm) and pleochroic. Electron microprobe analyses yielded the empirical formula Na0.02Ba1.98Ti0.16Fe2+0.03V4+1.80 Al0.05Si4.00O14 based on 14 oxygen atoms, the simplified chemical formula is Ba2V2Si4O14. Bavsiite is tetragonal, space group I4/m, a = 7.043(1), c = 11.444(2) Å and Z = 2 obtained from single crystal data at 100 K, which are in good agreement with cell parameters from powder diffraction data at 293 K: a = 7.051(1) Å and c = 11.470(1) Å. The eight strongest lines of the powder X-ray diffraction pattern are [d, Å (I,%)(hkl)]: 3.76(30)(112), 3.36(44)(013), 3.004(100)(022), 2.493(43)(220), 2.486(67)(114), 2.286(24)(222), 1.785(39)(116) and 1.763(25)(040). The crystal structure was refined to R = 0.0159 based upon 312 unique reflections with I > 2σ(I). The crystal structure of bavsiite comprises unbranched single [Si4O12]8– rings connected by [VO5]6– square pyramids and BaO12 polyhedra. It can also be considered as cage–like [Si4V2O18]12– clusters built by four SiO4 tetrahedra and two VO5 square pyramids. These clusters are cross–linked to form a pseudo-two-dimensional network (2D) parallel to (001) containing empty channels along the a axis and the 2D networks held together by Ba2+ ions located in channels parallel to the c axis. The structural formula is Ba2V2O2[Si4O12]. Bavsiite is polymorphic to suzukiite, BaVSi2O7, which is orthorhombic.

Straight, bendable and bent organic crystals.

trans-4-Phenylazobenzoic acid (pab) crystallized in three different morphologies: long rod-like crystals, bendable long thin crystals, and bent crystals. Of them, the bent crystals were obtained by recrystallizing after subjecting pab to UV-irradiation in solution. A small amount of cis-form in the bent crystals is responsible for the bent nature, while the elastic bending of thin platy crystals can be understood from the crystal packing.

Mineralogical, crystal morphological, and isotopic characteristics of smooth slope travertine deposits at Reshuitang, Tengchong, China

Reshuitang is an important active hydrothermal area in the Tengchong geothermal field and is characterized by many hot springs and their associated deposits. Detailed mineralogical, crystal morphological, and stable isotopic investigations of the smooth slope fossil travertines at Reshuitang and hydrochemical studies of two active springs around the fossil travertines were conducted to study their genesis. The results show that 1) the modern springs discharge waters with high temperature (>70 °C), near-neutral pH (6.3–8.34), and high saturation indices of calcite and aragonite; 2) the fossil travertines contain calcite and small amounts of Mn-Fe oxides, halite, thenardite, and non‑carbonate debris; 3) the calcite include ray crystals, dendrite crystals, platy crystals, and spike crystals; and 4) δ13C and δ18O of the fossil travertines at Reshuitang range from −1.59‰ to −0.87‰ and 6.48‰ to 7.80‰, respectively. According to comparison between the travertines at Reshuitang and other travertines in Tengchong, all these travertines are thermogene travertines, with a large contribution of mantle degassing to their parent CO2, but are formed at different temperatures. The fossil travertines at Reshuitang, similar to those at Shuzhishi, are formed at high temperatures (near 100 °C), which results in weak microbial activities during the formation of the fossil travertines. Most of the calcite crystals at Reshuitang were non-equilibrium products precipitated directly from the spring waters during the deposition process, while the spike crystals originated from diagenetic dissolution of large calcite crystals. Comparison between the fossil travertines at Reshuitang and other smooth slope travertines from other areas shows these smooth slope travertines have different lithofacies and fabrics. In smooth slope environments, temperature may control the distribution and development of microbes and the intensity of CO2 degassing, and consequently cause the precipitation of contrasting fabrics and lithofacies.

