| 1. |
- Ferrow, Embaie, et al.
(författare)
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Characterization of pyrrhotite in Cu-Ni-ore bodies from mines in Botswana by Mossbauer spectroscopy, X-ray diffraction, and thermomagnetometry
- 2006
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Ingår i: European Journal of Mineralogy. - : Schweizerbart. - 1617-4011 .- 0935-1221. ; 18:5, s. 653-664
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Tidskriftsartikel (refereegranskat)abstract
- Cu-Ni ore bodies from five Botswana mines were investigated, using a combination of X-ray diffraction, thermomagnetic measurements, Mossbauer spectroscopy, and Inductively Coupled Plasma-Atomic Absorption Electro-optic Spectroscopy (ICP-AES). The four dominant phases in the ores were found to be pyrrhotite, magnetite, pentlandite, and chalcopyrite. Mossbauer spectroscopy shows that pyrrhotite is the dominant Fe-bearing phase in the samples with 75 % in B-S1, 84 % in B-S2, and 80 % in B-S4 and was selected for detailed characterization. Our results show that the three first techniques provide an excellent approach to estimate the degree of polytype intermixing in pyrrhotite. Accordingly, the ores can be grouped into three types: A hexagonal (or peak-type), with a 5c stacking arrangement; a monoclinic (or Weiss-type), with a 4c stacking arrangement; and a mixture of monoclinic and hexagonal types. A low-temperature study of the monoclinic form shows that the low-temperature magnetic transition close to 35 K has features similar to the Verwey transition in magnetite induced by Jahn-Teller distortion due to orbital order-disorder transition.
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| 2. |
- Ferrow, Embaie
(författare)
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Experimental weathering of biotite, muscovite and vermiculite: a Mossbauer spectroscopy study
- 2002
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Ingår i: European Journal of Mineralogy. - : Schweizerbart. - 1617-4011 .- 0935-1221. ; 14:1, s. 85-95
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Tidskriftsartikel (refereegranskat)abstract
- Biotite, muscovite and vermiculite were treated in HCl and H2SO4 solutions at pH ranging between 7 and 1. The solid residue was studied using Mossbauer spectroscopy at room temperature. The spectra of the untreated samples, D0Bio, D0Mus and DOVer were fitted assuming quadrupole splitting distribution, QSD. Different fitting models with different combinations of Gaussian components for the Fe sites were tested and the models with chi(2) near 1.0+/-0.1237 and with the least number of free parameters were adopted as working models. The models were then used to fit the experimental products of each group. If a model fails to describe a spectrum of a sample in the group then this is taken to signal a significant crystal chemical change induced by weathering. All three minerals are oxidized during weathering and the correlation between oxidation ratio and pH is modeled using a Weibull function. The rate of oxidation in biotite is higher than that in muscovite and vermiculite, The average CS and QS of the Fe sites in a group remain more or less constant during the experiment. However, the position of the peak QS of Fe-[6](2+) in biotite is shifted to low energies with decreasing pH, a measure of the decreasing covalence character of the Fe/Mg-O bonds. In muscovite the major feature observed is the enhancement of the bi-modal distribution of the QSD of Fe-[6](2+) with decreasing pH.
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| 3. |
- Ferrow, Embaie
(författare)
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Non-integral hybrid ions in tourmaline: buffering and geo-thermometry
- 2009
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Ingår i: European Journal of Mineralogy. - : Schweizerbart. - 1617-4011 .- 0935-1221. ; 21:1, s. 241-250
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Tidskriftsartikel (refereegranskat)abstract
- The tourmaline group of minerals is indeed an enigma. Experimental data from optical spectroscopy, electron microscopy, and Mossbauer spectroscopy reveal a host of physical properties that lack a common structural clarification. For example, tourmaline samples change colour when irradiated with X-ray and gamma-ray radiations some reverting back when heated in air; exhibit simultaneous oxidation and reduction on annealing in an atmosphere of H-2; display different plane group symmetries under TEM; possess the most complicated Mossbauer spectra of all Fe-bearing silicates. In this study, four Brazilian samples were chosen for detailed study by Mossbauer spectroscopy to find out a common structural factor to the physical anomalies reported in the literature. It was found out that the tourmaline group of minerals contain multi-valence elements that are involved in electron exchange between the edge-sharing asymmetric Y and Z crystallographic sites. It is conceivable that the host of physical properties recorded in the literature could be due to the inherent structural misfit between the Y and Z sites and the mechanisms adopted to reduce the strain associated along the shared edges. The complexity of non-integral oxidation states possible - due to electron sharing among the different multi-valence elements present in the structure - further enhances the diverse physical properties observed. Moreover, on heating in air, no net oxidation or reduction takes place in the tourmaline group of minerals over a temperature range as long as there are electron donors and acceptors left in the structure, serving simultaneously as potential single-phase buffers and geo-thermometers.
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| 4. |
- Lastusaari, Mika, et al.
(författare)
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The Bologna Stone: history's first persistent luminescent material
- 2012
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Ingår i: European Journal of Mineralogy. - : Schweizerbart. - 1617-4011 .- 0935-1221. ; 24:5, s. 885-890
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Tidskriftsartikel (refereegranskat)abstract
- In 1603, the Italian shoemaker Vincenzo Cascariolo found that a stone (baryte) from the outskirts of Bologna emitted light in the dark without any external excitation source. However, the calcination of the baryte was needed prior to this observation. The stone later named as the Bologna Stone was among the first luminescent materials and the first documented material to show persistent luminescence. The mechanism behind the persistent emission in this material has remained a mystery ever since. In this work, the Bologna Stone (BaS) was prepared from the natural baryte (Bologna, Italy) used by Cascariolo. Its properties, e. g. impurities (dopants) and their valences, luminescence, persistent luminescence and trap structure, were compared to those of the pure BaS materials doped with different (transition) metals (Cu, Ag, Pb) known to yield strong luminescence. The work was carried out by using different methods (XANES, TL, VUV-UV-vis luminescence, TGA-DTA, XPD). A plausible mechanism for the persistent luminescence from the Bologna Stone with Cu+ as the emitting species was constructed based on the results obtained. The puzzle of the Bologna Stone can thus be considered as resolved after some 400 years of studies.
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| 5. |
- Chukanov, Nikita V., et al.