Textural evolution during high-pressure dehydration of serpentinite to peridotite and its relation to stress orientations and kinematics of subducting slabs: Insights from the Almirez ultramafic massif

The Almirez ultramafic massif (SE Spain) preserves the transformation of high-P antigorite (Atg-) serpentinite to chlorite (Chl-) harzburgite (1.6–1.9 GPa; 680–710 °C), a metamorphic reaction that is the primary source of water at the intermediate depth of subducting slabs. We present a detailed μ-CT and EBSD study of oriented samples across the Atg-serpentinite dehydration isograd to investigate the textural evolution during serpentinite dehydration to peridotite and its relation to stress orientations and the kinematics of subducting slabs.Above the Atg-out isograd, Atg-serpentinite shows a prograde mylonitic foliation and a weak Shape Preferred Orientation (SPO) of oxide aggregates defining a N—S stretching lineation. The antigorite Crystal Preferred Orientation (CPO) is characterized by [001]Atg perpendicular to the foliation, and the poles to (100)Atg and (010)Atg distributed in a girdle-like symmetry with [100]Atg nearly parallel to the stretching lineation. The antigorite microstructure and CPO are consistent with deformation by dislocation creep, twinning, and dissolution-precipitation creep. These textures record the long-term shear deformation near the slab interface where the main compressive stress, σ1, was at an acute angle to the foliation.Below the Atg-out isograd, Atg-serpentinite dehydrated to unfoliated, coarse-grainedChl-harzburgite with granofels or spinifex textures distributed in alternating decameter-sized lenses. Crystallization of granofels and spinifex Chl-harzburgite records, respectively, a sequence of slow and fast fluid draining events during serpentinite dehydration under the same orientation of the principal stresses that resulted in the shear deformation of the Atg-serpentinite. Both textural types exhibit coarse-grained textures with systematic mineral CPOs and SPOs and microstructures without evidence of major ductile deformation. The texture of the granofels Chl-harzburgite formed by a topotactic dehydration reaction after Atg-serpentinite coupled to compaction leading to an olivine layering subparallel to the Atg-serpentinite foliation. The olivines of granofels Chl-harzburgite are rounded and display a weak CPO that can be accounted for by the topotactic reaction 〈100〉Atg||〈100〉Ol and (001)Atg||(010)Ol after Atg-serpentinite. Similarly, orthopyroxene shows a marked CPO consistent with the topotactic reaction (100)Opx||(001)Atg and [001]Opx||[100]Atg.Spinifex Chl-harzburgite displays systematic mineral SPO and CPO. Spinifex olivines are tabular on (100)Ol and elongated along [001]Ol (c > b >> a), and define a ESE–WNW platelet lineation. The average texture is characterized by [001]Ol,Opx subparallel to a strong ESE–WNW oxide aggregate lineation, and [100]Ol,Opx and [001]Ol,Opx within a plane of similar orientation to the Atg-serpentinite foliation. The SPOs and CPOs of spinifex Chl-harzburgites are composed of up to four orientation populations of tabular olivines, where one population is volumetrically dominant in all samples. Relative to the main orientation population, the CPO of olivine shows clustered distribution of [100]Ol and [010]Ol maxima rotated at systematic angles around [001]Ol. These clustered CPOs and SPOs show a remarkable correlation with the orientation of the principal paleostresses. The preponderant orientation population of tabular olivines lies on the plane of maximum compression (σ2–σ3 plane) and has [010]Ol and its (100)Ol tabular faces nearly perpendicular to the Atg-serpentinite foliation. This population can be accounted for by oriented growth of platy crystals perpendicular to σ1. The other populations lie in the plane perpendicular to the least compressive stress (σ3) and the planes of maximum shear. The driving force and causes for the oriented crystallization of tabular olivine in these planes is uncertain, but their correlation with paleostresses suggests a cause-effect relationship.Spinifex and granofels Chl-harzburgites show a marked ESE–WNW oxide aggregate lineation that differs in orientation from that of Atg-serpentinite and is approximately parallel to the intermediate compressive stress (σ2). These lineations and the platelet lineation of spinifex Chl-harzburgite may be due to along-strike fluid flow below the permeability barrier that constituted the Atg-out dehydration isograd. Our study shows that the kinematics of the slab, paleostresses, and fluid flow exert a dynamic control on the textures of Atg-serpentinite dehydrating to peridotite in subducting slabs.

Variation in thickness of a layered silicate on spherical silica particles affected HPLC chiral chromatographic resolution

Abstract The proposed study aims to prepare clay-coated spherical silica particles to be applied as a column packing material for chiral high performance liquid chromatography (HPLC). These particles were prepared by directly growing a hectorite-like layered silicate on porous and non-porous amorphous silica. The direct crystallization of the layered silicate was performed using the reactions of lithium fluoride, magnesium chloride, and silica in the presence of urea under hydrothermal conditions (373 K for 2 d) and led to a homogeneous coverage on the silica surfaces within a 0.4 μm thickness of the aggregates. The resulting layered silicate involved full ion-exchange reactions with an enantiomeric Δ-tris(1,10-phenanthroline)ruthenium(II). The organically modified particles packed into a stainless steel tube optically resolved a racemic mixture of tris(acetylacetonato)ruthenium(II) in a flow of methanol. The resolution efficiency determined by the retention time and full width at half maximum was influenced by the crystalline size and could be adjusted using different porosities of the initial silica and by varying the quantities of added Li and Mg ions to the starting mixtures. Fine platy crystals and their thin layer aggregates on the porous silica contributed toward the good resolution efficiency and a reduction in the elution volume owing to the rapid diffusion of the racemic mixture into the layered silicate.