(författare)
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Långbanshyttanite, a new low-temperature arsenate mineral with a novel structure from Långban, Sweden
- 2011
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Ingår i: European journal of mineralogy. - : Schweizerbart. - 0935-1221 .- 1617-4011. ; 23:4, s. 675-681
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Tidskriftsartikel (refereegranskat)abstract
- The new mineral långbanshyttanite was discovered in a specimen from the Långban mine (59.86 degrees N, 14.27 degrees E), Filipstad district, Varmland County, Bergslagen ore province, Sweden. Associated minerals are calcite, Mn-bearing phlogopite, spinels of the jacobsite-magnetite series, antigorite and trigonite. The mineral is named after the old name of the mine, smelter and mining village: Långbanshyttan. Långbanshyttanite is transparent, colourless. It occurs in late-stage fractures or corroded pockets, forming soft, radial and random aggregates (up to 1 mm) of acicular crystals up to 5 x 20 x 400 mu m. D(calc) is 3.951 g/cm(3). The new mineral is biaxial (+), alpha = 1.700(5), beta = 1.741(5), gamma = 1.792(5), 2V (meas.) approximate to 90 degrees, 2V (calc.) = 86 degrees. Dispersion is strong, r < v. The IR spectrum is given. The chemical composition is (electron microprobe, mean of five analyses, wt%): PbO 44.71, MgO 3.79, MnO 13.34, FeO 1.89, P(2)O(5) 0.65, As(2)O(5) 22.90, H(2)O (determined by gas chromatographic analysis of the products of ignition at 1200 degrees C) 14.4; total 101.68. The empirical formula based on 18 O atoms is: Pb(1.97)Mn(1.85)Mg(0.93)Fe(0.26)(AsO(4))(1.96)(PO(4))(0.09)(OH)(3.87)cen ter dot 5.93H(2)O. The simplified formula is: Pb(2)Mn(2)Mg(AsO(4))(2)(OH)(4)center dot 6H(2)O. Single-crystal diffraction data obtained using synchrotron radiation indicate that långbanshyttanite is triclinic, P<(1)over bar>, a = 5.0528(10), b = 5.7671(6), c = 14.617(3) angstrom, alpha = 85.656(14), beta = 82.029(17), gamma = 88.728(13)degrees, V = 420.6(2) angstrom(3), Z = 1, and is a representative of a new structure type. In the structure, edge-sharing MnO(2)(OH)(4) octahedra form zig-zag columns that are linked by isolated AsO(4) tetrahedra. Pb cations having six-fold coordination are located between the AsO(4) tetrahedra. Isolated Mg(H(2)O)(6) octahedra are located in the inter-block space. The strongest lines of the powder diffraction pattern [d, angstrom (I,%) (hkl)] are: 14.48 (100) (001), 7.21 (43) (002), 4.969 (34) (100, 101), 4.798 (28) (003), 3.571 (54) (112, 1-1-1, 01-3, 11-1), 2.857 (45) (020, 021, 114), 2.800 (34) (11-3). Parts of the holotype specimen are deposited in the Fersman Mineralogical Museum of Russian Academy of Sciences, Moscow, Russia, with the registration number 4032/1 and in the collections of the Swedish Museum of Natural History, Stockholm, Sweden, under catalogue number NRM 20100076.
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| 6. |
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| 7. |
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| 8. |
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| 9. |
- Janak, M., et al.
(författare)
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Eclogite-hosting metapelites from the Pohorje Mountains (Eastern Alps): P-T evolution, zircon geochronology and tectonic implications
- 2009
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Ingår i: European Journal of Mineralogy. - : Schweizerbart. - 0935-1221.
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: Phase-equilibrium modelling, geothermobarometry, ion-microprobe dating and mineral chemistry of zircon have been used to constrain the P–T–t evolution of metapelitic kyanite-bearing gneisses from the ultrahigh-pressure (UHP) metamorphic terrane of the Pohorje Mountains in the Eastern Alps. These eclogite-hosting rocks are part of the continental basement of the Austroalpine nappes. Based on calculated phase diagrams in the system Na2O-CaO-K2O-FeO-MgO-MnO-Al2O3-SiO2-H2O (NCKFMMnASH) and conventional geothermobarometry, the garnet-phengite-kyanite-quartz assemblages of gneisses record metamorphic conditions of 2.2–2.7 GPa at 700–800 C. These are considered as minima because of the potential for a diffusion-related modification and reequilibration of the garnet and phengite during early stages of decompression. It is therefore most likely that the gneisses experienced the same peak UHP metamorphism at 3 GPa as associated kyanite eclogites. Decompression and cooling to 0.5 GPa and 550 C led to the consumption of garnet and phengite, and the development of matrix consisting of biotite, plagioclase, K-feldspar sillimanite and staurolite. Textures and phase diagrams suggest a low extent of partial melting during decompression. Cathodoluminescence images as well as zircon chemistry reveal cores encompassed by two types of metamorphic zircon rims. Ion probe U-Pb dating of three zircon cores yielded Permian (286 10, 258 7 Ma) and Triassic (238 7 Ma) concordia ages. The zircon rims are Cretaceous with a mean concordia age of 92.0 0.5 Ma and some cores gave a similar age. The Cretaceous zircons all exhibit very low Th/U ratio (,0.02) typical of metamorphic origin. In these zircons, nearly flat HREE patterns, (Lu/Gd)N ¼ 1–4, and only small negative Eu anomalies indicate formation in the presence of garnet and absence of plagioclase, which is corroborated by occurrence of Mg- and Ca-rich garnet inclusions. Therefore, these zircons are interpreted to record the Cretaceous HP/UHP metamorphism. The 92.0 0.5 Ma age obtained in this study agrees with that (93–91 Ma) determined earlier in the Pohorje eclogites from U/Pb zircon, Sm-Nd and Lu-Hf garnet-whole-rock dating. This implies that the eclogites and their country rocks were subducted and exhumed together as a coherent piece of continental crust. There is no evidence for a me´lange-like assemblage of rocks, which followed different P–T–t paths, or several subduction and exhumation cycles as proposed for some other UHP metamorphic terranes.
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| 10. |
- Ladenberger, Anna, et al.
(författare)
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CO2 fluid inclusions in mantle xenoliths from Lower Silesia (SW Poland) : formation conditions and decompression history
- 2009
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Ingår i: European journal of mineralogy. - : Schweizerbart. - 0935-1221 .- 1617-4011. ; 21:4, s. 751-761
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Tidskriftsartikel (refereegranskat)abstract
- Raman spectroscopy has been applied to determine the density and pressure of formation of CO2 fluid inclusions in mantle xenoliths, carried to the surface at Wilcza Gora in southwestern Poland by early Miocene alkaline magmas. The magmas were generated by partial melting in the transition zone between the spinel and garnet stability fields. Determination of the densities of CO2 inclusions allows calculation of the partial pressures and reconstruction of the depth of xenolith origin as well as their history en route to the surface. The density of CO2 inclusions ranges from 0.06 to 1.10 g/cm(3) in olivines and 0.17 to 1.11 g/cm(3) in orthopyroxenes. Only inclusions with a density above 0.8 g/cm(3) reflect lower crust (ca. 15-30 km) and upper mantle (ca. 30-38 km) conditions. Slight differences in density of the inclusions between olivines and orthopyroxenes can be attributed to their different theological properties during magma ascent. Modelling of pressure and depth within the temperature range in which the xenoliths equilibrated with the magmas yields information about the complex eruption history of basanitic volcanoes. Our estimates are consistent with seismic data that show a regional high-velocity layer at the Moho (ca. 30-35 km deep) with p-wave velocities up to 8 km/s which have been attributed to mafic and ultramafic lithologies.
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| 11. |
- Perdikouri, Christina, et al.
(författare)
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Hydrothermal replacement of Aragonite by Calcite : interplay between replacement, fracturing and growth
- 2013
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Ingår i: European journal of mineralogy. - : Schweizerbart. - 0935-1221 .- 1617-4011. ; 25:2, s. 123-136
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Tidskriftsartikel (refereegranskat)abstract
- The hydrothermal transformation of single aragonite crystals into polycrystalline calcite has been studied under hydrothermal conditions. The transformation involves a fluid-mediated replacement reaction, associated with fracturing of the initial aragonite crystal and growth of calcite throughout various parts of the reacted aragonite. The observed overall preservation of the crystal morphology is typical of an interface-coupled dissolution-reprecipitation mechanism Analysis of the crystallographic orientation of the product calcite using electron backscatter diffraction (EBSD) showed little to no link between the two phases under the studied conditions, with calcite crystallites exhibiting dominantly different crystallographic orientations compared to those of the aragonite and of neighbouring calcite domains. The complexity of the observed textures is mainly a result of the combination of fracturing of the crystal and initiation of nucleation and growth at different points of the exposed aragonite surface. Experiments performed with solutions enriched in O-18 as a tracer for oxygen exchange and monitored by Raman spectroscopy, showed that carbonate ions in the starting solution are mixed with carbonate from the dissolving aragonite, resulting in an O-18 concentration in the product calcite which depended on the local fluid transport through the fractures. As replacement processes among the CaCO3 phases are relevant to a wide range of applications, understanding the mechanisms is essential for the interpretation of observations of natural and/or experimental samples. This study describes the interplay between the replacement process, the fracturing of the crystal and growth of the new phase, calcite, and provides new insights into the mechanism of the aragonite to calcite transition. The combination of the two methods, EBSD and Raman spectroscopy, demonstrates the importance of local fluid composition and transport pathways in determining the isotope and element exchange in mineral replacement reactions.
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| 12. |
- Sundvall, Rickard, 1976-, et al.
(författare)
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Dehydration-hydration mechanisms in synthetic Fe-poor diopside
- 2009
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Ingår i: European journal of mineralogy. - Stuttgart : E. Schweizerbart'sche Verlagsbuchhandlung. - 0935-1221 .- 1617-4011. ; 21:1, s. 17-26
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Tidskriftsartikel (refereegranskat)abstract
- Small amounts (ppm) of OH in nominally anhydrous minerals (NAMs) can have a dramatic effect on the physical properties of the upper mantle. The pyroxenes of the upper mantle have been shown to incorporate substantial numbers of protons forming hydroxyl ions. Enstatite and diopside are the most important endmembers of the pyroxenes in terms of bulk volume in the upper mantle. To further constrain the behavior of hydroxyl ions in clinopyroxene, the dehydration-hydration mechanisms of synthetic 57Fe-doped diopside were investigated. Dehydration was carried out by stepwise heating in air of crystals synthesized at high pressure under water-saturated conditions. FTIR spectra were obtained after each step. Mössbauer spectra were recorded for three of the crystals when there had been a significant decrease in FTIR absorbance intensity. From the Mössbauer spectra we see an increase in the Fe3+ doublet with successive dehydration, although this increase is less than the decrease in OH in terms of atoms per formula unit. This means that the dehydration only partly follows the redox reaction OH− + Fe2+ = O2− + Fe3+ + ½H2, and that additional reactions occur. Hydration experiments were conducted on one crystal in the same manner as the dehydrations, with the exception that hydrogen gas was used during heating. Hydration experiments resulted in re-hydration of the sample to 73 % of the original amount of OH. The calculated Arrhenius equation derived from the diffusion rates during dehydration along [010] yields an activation energy (Ea) of −292 ± 50 kJ mol−1, and D0 = 10±1.9 + 2.3 m2 s−1. The result of the rehydration experiment agrees well with the established diffusion law. Diffusion rates determined for synthetic diopside are almost two orders of magnitude slower than for synthetic enstatite with comparable Fe contents. Compared to natural diopside, diffusion rates in these synthetic samples are slower, probably because of the low iron content. Ea is similar to that of dehydration of pure and low-Fe enstatite.
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| 13. |
- Sundvall, Rickard, 1976-, et al.
(författare)
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Hydrogen diffusion in synthetic Fe-free diopside
- 2009
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Ingår i: European journal of mineralogy. - Stuttgart : E. Schweizerbart'sche Verlagsbuchhandlung. - 0935-1221 .- 1617-4011. ; 21:5, s. 963-970
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen is a widespread trace element in many nominally anhydrous minerals (NAMs) in the Earth's crust and mantle and has profound influence on the physical properties of the host mineral. Of all NAMs from the upper mantle, clinopyroxenes have been shown to contain the highest amount of hydrogen. This study focuses on the dehydration kinetics of pure diopside along [010] and [100]* by thermal annealing under normal atmospheric pressure. The diopside crystals used were synthesized at high pressure under water-saturated conditions. FTIR spectra were obtained after each step, including untreated samples. The Arrhenius equation gives an activation energy (Ea) of -331 ± 50 kJ mol-1 and D0 = 100.9 ± 2.3 m2 s-1 for diffusion along [010]. Diffusion along [100]* gives an Ea-value of -312 ± 55 kJ mol-1 with D0 = 100.5 ± 2.4 m2 s-1. Therefore, our experimental results show no difference between diffusion along [010] and [100]* (within error limits). The diffusion rate in pure synthetic diopside is about one order of magnitude faster than for synthetic diopside with very low Fe contents. A suitable explanation for this behavior is that in the case of low Fe diopside, the rate-limiting process for the protons associated with Fe is probably Fe-diffusion. In contrast, in pure diopside all protons are associated to Mg-defects, which are more mobile than Fe. Nevertheless, compared to natural diopside with appreciable Fe contents, diffusion rates in these synthetic samples are several orders of magnitude slower.
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| 14. |
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| 15. |
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| 16. |
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| 17. |
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| 18. |
- Borghini, Alessia, et al.