Platy Galena from the Viburnum Trend, Southeast Missouri: Character, Mine Distribution, Paragenetic Position, Trace Element Content, Nature of Twinning, and Conditions of Formation

The Viburnum Trend of southeast Missouri is one of the world’s largest producers of lead. The lead occurs as galena, predominantly in two crystallographic forms, octahedrons and cubes. Many studies have shown that octahedral galena is paragentically early, the more abundant of the two crystal forms, and is commonly modified in the cube. Those studies also have shown that the cubic form is paragenetically later, less abundant than the octahedrons, and may exhibit minor octahedral modifications. Viburnum Trend galena crystals that exhibit a platy form have received almost no study. The reason for their lack of study is the rarity of their occurrence. This communication discusses their character, mine distribution, paragenetic position, trace element contents, nature of twinning, and speculated conditions of formation. It also compares their character to similar platy galena occurrences in Germany, Bulgaria, Russia, Mexico, and notes their occurrence at the Pine Point District in the Northwest Territories of Canada and at the Black Cloud mine in Colorado. Flat, platy galena crystals have been recognized to occur in very small amounts in the Magmont, Buick, Fletcher, Brushy Creek, and Sweetwater mines in the Viburnum Trend. In contrast, platy galena has never been observed to occur at the Casteel, West Fork, #27, #28, and #29 mines in the Trend. The platy crystals have formed early in the paragenetic sequence of the ores, prior to and coated by subsequently deposited druzy quartz and cubic galena. Spinel twinning of the octahedron produces flat platy crystals. The platy galena crystals of the Viburnum Trend are very similar in crystal morphology to platy galena crystals interpreted to be spinel twins in the Gonderbach Ag mine in NW Germany, the Dalnegorsk Pb-Zn (skarn deposit) mine in SE Russia, the Madan ore field of skarn Pb-Zn-Ag deposits of southern Bulgaria, and the large Naica skarn Pb mine of northern Mexico. The crystallization of certain crystal forms of galena has been ascribed to the incorporation of elevated contents of trace elements in some lead districts. Analysis of Viburnum platy galena crystals shows that they contain very low levels of trace elements: 3.1 ppm Ag, <2 ppm Bi, <2 ppm Sb, and <2 ppm As. Thus, elevated trace element content is not the cause for the development of Viburnum platy galena. It is speculated that the Viburnum spinel-twinned galena crystals were the result of rapid crystallization from oversaturated hydrothermal ore fluids.

Templating Growth of a Pseudomorphic Lepidocrocite Microshell at the Calcite–Water Interface

The growth of lepidocrocite (γ-FeOOH) has been observed through oxidation of Fe(II) on calcite (CaCO3). Here, we seek to understand the structural relation between lepidocrocite and the calcite substrate and its growth mechanism. The formation of iron oxyhydroxide layers having distinct morphologies was observed during the dissolution of calcite in acidic Fe(II)-rich solutions. A pseudomorphic lepidocrocite shell together with multiple iron oxyhydroxide layers encapsulated within the shell was imaged by optical and transmission X-ray microscopies. The presence of a several-nanometer-thick ordered lepidocrocite film was observed by X-ray reflectivity, with the lepidocrocite (100) plane oriented parallel to the calcite (104) surface. Lath-shaped lepidocrocite aggregates formed during the initial precipitation, which eventually grew into clusters of parallel platy crystals. The formation of a nanometer-thick well-ordered lepidocrocite film on a pristine calcite surface appears critical for the subsequent pse...