(författare)
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Halogen-bearing metasomatizing melt preserved in high-pressure (HP) eclogites of Pfaffenberg, Bohemian Massif
- 2024
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Ingår i: European journal of mineralogy. - : Copernicus Publications. - 0935-1221 .- 1617-4011. ; 36:2, s. 279-300
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Tidskriftsartikel (refereegranskat)abstract
- Primary granitic melt inclusions are trapped in garnets of eclogites in the garnet peridotite body of Pfaffenberg, Granulitgebirge (Bohemian Massif, Germany). These polycrystalline inclusions, based on their nature and composition, can be called nanogranitoids and contain mainly phlogopite/biotite, kumdykolite, quartz/rare cristobalite, a phase with the main Raman peak at 412 cm - 1 , a phase with the main Raman peak at 430 cm - 1 , osumilite and plagioclase. The melt is hydrous, peraluminous and granitic and significantly enriched in large ion lithophile elements (LILE), Th, U, Li, B and Pb. The melt major element composition resembles that of melts produced by the partial melting of metasediments, as also supported by its trace element signature characterized by elements (LILE, Pb, Li and B) typical of the continental crust. These microstructural and geochemical features suggest that the investigated melt originated in the subducted continental crust and interacted with the mantle to produce the Pfaffenberg eclogite. Moreover, in situ analyses and calculations based on partition coefficients between apatite and melt show that the melt was also enriched in Cl and F, pointing toward the presence of a brine during melting.The melt preserved in inclusions can thus be regarded as an example of a metasomatizing agent present at depth and responsible for the interaction between the crust and the mantle. Chemical similarities between this melt and other metasomatizing melts measured in other eclogites from the Granulitgebirge and Erzgebirge, in addition to the overall similar enrichment in trace elements observed in other metasomatized mantle rocks from central Europe, suggest an extended crustal contamination of the mantle beneath the Bohemian Massif during the Variscan orogeny.
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| 19. |
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| 20. |
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| 21. |
- Bosi, Ferdinando, et al.
(författare)
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Oxy-foitite, □(Fe2+Al2)Al6(Si6O18)(BO3)3(OH)3O, a new mineral species of the tourmaline supergroup
- 2017
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Ingår i: European journal of mineralogy. - : Schweizerbart. - 0935-1221 .- 1617-4011. ; 29:5, s. 889-896
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Tidskriftsartikel (refereegranskat)abstract
- Oxy-foitite, □(Fe2+Al2)Al6(Si6O18)(BO3)3(OH)3O, is a new mineral of the tourmaline supergroup. It occurs in high-grade migmatitic gneisses of pelitic composition at the Cooma metamorphic Complex (New South Wales, Australia), in association with muscovite, K-feldspar and quartz. Crystals are black with a vitreous luster, sub-conchoidal fracture and gray streak. Oxy-foitite has a Mohs hardness of ∼7, and has a calculated density of 3.143 g/cm3. In plane-polarized light, oxy-foitite is pleochroic (O= dark brown and E = pale brown), uniaxial negative. Oxy-foitite belongs to the trigonal crystal system, space group R3m, a = 15.9387(3) Å, c = 7.1507(1)Å and V = 1573.20(6)Å3,Z = 3. The crystal structure of oxy-foitite was refined to R1 = 1.48% using 3247 unique reflections from single-crystal X-ray diffraction using MoKα radiation. Crystal-chemical analysis resulted in the empirical structural formula: X(□0.53Na0.45Ca0.01K0.01)Σ1.00Y(Al1.53Fe2+1.16Mg0.22Mn2+0.05Zn0.01Ti4+0.03)Σ3.00Z(Al5.47Fe3+0.14Mg0.39)Σ6.00[(Si5.89Al0.11)Σ6.00O18](BO3)3V(OH)3W[O0.57F0.04(OH)0.39]Σ1.00. Oxy-foitite belongs to the X-site vacant group of the tourmaline-supergroup minerals, and shows chemical relationships with foitite through the substitution YAl3++WO2-→YFe2++W(OH)1–.
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| 22. |
- Cámara, Fernando, 1967-, et al.
(författare)
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Zinkgruvanite, Ba4Mn2+4Fe3+2(Si2O7)2(SO4)2O2(OH)2, a new ericssonite-group mineral from the Zinkgruvan Zn-Pb-Ag-Cu deposit, Askersund, Örebro County, Sweden.
- 2021
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Ingår i: European journal of mineralogy. - : Nicolaus Copernicus University Press. - 0935-1221 .- 1617-4011. ; 33:6, s. 659-673
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Tidskriftsartikel (refereegranskat)abstract
- Zinkgruvanite, ideally Ba4Mn2+4Fe3+2(Si2O7)2(SO4)2O2(OH)2, is a new member of the ericssonite group, found in Ba-rich drill core samples from a sphalerite+galena- and diopside-rich metatuffite succession from the Zinkgruvan mine, Örebro county, Sweden. Zinkgruvanite is associated with massive baryte, barytocalcite, diopside and minor witherite, cerchiaraite-(Al) and sulfide minerals. It occurs as subhedral to euhedral flattened and elongated crystals up to 4 mm. It is almost black, semi-opaque with a dark brown streak. The luster is vitreous to sub-adamantine on crystal faces, resinous on fractures. The mineral is brittle with an uneven fracture. VHN100 = 539 and HMohs ~4½. In thin fragments, it is reddish-black, translucent and optically biaxial (+), 2Vz > 70°. Pleochroism is strong, deep brown-red (E ⊥ {001} cleavage) to olive-pale brown. Chemical point analyses by WDS-EPMA together with iron valencies determined from Mössbauer spectroscopy, yielded the empirical formula (based on 26 O+OH+F+Cl anions): (Ba4.02Na0.03)Σ4.05(Mn1.79Fe2+1.56Fe3+0.42Mg0.14Ca0.10Ni0.01Zn0.01)Σ4.03 (Fe3+1.74Ti0.20Al0.06)Σ2.00Si4(S1.61Si0.32P0.07)Σ1.99O24(OH1.63Cl0.29F0.08)Σ2.00. The mineral is triclinic, space group P–1, with unit-cell parameters a = 5.3982(1) Å, b = 7.0237(1) Å, c = 14.8108(4) Å, α = 98.256(2)º, β = 93.379(2)º, γ = 89.985(2)º and V = 554.75(2) Å3 for Z = 1. The eight strongest X-ray powder diffraction lines are [d Å (I%; hkl)]: 3.508 (70; 103), 2.980(70; 11–4), 2.814 (68; 1–22), 2.777 (70; 121), 2.699 (714; 200), 2.680 (68; 20–1), 2.125 (100; 124, 204), 2.107 (96; –221). The crystal structure (R1 = 0.0379 for 3204 reflections) is an array of TS (titanium silicate) blocks alternating with intermediate blocks. The TS blocks consist of HOH sheets (H = heteropolyhedral, O = octahedral) parallel to (001). In the O sheet, the Mn2+-dominant MO(1,2,3) sites give ideally Mn2+4 pfu. In the H sheet, the Fe3+-dominant MH sites and AP(1) sites give ideally Fe3+2Ba2 pfu. In the intermediate block, SO4 oxyanions and eleven coordinated Ba atoms give ideally 2 × SO4Ba pfu. Zinkgruvanite is related to ericssonite and ferro-ericssonite in having the same topology and type of linkage of layers in the TS block. Zinkgruvanite is also closely compositionally related to yoshimuraite, Ba4Mn4Ti2(Si2O7)2(PO4)2O2(OH)2, via the coupled heterovalent substitution 2 Ti4+ + 2 (PO4)3- →2 Fe3+ + 2 (SO4)2-, but presents a different type of linkage. The new mineral probably formed during a late stage of regional metamorphism of a Ba-enriched, syngenetic protolith, involving locally generated oxidized fluids of high salinity.
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| 23. |
- Doubrovinckaia, Natalia
(författare)
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Tin weathering experiment set by nature for 300 years: natural crystals ofthe anthropogenic mineral hydroromarchite from Creussen, Bavaria, Germany
- 2022
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Ingår i: European Journal of Mineralogy. - : Copernicus GmbH. - 0935-1221 .- 1617-4011. ; 34, s. 563-572
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Tidskriftsartikel (refereegranskat)abstract
- Hydroromarchite is a mineral that so far has been found only in afew locations in the world and recognized as a common product of submarinecorrosion of pewter artefacts. Here we report a new locality for this raremineral found at the Saint James Church archaeological site in Creussen,Germany. There it appeared to be a product of weathering of a tin artefact(a tin button) buried in soil of the churchyard for about 300 years. Themineral, found in paragenesis with romarchite and cassiterite, wasidentified using single-crystal X-ray diffraction.
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| 24. |
- Dubrovinskaia, NA, et al.
(författare)
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Direct transition from cristobalite to post-stishovite alpha-PbO2-like silica phase
- 2001
-
Ingår i: EUROPEAN JOURNAL OF MINERALOGY. - : E SCHWEIZERBARTSCHE VERLAGS. - 0935-1221. ; 13:3, s. 479-483
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Tidskriftsartikel (refereegranskat)abstract
- In situ X-ray studies in diamond anvil cells at pressures over 80 GPa were used to determine a stable silica phase at extreme conditions. We demonstrate that so far unidentified phases obtained on compression of alpha -cristobalite and a new dense silica
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| 25. |
- Dubrovinsky, LS, et al.
(författare)
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Stability of beta-iron: A new synchrotron X-ray study of heated iron at high pressure
- 1998
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Ingår i: EUROPEAN JOURNAL OF MINERALOGY. - 0935-1221. ; 10:1, s. 43-47
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Tidskriftsartikel (refereegranskat)abstract
- We have conducted a new study on the stability of the beta-iron phase at high pressure and temperature. With the X-ray study of the electrically heated iron wire at pressures between 35 and 68 GPa, we are able to demonstrate the reversibility of transform
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| 26. |
- Dubrovinsky, L, et al.
(författare)
-
Stability of (Mg0.5Fe0.5)O and (Mg0.8Fe0.2)O magnesiowustites in the lower mantle
- 2001
-
Ingår i: EUROPEAN JOURNAL OF MINERALOGY. - : E SCHWEIZERBARTSCHE VERLAGS. - 0935-1221. ; 13:5, s. 857-861
-
Tidskriftsartikel (refereegranskat)abstract
- We have heated magnesiowtistites (Mg0.5Fe0.5)O and (Mg0.8Fe0.2)O to temperatures of over 1000 K at pressures of over 80 GPa simulating the stability of the solid solution at physical conditions relevant to the Earth's lower mantle. The X-ray study of the
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| 27. |
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| 28. |
- Ferrow, Embaie A., et al.
(författare)
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Crystal chemistry and defect structure of ekmanite : New data from transmission electron microscopy and Mossbauer spectroscopy
- 1999
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Ingår i: European Journal of Mineralogy. - 0935-1221. ; 11:2, s. 299-308
-
Tidskriftsartikel (refereegranskat)abstract
- Ekmanite is a member of the 2:1 type modulated layer silicates such as ganophyllite and bannisterite. Its chemical composition can be represented by K(M20)[Si32O76](OH)16 (M = Fe2+, Mg2+, Mn2+) where three of eight Si-tetrahedra are inverted across the interlayer sharing an apical oxygen with similarly inverted tetrahedra from the adjacent layers. The arrangement of the regular, D, and inverted, R, tetrahedra has the configuration 4D2R1D1R4D... along the b-axis. In local regions of possibly high Mg/(Mn+Fe) ratio, this configuration is interrupted by the absence of inverted tetrahedra. Ekmanite typically contains a multitude of defects; twinning and both regular and irregular stacking arrangements are the most common ones. Ekmanite is sensitive to oxidation and an unidentified phase, chemically related to it, is always found lining its grain boundaries. This texture results in intergrown rods defining polygons where the central parts do not contain ekmanite. The Mossbauer spectrum consists of Fe2+ and Fe3+ absorption doublets with the Fe2+ absorption composed of two Gaussian line pairs and the Fe3+ absorption of a single but broad line pair.
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| 29. |
- Ferrow, EA, et al.
(författare)
-
Compositional control of plane group symmetry in tourmalines : an experimental and computer simulated TEM, crystallographic image processing and Mossbauer spectroscopy study
- 1993
-
Ingår i: European Journal of Mineralogy. - 0935-1221. ; 5:3, s. 479-492
-
Tidskriftsartikel (refereegranskat)abstract
- Tourmalines with different compositions show different plane group symmetries in experimental high resolution transmission electron microscopy (HRTEM) when projected along the c-axis. Fe-poor elbaite shows p31m symmetry, while Fe-bearing elbaite shows p3m1 symmetry. Rubellite shows p6 symmetry, while Fe-Mg-Al-bearing tourmaline shows a `pseudo' p6 type of symmetry. Symmetries p3m1 and p6 are not compatible with the space group R3m assigned to tourmaline from X-ray structural determination studies. The perturbations of symmetry from p31m to p6 and `pseudo' p6 depend on the magnitude of the scattering amplitude of the atoms occupying the 3a and 9b sites. Furthermore, computer simulations of elbaite, schorl and dravite show different projected potentials for images down the c-axis. Regions with high mean concentration of light or heavy elements a few unit cells apart are common in Fe-poor elbaite. This results in a marked difference of the distribution contrast in the HRTEM image of elbaite. The Mossbauer effect (ME) spectra of tourmaline are different with different Mossbauer parameters, reflecting the difference in composition. Experimental HRTEM, computer simulation and ME indicate that composition controls symmetry, ME parameters and atomic coordinates in tourmaline, an observation not recorded in other minerals.
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| 30. |
- Gonzalez-Jimenez, José Maria, et al.
(författare)
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Titanian clinohumite and chondrodite in antigorite serpentinites from Central Chile : evidence for deep and cold subduction
- 2017
-
Ingår i: European journal of mineralogy. - : E. Schweizerbart'sche Verlagsbuchhandlung. - 0935-1221 .- 1617-4011. ; 29:6, s. 959-970
-
Tidskriftsartikel (refereegranskat)abstract
- Humite minerals, including Ti-rich, hydroxyl-dominant chondrodite and clinohumite, occur in Paleozoic antigorite serpentinite in the La Cabaña area, in the Chilean Coastal Cordillera (~38° 30 ′ S–73° 15 ′ W). This may be the first report from South America. Humite minerals are intergrown with Mn-rich olivine hosting antigorite blades in textural equilibrium, indicating a metamorphic origin. A comparison with previous results from piston-cylinder experiments and petrological studies of other high-P serpentinites constrains the formation conditions of the humite + olivine + antigorite assemblage to ca. 2.0–2.5 GPa and <600°C. Thus, the assemblage is interpreted as having formed during cold subduction of a segment of oceanic lithosphere to a depth >60 km, suggesting that the Paleozoic serpentinites were entrained into the mantle at higher P– T conditions than those experienced by the spatially associated olivine–lizardite metadunites and enclosing metasedimentary rocks (subducted to < 30 km). During exhumation along the subduction channel, high- P serpentinites together with metadunites underwent tectonic mingling with metasediments of the accretionary prism, preserving their signature of distinct metamorphic trajectories. This could be similar to the tectonic evolution of blueschists and high-P amphibolites found as isolated blocks in the metasediments of the Chilean Coastal Cordillera.