Synthesis of zeolite-A using kaolin samples from Darazo, Bauchi state and Ajebo, Ogun state in Nigeria

Kaolin samples from Ajebo and Darazo in Nigeria were characterized and used to produce zeolite-A crystals. The thermal analysis indicates that both samples undergo de-hydroxylation from 450 o C to about 700 o C and are converted to metakaolin with a weight loss of about 11.39 and 10.43% for the Ajebo and Darazo samples respectively. Characteristic OH, Al-OH, Si-OH and Si-O-Al bands were confirmed in both samples with Infra-red spectroscopy studies. The X-ray diffraction patterns clearly show the presence of the characteristic peaks (12.35 and 24.88 o ) of kaolinite with little quartz impurities. X-ray diffraction measurements (2Ɵ peaks at 7–18 o and 21–35 o ) and scanning electron micrographs clearly show that zeolite-A crystals are produced. The microstructures of kaolin, metakaolin and zeolite-A crystals reveal the presence of platy crystals, amorphous spherical aggregates and cubic-shaped crystals with some amorphous gel respectively. The results show that both Ajebo and Darazo kaolin are suitable for zeolite-A synthesis. http://dx.doi.org/10.4314/njt.v37i1.12

Controlled synthesis of hexagonal α-Fe2O3 crystals for ceramic colors by hydrothermal reaction of FeCl3 and NaOH solutions

Abstract The effect of mixing process of FeCl3 and NaOH solution on the formation of platy (hexagonal) α-Fe2O3 was investigated at 160 and 180 °C by the hydrothermal process. The crystal growth of platy α-Fe2O3 was promoted at higher hydrothermal temperature, higher concentration of NaOH solution and by the addition of FeCl3 solution to NaOH solution instead of the reverse addition. Platy crystals of α-Fe2O3 showed dark red wine color while nanophase equiaxed crystals showed yellowish red color. The platy crystals of 3–6 µm in average diameter kept their platy structure after heating at 900 and 1100 °C in air due to their higher thermal stability towards sintering.

Hydroxykenoelsmoreite, the first new mineral from the Republic of Burundi

We report thenewmineralhydroxykenoelsmoreite,whichhas beenapprovedbytheIMAasIMA2016-056.Themineraloccurs at the Masaka gold mine, Burundi, as rosettes up to 150mm across of platy crystals up to 20μm wide but <2μm thick, associated with goethite and galena. Crystals are canary yellow, transparent with a vitreous lustre, and have a pale yellow streak. Hydroxykenoelsmoreite is uniaxial (-) and non-pleochroic. The refractive indices were too high to measure, but the Gladstone-Dale compatibility index predicts n = 2.065. Crystals are brittle with an irregular fracture, but have perfect cleavage on {0 0 1}. TheMohs hardness is ∼3 by analogy with hydrokenoelsmoreite. The mineral is a member of the elsmoreite group of the pyrochlore supergroup, but deviates from the ideal cubic symmetry due mainly to ordering of Fe onto one of two W sites. Its structure is trigonal, space group R3, with unit-cell parameters a = 7.313(2), c = 17.863(7) A, V = 827(1)A3 and Z = 6. The empirical formula (based on 7 (O+OH) per formula unit (pfu)) is: (□PbCa NaKBa)(W Fe Al)(O(OH))(OH). Raman spectroscopy and bond- valence sums showed that molecular HO was absent or nearly so. The calculated density is 5.806 g cm.

Kampelite, Ba3Mg1.5Sc4(PO4)6(OH)3·4H2O, a new very complex Ba-Sc phosphate mineral from the Kovdor phoscorite-carbonatite complex (Kola Peninsula, Russia)