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| 31. |
- Grew, Edward S., et al.
(författare)
-
Fluor-elbaite, lepidolite and Ta–Nb oxides from a pegmatite of the 3000Ma Sinceni Pluton, Swaziland: evidence for lithium–cesium–tantalum (LCT) pegmatites in the Mesoarchean
- 2018
-
Ingår i: European journal of mineralogy. - : Schweizerbart. - 0935-1221 .- 1617-4011. ; 30:2, s. 205-218
-
Tidskriftsartikel (refereegranskat)abstract
- Mineral evolution is concerned with the timing of mineral occurrences, such as the earliest reported occurrences in the geologic record. Minerals containing essential Li have not been reported from rocks older than ca. 3000 Ma, thus the lithian tourmaline (fluor-elbaite) and mica (lepidolite) assemblage from a pegmatite near Zishineni associated with the ca. 3000Ma Sinceni Pluton presents unusual interest. Fluor-elbaite (0.75–0.98 F per formula unit) forms green crystals up to 50mm long. Spindle stage measurements give ω = 1.652(1), ε = 1.627(1) (589.3 nm). Optical absorption spectroscopy shows Fe and Mn are divalent; infra-red spectroscopy demonstrates the presence of Li and indicates the presence of (OH) at both the (OH) sites. Electron microprobe analysis of 330 points on several prisms, the largest of which is zoned in Fe and Ca, gives the following average and standard deviations in wt%: SiO2 37.29 (0.26), TiO2 0.05 (0.05), Al2O3 38.14 (0.35), Cr2O3 0 (0.02), MgO 0.02 (0.01), MnO 3.57 (0.25), FeO 2.48 (0.60), Na2O 2.48 (0.09), K2O 0.03 (0.12), CaO 0.77 (0.21), F 1.80 (0.11), Cl 0 (0.01) wt%. Nuclear reaction analyses gave Li2O 0.91 (0.04) and B2O3 10.55 (0.45). The empirical formula of fluor-elbaite was determined by integrating crystal-chemical data from electron microprobe analysis, nuclear reaction analysis, crystal structure refinement using X-ray diffraction, infra-red and optical absorption spectroscopy:X(□0.09Na0.77K0.01Ca0.13)Σ1.00 Y(□0.35Li0.59Mn2+0.49Fe2+0.33Al1.23Ti0.01)Σ3.00Al6(Si6O18)(BO3)3O3(OH)3O1[F0.92(OH)0.08]Σ1.00. The crystal structure of fluor-elbaite was refined to statistical indices R1 for 1454 reflections ∼2% using MoKa X-ray intensity data. Structural data confirm the presence of significant vacancies at the Y site. Micas include lepidolite in flakes several millimeters across that are veined and overgrown by fine-grainedmuscovite. Silica and (FeO+MnO) increase, and Al decreases with F, all giving tight linear fits for both micas taken together, suggesting bothmicas can be regarded as interstratified muscovite and lithium mica consisting of 35.2 wt% masutomilite containing nearly equal amounts of Mn and Fe, 52.8 wt% polylithionite and 11.9 wt% trilithionite. Muscovite and lepidolite contain <0.2 wt% and 0.7–2.25 wt% Cs2O and 1.0–1.1 wt% and 1.4–1.5wt% Rb2O, respectively. Other minerals include spessartine (e.g., Sps93Alm4Grs3) in scattered grains up to 0.5mm across and monazite.Oxides occur sparsely in muscovite, rarely in lepidolite, as grains up to 11 mm long, including fluorcalciomicrolite, columbite-(Mn) withNb>Ta, hübnerite(?) and a possible Pb-bearing microlite (Ta>Nb). The oxides, together with the muscovite, are interpreted to be related to later hydrothermal reworking of the primary lepidolite–fluorelbaite assemblage. Given the 2990 ± 43MaRb–Sr isochron and 3074 ± 4Ma evaporation Pb–Pb ages reported for the Sinceni Pluton and Rb/Sr mineral ages ranging from 2906 ± 31Ma to 3072 ± 33Ma reported for the pegmatites, the fluor-elbaite–cesian lepidolite–fluorcalciomicrolite-bearing pegmatite is the first reported occurrence of a lithian tourmaline and lepidolite in the geologic record, as well as one of the two earliest known examples of the lithium–cesium–tantalum (LCT) family of pegmatites. The Sinceni magma is most plausibly derived from a metasedimentary source by intrusion of hot mantle melts into the crust from below, thereby indicating that a “mature” continental crust existed in the Kaapvaal craton at ca. 3000 Ma.
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| 32. |
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| 33. |
- Holtstam, Dan, et al.
(författare)
-
Delhuyarite-(Ce) – Ce4Mg(Fe3+2W)□(Si2O7)2O6(OH)2 – a new mineral of the chevkinite group, from the Nya Bastnäs Fe–Cu–REE deposit, Sweden
- 2017
-
Ingår i: European journal of mineralogy. - : Schweizerbart. - 0935-1221 .- 1617-4011. ; 29:5, s. 897-905
-
Tidskriftsartikel (refereegranskat)abstract
- Delhuyarite-(Ce) is a new mineral (IMA no. 2016-091) with ideal formula Ce4Mg(Fe3+2W)□(Si2O7)2O6(OH)2. It is named after Juan and Fausto de Elhuyar (Delhuyar), chemists and metallurgists, who in 1783 isolated tungsten metal for the first time. Associated minerals in the only known sample, from the Nya Bastnäs Fe–Cu–REE deposit (Västmanland, Sweden), include cerite-(Ce), tremolite‒actinolite, percleveite-(Ce), bastnäsite-(Ce), ferriallanite-(Ce), törnebohmite-(Ce), magnetite, chalcopyrite, quartz and scheelite. Delhuyarite-(Ce), which forms subhedral crystals up to 0.3mm long, is brown–black with a dark brown streak and translucent with an adamantine lustre. It is pleochroic in black to rust red and optically biaxial (-). Calculated density and mean refractive index are 5.20 g·cm-3 and 1.94, respectively. Chemical analyses (electron microprobe) gave (in wt%) La2O3 14.58, Ce2O3 23.29, Pr2O3 1.89, Nd2O3 6.13, Sm2O3 0.74, Gd2O3 0.37, Dy2O3 0.03, Er2O3 0.04, Yb2O3 0.12, Y2O3 0.22, CaO 0.76, Fe2O3 12.86, MgO 2.43, Al2O3 0.73, SiO2 18.16, TiO2 0.09, WO3 15.53, H2Ocalc 1.33, F 0.05, Cl 0.03, O=(F, Cl) 0.03, sum 99.35, corresponding to an empirical formula: (Ce1.89La1.19Nd0.48Pr0.15Sm0.06Gd0.03Y0.03Ca0.18)Σ4.01(Fe3+2.14W0.89Mg0.80Al0.19Ti0.02)Σ4.04Si4.01O20(OH1.96F0.04)Σ2, based on 22 O atoms per formula unit (apfu). The presence of H2O is confirmed by IR-spectroscopy, from a strong absorption band at 3495 cm-1. Delhuyarite-(Ce) is monoclinic, space group C2/m, with unit-cell parameters a =13.6020(6)Å, b = 5.7445(3)Å, c = 10.9996(5)Å, β = 100.721(4)°, V = 844.47 (6)Å3 and Z = 2 (data for natural crystal). The crystal structure was refined to an R1 index of 3.9% (natural crystal) and 1.8% (annealed). Delhuyarite-(Ce) has the same structural topology as chevkinite subgroup minerals, e.g. chevkinite-(Ce). It is the only mineral of the group with a significant content of W6+ = 0.89 apfu. In delhuyarite-(Ce), Mg is dominant at the M1 site as in polyakovite-(Ce); the composition of the M2, M3 and M4 sites is [(Fe3+2W)□], with M2 being 50% vacant.