Kampelite, Ba3Mg1.5Sc4(PO4)6(OH)3·4H2O, is a new Ba-Sc phosphate from the Kovdor phoscorite-carbonatite complex (Kola Peninsula, Russia). It is orthorhombic, Pnma, a = 11.256(1), b = 8.512(1), c = 27.707(4) A, V = 2654.6(3) A3 and Z = 4 (from powder diffraction data) or a = 11.2261(9), b = 8.5039(6), c = 27.699(2) A, V = 2644.3(3) A3 (from single-crystal diffraction data). The mineral was found in a void within the calcite-magnetite phoscorite (enriched in hydroxylapatite and Sc-rich baddeleyite) inside the axial zone of the Kovdor phoscorite-carbonatite pipe. Kampelite forms radiated aggregates (up to 1.5 mm in diameter) of platy crystals grown on the surfaces of crystals of quintinite-2H in close association with pyrite, bobierrite and quintinite-3R. Kampelite is colourless, with a pearly lustre and a white streak. The cleavage is perfect on {001}, the fracture is smooth. Mohs hardness is about 1. In transmitted light, the mineral is colourless without pleochroism or dispersion. Kampelite is biaxial + (pseudouniaxial), α ≈ β = 1.607(2), γ = 1.612(2) (589 nm), and 2V calc = 0°. The calculated and measured densities are 3.28 and 3.07(3) g·cm−3, respectively. The mean chemical composition determined by electron microprobe is: MgO 4.79, Al2O3 0.45, P2O5 31.66, K2O 0.34, Sc2O3 16.17, Mn2O3 1.62, Fe2O3 1.38, SrO 3.44, and BaO 29.81 wt%. The H2O content estimated from the crystal-structure refinement is 7.12 wt%, giving a total of 96.51 wt%. The empirical formula calculated on the basis of P = 6 apfu (atoms per formula unit) is (Ba2.62Sr0.45K0.10Ca0.06)Σ3.23Mg1.60Mn0.28(Sc3.15Fe3+ 0.23Al0.12)Σ3.50(PO4)6(OH)2.61·4.01H2O. The simplified formula is Ba3Mg1.5Sc4(PO4)6(OH)3·4H2O. The mineral easily dissolves in 10% cold HCl. The strongest X-ray powder-diffraction lines [listed as d in A (I) (hkl)] are as follows: 15.80(100)(001), 13.86(45)(002), 3.184(18)(223), 3.129(19)(026), 2.756(16)(402), 2.688(24)(1010). The crystal structure of kampelite was refined to R 1 = 0.092 on the basis of 2620 unique observed reflections. It is based upon complex [MgBa2Sc4(PO4)6] layers consisting of the Ba-PO4 zigzag sheet inserted between two Mg-Sc-PO4 sheets. Raman spectrum of kampelite contains characteristic bands of vibrations of the PO4, ScO6 and H2O groups. Kampelite formed as a result of low-temperature hydrothermal alteration of Sc-bearing baddeleyite, which also produces Sc-rich pyrochlore and juonniite. The structural complexity parameters for kameplite are equal to 5.272 bits/atom and 1244.304 bits/cell, which points out that the mineral is structurally very complex, in agreement with its late-stage hydrothermal origin. The mineral is named in honour of Russian mining engineer Felix Borisovich Kampel’ (b. 1935) for his contribution to the development of technologies of mining and processing of complex magnetite-apatite-baddeleyite ores of the Kovdor deposit.

New Mineral Names*,†

This New Mineral Names has entries for 10 new minerals, including bulgakite, dyrnaesite-(La), eleonorite, gatewayite, joanneumite, mendeleevite-(Nd), morrisonite, nolzeite, packratite, vanarsite and a new data on nalivkinite. # Bulgakite* and New Data on Nalivkinite {#article-title-2} A.A. Agakhanov, L.A. Pautov, E. Sokolova, Y.A. Abdu and V.Y. Karpenko (2016) Two astrophyllite-supergroup minerals: bulgakite, a new mineral from the Darai-Pioz alkaline massif, Tajikistan and revision of the crystal structure and chemical formula of nalivkinite. Canadian Mineralogist, 54(1), 33–48. Bulgakite, (IMA 2014-041), ideally ![Formula][1] , is a new astrophyllite-supergroup mineral. It occurs in the moraine of the Darai-Pioz glacier (39°30′N 70°40′E) in the upper Darai-Pioz alkaline massif in the upper reaches of the Darai-Pioz river, in the area of the joint Turkestan, Zeravshan, and Alay Ranges, Tajikistan. The Darai-Pioz massif is a multiphase intrusion and occupies the core of a large synclinal fold of Carboniferous (Pennsylvanian series) slates. Rocks of the massif have been intruded by fine-grained dikes of biotite tourmaline granites and veins of calcite carbonatites and fenites. Bulgakite was found in a naturally tumbled amphibole–quartz–feldspar boulder of spotty texture, as individual crystals and intergrowths in small cavities (up to 0.5 cm) and as intergrowths (up to 1 cm) of platy crystals and aggregates of poorly crystallized grains. Associated minerals are alkali amphibole, quartz, microcline, bafertisite, aegirine, calcybeborosilite-(Y) , thorite, fluorite, and later crystallized brannockite and sogdianite. Bulgakite is brownish orange with a pale brown streak and a vitreous luster. Cleavage is perfect parallel to {001} and moderate parallel to {010}. The indentation hardness of bulgakite is VHN50 = … [1]: /embed/mml-math-1.gif

Bohseite, ideally Ca4Be4Si9O24(OH4, from the Piława Górna quarry, the Góry Sowie Block, SW Poland

AbstractBohseite is an orthorhombic calcium beryllium aluminosilicate with variable Al content and an endmember formula Ca4Be4Si9O24(OH4), that was discovered in the Piława Górna quarry in the eastern part of the Góry Sowie Block, ∼50 km southwest of Wrocław, SW Poland. It occurs in a zoned anatectic pegmatite dyke in close association with microcline, Cs-rich beryl, phenakite, helvite, 'lepidolite', probably bertrandite and unidentified Be-containing mica as alteration products after a primary Be mineral, probably beryl. Bohseite forms fan-like or parallel aggregates (up to 0.7 cm) of white, platy crystals (up to 2 mm long) with characteristic striations. It is white with a white streak, is translucent and has a vitreous lustre; it does not fluoresce under ultraviolet light. The cleavage is perfect on {001} and fair on {010}, and neither parting nor twinning was observed. Bohseite is brittle with a splintery fracture and Mohs hardness is 5–6. The calculated density is 2.719 g cm–3. The indices of refraction are α= 1.579, β = 1.580,γ = 1.597, all ±0.002; 2Vobs = 24(3)°, 2Vcalc = 27°; the optic orientation is as follows: X ^a= 16.1°, Y ^b= 16.1°, Z //cBohseite shows orthorhombic diffraction symmetry, space groupCmcm,a= 23.204(6),b= 4.9442(9),c= 19.418(6) Å,V= 2227.7(4) Å3,Z= 4. The crystal structure was refined to anR1value of 2.17% based on single-crystal data, and the chemical composition was determined by electron-microprobe analysis. Bohseite is isostructural with bavenite. Bohseite was originally approved with an end-member composition of Ca4Be3AlSi9O25(OH)3, but subsequent discovery of compositions with Be &gt; 3.0 apfu led to redefinition of its end-member composition, holotype sample and locality, as reported here. There is extensive solid solution in bavenite–bohseite according to the schemeO(2)OH–+T(4)Si4++T(3)Be2+↔O(2)O2–+T(4)Al3++T(3)Si4+, and a general formula for the bavenite–bohseite minerals may be written as Ca4BexSi9Al4–xO28–x(OH)x, where x ranges from 2–4 apfu: Ca4Be2Si9Al2O26(OH)2(bavenite) to Ca4Be4Si9O24(OH)4(bohseite).

Telluromandarinoite, A New Tellurite Mineral From the El Indio-Tambo Mining Property, Andes Mountains, Chile

Abstract Telluromandarinoite, a tellurite, is a new mineral species from the Wendy open pit, Tambo mine, El Indio-Tambo mining property, Coquimbo Province, Chile. The ideal endmember telluromandarinoite formula is Fe 3+ 2 Te 4+ 3 O 9 ·6H 2 O and it is the Te 4+ analogue of the selenite mineral mandarinoite, Fe 3+ 2 Se 4+ 3 O 9 ·6H 2 O. These deposits are located in rhyolitic and dacitic pyroclastic volcanic rocks of Tertiary age (8–11 Ma) that are strongly hydrothermally altered. The mineralization in the Tambo area is characterized by high-level epithermal veins and breccias located along roughly east–west structures. Hydrothermal breccias consisting of silicified clasts of dacite tuffs cemented by a silica/barite/alunite matrix are common at the occurrence. In fact, all studied specimens containing tellurite mineralization are associated with alunite. Telluromandarinoite is translucent, pale green, with a white streak and vitreous luster. It forms as individual platy crystals, 0.2 mm or less in size, but more commonly as aggregates of platy crystals. The crystals are too small to allow a Mohs hardness determination; they are brittle with an uneven fracture and no observed cleavage or parting. Telluromandarinoite is biaxial positive with α = 1.750(3), β = 1.807(3), and γ = 1.910(5), with a calculated 2 V = 76.9°. The optical orientation is Y = b , c ˆ Z = 10° in obtuse β. No dispersion was noted and no pleochroism was observed. An average of 10 electron microprobe analyses gave SeO 2 22.91, TeO 2 44.30, Fe 2 O 3 26.43, and H 2 O (calc.) 17.59, total 111.23 wt.%. The mineral loses H 2 O in vacuum, so the high totals obtained were expected. The empirical formula (based on 15 O atoms) is Fe 3+ 2.03 (Te 4+ 1.71 Se 4+ 1.27 ) Σ2.98 O 9 ·6H 2 O with Z = 4, and D calc = 3.372 g/cm 3 . Spot analyses gave stoichiometries that range from telluromandarinoite Fe 3+ 2.03 (Te 4+ 2.12 Se 4+ 0.86 ) Σ2.98 O 9 ·6H 2 O to mandarinoite Fe 3+ 2.07 (Se 4+ 1.64 Te 4+ 1.31 ) Σ2.95 O 9 ·6H 2 O. A crystal-structure analysis shows the mineral to be monoclinic, space group P 2 1 / c , with a 16.9356(5), b 7.8955(3), c 10.1675(3) A, β 98.0064(4)°, and V 1346.32(13) A 3 . The strongest lines in the X-ray powder pattern [ d in A,( I ),( hkl )] are: 8.431(44)(200), 7.153(100), 3.5753(41), 3.4631(21), 2.9964(34), 2.8261(19)(412). The crystal structure of telluromandarinoite is similar to that of emmonsite, Fe 3+ 2 Te 4+ 3 O 9 ·2H 2 O.