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| 34. |
- Holtstam, Dan, 1963-, et al.
(författare)
-
Ferri-taramite, a new member of the amphibole supergroup, from the Jakobsberg Mn-Fe deposit, Varmland, Sweden
- 2022
-
Ingår i: European Journal of Mineralogy. - : Copernicus GmbH. - 0935-1221 .- 1617-4011. ; 34:5, s. 451-462
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Tidskriftsartikel (refereegranskat)abstract
- Ferri-taramite (IMA CNMNC 2021-046), ideally Na-A(B) (CaNa)(C) (Mg3Fe23+)(Si6Al2)O-22(W) (OH)(2), occurs in skarn from the Jakobsberg manganese mine, Varmland, Sweden. Associated minerals are celsian, phlogopite, aegirine-augite, andradite, hancockite, melanotekite, microcline (var. hyalophane), calcite, baryte, prehnite, macedonite and oxyplumboromeite. Conditions of formation, close to peak metamorphism (at circa 650 degrees C and 0.4 GPa), include silica undersaturation, a slightly peralkaline character and relatively high oxygen fugacities. Ferri-taramite forms poikiloblastic crystals up to 5 mm and is dark brownish black with a yellowish grey streak. The amphibole is brittle with an uneven to splintery fracture. Cleavage parallel to {110} is good. Hardness (Mohs) is similar to 6, and D-calc = 3.227(5) g cm(-3). Holotype ferri-taramite has the experimental unit formula (A)(Na0.79K0.16Pb0.01)(Sigma 0.96)(B) (Ca1.26Na0.72Mn0.022+)(Sigma 2)(C )(Mg2.66Mn0.582+ Fe0.162+Zn0.02Fe1.263+ Al0.26Ti0.06)(Sigma)(T)(5.00) (Al1.86Si6.14)Sigma 8O(22)(W) (OH)(2), based on chemical analyses (EDS, laser-ablation ICP-MS) and spectroscopic (Mossbauer, infrared) and single-crystal X-ray diffraction data. The mineral is optically biaxial (-), with alpha = 1.670(5), beta = 1.680(5) and gamma = 1.685(5) in white light and 2 V-meas = 70(10)degrees and 2 V-calc = 70.2 degrees. Ferri-taramite is distinctly pleochroic in transmitted light, with X pale yellow, Y dark brown, Z yellowish brown and absorption Y> Z> X. The eight strongest reflections in the X-ray powder pattern (d values (in angstrom), I-rel, hkl) are 8.44, 60, 110; 3.392, 25, 131; 3.281, 39, 240; 3.140, 100, 310; 2.816, 45, 330; 2.7104, 38, 151; 1.3654, 26, 461; and 1.4451, 33, (6) over bar 61. Refined unit-cell parameters from single-crystal diffraction data are a = 9.89596(13), b = 18.015(2), c = 5.32164(7) angstrom, beta = 105.003(13)degrees and V = 916.38(2) angstrom(3) for Z = 2. Refinement of the crystal structure yielded R = 2.26 % for 2722 reflections with I-0 >2 sigma (I). The Mn2+ and Fe2+ ions show preference for the M1 and M3 octahedrally coordinated sites, whereas Fe3+ is strongly ordered at M2. The A-group cations, K and Na, are split over two subsites, A (m) and A(2), respectively.
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| 35. |
- Holtstam, Dan, 1963-, et al.
(författare)
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Hjalmarite, a new Na-Mn member of the amphibole supergroup, from Mn skarn in the Långban deposit, Värmland, Sweden.
- 2019
-
Ingår i: European journal of mineralogy. - : Schweizerbart. - 0935-1221 .- 1617-4011. ; 31, s. 565-574
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Tidskriftsartikel (refereegranskat)abstract
- Hjalmarite, ideally ANaB(NaMn)CMg5TSi8O22W(OH)2, is a new root-name member of the amphibole supergroup, discovered in skarn from the Långban Fe-Mn-(Ba-As-Pb-Sb-Be-B) deposit, Filipstad, Värmland, Sweden (IMA-CNMNC 2017-070). It occurs closely associated with mainly rhodonite and quartz. It is grayish white with vitreous luster and non-fluorescent. The crystals are up to 5 mm in length and display splintery fracture and perfect cleavage along {110}. Hjalmarite is colorless (non-pleochroic) in thin section and optically biaxial (-), with α = 1.620(5), β = 1.630(5), γ = 1.640(5). The calculated density is 3.12 Mg/m3. Average VHN100 is 782, corresponding to circa 5½ Mohs. An empirical formula, derived from EPMA analyses in combination with crystal structure refinements, is (Na0.84K0.16)Σ1(Na1.01Mn0.55Ca0.43Sr0.01) Σ2(Mg3.83Mn1.16Al0.01) Σ5(Si7.99Al0.01) Σ8O22(OH1.92F0.08)Σ2. An infra-red spectrum of hjalmarite shows distinct absorption bands at 3673 cm-1 and 3731 cm-1 polarized in the α direction. The eight strongest Bragg peaks in the powder X-ray diffraction pattern are [d (Å), I (%), (hkl)]: 3.164, 100, (310); 2.837, 50, (330); 8.50, 44, (110); 3.302; 40, (240); 1.670, 34, (461); 1.448, 32, (-661); 2.727, 30, (151); 2.183, 18 (261).Single-crystal X-ray diffraction data were collected at 298 K and 180 K. The crystal structure was refined in space group C2/m to R1=2.6% [I>2(I)], with observed unit-cell parameters a = 9.9113(3), b = 18.1361(4), c = 5.2831(5) Å, β=103.658(5)° and V = 922.80(9) Å3 at ambient temperature. The A and M(4) sites split into A(m) (K+), A(2) (Na+), and M(4’) (Mn2+) subsites, respectively. Among the octahedrally coordinated C group cations, Mn2+ orders strongly at the M(2) site. No significant violation of C2/m symmetry or change in the structure topology is detected at low temperature (R1=2.1%). The hjalmarite-bearing skarn formed at peak regional metamorphism, T ≥ 600°C, at conditions of high SiO2 activity and relatively low oxygen fugacity. The mineral name honors the Swedish geologist and mineralogist S.A. Hjalmar Sjögren (1856–1922).