New data on celestine-rich salts in the Wieliczka salt deposits

Pale brownish celestine-rich salt rocks were found near the Franciuszek Muller gallery, in the chambers of the 3rd level in the Wieliczka Salt Mine. The complex of rock salts subjected to exploration occurred within a large seam approximately 15 m thick. Detailed research revealed that the salt has the form of a block incorporated within the gray salts body and being similar to other blocks of green salts, well known in the upper part of the deposit. A characteristic petrographical feature of the pale brown rock salt owed to the presence of celestine (SrSO 4 ). That strontium mineral was re-examined, using X-ray powder data, and scanning microscope observations, with EDS analysis. The investigated rock salts exhibited a mineral association of halite (main component), anhydrite, celestine, calcite, gypsum, clay materials, iron compounds and a small amount of bitumen. Interrigenous sediments and the insoluble part of salt occurred higher content of strontium that in halite. Celestine crystals were observed in two forms: elongated platy crystals, forming fan-shaped aggregates and granular aggregates, strongly associated with anhydrite. On carbonate and sulphate strontium usually appearing as needle shaped aggregates of celestine. No barium minerals were observed. The development and paragenesis of celestine suggested a post-sedimentary origin of these rocks that ought to be connected with diagenetic processes. An important observation that confirmed that thesis was the transformation of fine crystalline anhydrite into platy crystals, recrystallization and primary accumulation of strontium, as a result of evaporation processes.

Gold and platinum group minerals in placers of the South Urals: Composition, microinclusions of ore minerals and primary sources

Gold and platinum group minerals from the gold placers of the South Urals are studied in order to identify the metal sources. In placers from the Main Uralian fault zone (MUF), the primary gold contains Ag (up to 29wt.%), Cu (up to 2wt.%) and Hg (up to 4wt.%) and its fineness ranges from 538 to 997‰. Tetra-auricupride and cupriferous gold (up to 20wt.% Cu) are common for the Nizhny Karabash placer of the MUF zone. In the eastern part of the South Urals, the placer gold is mainly characterized by high fineness of 900–1000‰ and low Cu contents (max 1.38wt.%). Most of the placer gold grains consist of the primary domains, which are rimmed by secondary high-fineness gold with diffuse and clear boundaries. The secondary gold also develops along the shear dislocations of primary gold. Gold contains microinclusions of geerite, balkanite, chalcopyrite, Se-bearing galena, sphalerite, pyrite, pyrrhotite, arsenopyrite and hematite.Twenty four (including five unnamed) platinum group minerals (PGMs) were found in 28 placers; those from the Kialim and Maly Iremel placers of the Miass placer zone were studied in details. In the Kialim placer, ruthenium is most abundant PGM, which hosts microinclusions of isoferroplatinum, ferroan platinum, laurite, cupriferous gold, a mineral similar in composition to tolovkite, heazlewoodite and unnamed RhSbS phase. The osmium contains microinclusions of erlichmanite and laurite. The iridium grains hosts various sulfides and arsenides of platinum group elements (PGEs). The inclusion-free PGMs form Ru compositional trend in contrast to Os–Ru trend of the Ir-depleted inclusion-hosted PGMs. The isoferroplatinum from the Maly Iremel placer hosts laurite, rhodarsenite, bowieite, a mineral similar in composition to miassite and unnamed sulfide of Pt (Pt1.11S2.00) and antimonide of Pd ((Pd2.41Rh0.43Fe0.17)3.01(Sb0.91Te0.09)1.00). Ruthenium is a host to isoferroplatinum, PGE sulfides and arsenides, and heazlewoodite. Osmium contains microinclusions of ferroan platinum; iridium is a host to a mineral similar in composition to hongshiite. Three types of PGM intergrowths were identified in the Maly Iremel samples: (1) the intergrowths of platy grains of ruthenium with isoferroplatinum and a mineral similar in composition to tulameenite; (2) the open-latticework intergrowths of platy crystals of ruthenium with interstitial aggregates made up of gold, isoferroplatinum and a mineral similar in composition to xingzhongite and (3) the intergrowths of osmium and irarsite and iridarsenite, which are developed along cleavage of the osmium grains. Nickel sulfides associated with some PGMs contain Ru (11.32wt.%) and Rh (2.21wt.%) in millerite and Ir (31.00wt.%), Ru (5.81wt.%) and Rh (2.87wt.%) in vaesite.The primary metal sources were determined on the basis of the mineral assemblages and composition of minerals, taking into account the nearby mineral deposits and directions of rivers. The rodingite-associated gold, gold-bearing massive sulfide and chromite deposits are major sources of gold and PGMs in placers of the Miass placer zone confined to the MUF structure of the South Urals. In the southern part of this structure, gold was mainly originated from orogenic gold–sulfide deposits associated with volcanic/volcaniclastic rocks and listvenite-associated gold deposits. The placer PGMs were derived from the adjacent ultramafic massifs of ophiolitic origin. The distance between the placers and primary deposits varies from 2 to 5km (up to 20km in the extended valley of the Miass River). Usage of ore microinclusions and associated PGMs in study of placer gold is far more advanced than an ordinary consideration of gold composition alone. This approach allowed us to identify the concrete sources for individual placers and to predict some mineralogical findings in already known primary occurrences.

Riotintoite, Al(SO4)(OH)·3H2O, A New Mineral From La Vendida Copper Mine, Antofagasta Region, Chile

The new mineral riotintoite was discovered in the abandoned La Vendida mine, near Sierra Gorda, Antofagasta Region, Atacama desert, Chile. Associated minerals are vendidaite, eriochalcite, Mg-rich aubertite, magnesioaubertite, belloite, alunite, kaolinite, and halloysite. Riotintoite forms colorless platy crystals up to 0.1 × 0.4 × 0.4 mm in size and exhibits the forms {010} (the major form), {001}, {100}, {110}, {01![Graphic][1] }, {1![Graphic][2] 0}, {2![Graphic][3] 0}, {123}, {![Graphic][4] 23}, {![Graphic][5] 31}, and {1![Graphic][6] 1}. Riotintoite is brittle, with Mohs' hardness of 2½. There are three good cleavages: {010}, {001}, and {201}. D meas = 2.13(2) g/cm3, D calc = 2.129 g/cm3. The new mineral is optically biaxial (–), α 1.513(2), β 1.522(2), γ 1.526(2), 2 V (meas.) = 62(1)°, 2 V (calc.) = 67°. The infrared spectrum is given. The chemical composition (electron microprobe, H2O by gas chromatography) is (in wt.%): Al2O3 24.36, SO3 40.69, H2O 34(2), total 99.05. The empirical formula is: Al0.93(SO4)0.99(OH)0.81·3.25H2O. The crystal structure was solved using single-crystal X-ray diffraction data ( R 1 = 0.0398). Riotintoite is triclinic, space group P ![Graphic][7] , a 5.600(2) A, b 7.450(3) A, c 7.671(3) A, α 74.785(7)°, β 86.042(8)°, γ 75.810(7)°, V 299.4(2) A3, Z = 2. The structure is based on isolated clusters which are formed by pairs of edge-shared Al(H2O)3(OH)2O octahedra (AlO6 octahedra link via common OH–OH edge and O belongs to the SO42– anion) and SO4 tetrahedra. The clusters are linked by strong hydrogen bonds between water molecules and non-bridging oxygen atoms of SO4 tetrahedra. The strongest lines of the powder X-ray diffraction pattern [ d , A ( I , %) ( hkl )] are: 6.975 (100) (010), 4.459 (40) (111), 4.391 (72) (101), 3.766 (31) (![Graphic][8] ![Graphic][9] 1), 3.695 (29) (002, 012), 3.491 (24) (021, 020), 2.552 (26) (201, ![Graphic][10] 01, 013). [1]: /embed/inline-graphic-1.gif [2]: /embed/inline-graphic-2.gif [3]: /embed/inline-graphic-3.gif [4]: /embed/inline-graphic-4.gif [5]: /embed/inline-graphic-5.gif [6]: /embed/inline-graphic-6.gif [7]: /embed/inline-graphic-7.gif [8]: /embed/inline-graphic-8.gif [9]: /embed/inline-graphic-9.gif [10]: /embed/inline-graphic-10.gif