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| 36. |
- Holtstam, Dan, et al.
(författare)
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Ulfanderssonite-(Ce), a new Cl-bearing REE silicate mineral species from the Malmkärra mine, Norberg, Sweden
- 2017
-
Ingår i: European journal of mineralogy. - : Schweizerbart. - 0935-1221 .- 1617-4011. ; 29:6, s. 1015-1026
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Tidskriftsartikel (refereegranskat)abstract
- Ulfanderssonite-(Ce) is a new mineral (IMA 2016-107) from the long-abandoned Malmkärra iron mine, one of the Bastnäs-type Fe-rare earth element (REE) deposits in the Bergslagen ore region, central Sweden. It is named for Ulf B. Andersson, a Swedish geologist and petrologist. In the type specimen, the mineral occurs with västmanlandite-(Ce), bastnäsite-(Ce), phlogopite, talc, magnetite, pyrite, fluorbritholite-(Ce) and scheelite. Ulfanderssonite-(Ce) forms pinkish, translucent subhedral grains, 100-300 mu m, in aggregates up to 2 mm. Fracture is uneven, and there is an indistinct cleavage parallel (001). Mohs' hardness is 5-6, D-calc = 4.97 g cm(-3). Optically, ulfanderssonite-(Ce) is nonpleochroic, biaxial negative, with 2V(meas) = 55 degrees and n(calc) = 1.82. The ideal composition is Ce15CaMg2(SiO4)(10)(SiO3OH)(OH,F)(5)Cl-3. Electron microprobe and LA-ICP-MS chemical analyses yielded (in wt%) La2O3 11.87, Ce2O3 30.98, Pr2O3 3.99, Nd2O3 17.14, Sm2O3 2.81, Eu2O3 0.18, Gd2O3 1.15, Dy2O3 0.30, Tb2O3 0.10, Y2O3 1.11, CaO 2.26, FeO 0.02, MgO 1.97, P2O5 0.08, SiO2 19.13, H2Ocalc 1.07, F 1.09, Cl 2.89, O=(F, Cl) -1.10, sum 97.04. The five strongest powder X-ray diffraction lines are [I(%) d(obs) (angstrom) (hkl)]: 100 2.948 (- 421), 47 2.923 (204), 32 2.660 (- 225), 26 3.524 (40-1), 25 1.7601 (6-23). Ulfanderssonite-(Ce) is monoclinic, Cm, with a = 14.1403(8), b = 10.7430(7), c = 15.498(1) angstrom, b = 106.615(6)degrees and V = 2256.0 (2) angstrom 3 for Z = 2. The crystal structure has been solved by direct methods and refined to R-1 = 2.97% for 5280 observed reflections. It consists of a regular alternation of two layers, designated A and B, along the c-axis: A (ca. 9 angstrom thickness), with composition [(Ce8Ca) MgSi7O22(OH, F) 4](8+), and B (ca. 6.5 angstrom), with composition [Ce7MgSi4O21(OH, F)(2)Cl-3](8); the A layer is topologically and chemically closely related to cerite-(Ce). A FTIR spectrum shows strong absorption in the region 2850-3650 cm(-1), related to the presence of OH stretching bands. Ulfanderssonite-(Ce) is interpreted as a primary mineral at the deposit, along with the more common fluorbritholite-(Ce), formed by a magmatic-hydrothermal fluid with REE, Si, F and Cl ion complexes reacting with dolomite marble. The presence of ulfanderssonite-(Ce) is direct evidence of a Cl-rich mineral-forming aqueous solution, normally not reflected in the composition of skarn minerals in Bastnäs-type deposits.
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| 37. |
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| 38. |
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| 39. |
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| 40. |
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| 41. |
- Karlsson, Andreas, 1986-, et al.
(författare)
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Adding complexity to the garnet supergroup: monteneveite, Ca3Sb5+2(Fe3+2Fe2+)O12, a new mineral from the Monteneve mine, Bolzano Province, Italy
- 2020
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Ingår i: European Journal of Mineralogy. - : Copernicus GmbH. - 0935-1221 .- 1617-4011. ; 32:1, s. 77-87
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Tidskriftsartikel (refereegranskat)abstract
- Monteneveite, ideally Ca3Sb5+2(Fe3+2Fe2+)O12, is a new member of the garnet supergroup (IMA 2018-060). The mineral was discovered in a small specimen belonging to the Swedish Museum of Natural History coming from the now abandoned Monteneve Pb-Zn mine in Passiria Valley, Bolzano Province, Alto Adige (South Tyrol), Italy. The specimen consists of mainly magnetite, sphalerite, tetrahedrite-(Fe) and oxycalcioroméite. Monteneveite occurs as black, subhedral crystals with adamantine lustre. They are equidimensional and up to 400 μm in size, with a subconchoidal fracture. Monteneveite is opaque, grey in reflected light, and isotropic under crossed polars. Measured reflectance values (%) at the four COM wavelengths are 12.6 (470 nm), 12.0 (546 nm), 11.6 (589 nm) and 11.4 (650 nm). The Vickers hardness (VHN100/ is 1141 kgmm-2, corresponding to H D 6:5-7, and the calculated density is 4.72(1) g cm-3. A mean of 10 electron microprobe analyses gave (wt %) CaO 23.67, FeO 3.75, Fe2O3 29.54, Sb2O5 39.81, SnO2 2.22, ZnO 2.29, MgO 0.15, MnO 0.03 and CoO 0.03. The crystal chemical formula calculated on the basis of a total of eight cations and 12 anions, and taking into account the available structural and spectroscopic data, is (Ca2:97Mg0:03)6D3:00 (Sb5+1.73Sn4+0.10Fe3+0.17)6D2.00(Fe3+2.43Fe2+0.37Zn0:20)6D3:00O12. The most significant chemical variations encountered in the sample are related to a substitution of the type Y Sn4CCZFe3CY Sb5CCZFe2C. Mössbauer data obtained at RT and 77K indicate the presence of tetrahedrally coordinated Fe2C. Raman spectroscopy demonstrates that there is no measurable hydrogarnet component in monteneveite. The six strongest Bragg peaks in the powder X-ray diffraction pattern are [d (Å), I (%), (hkl)]: 4.45, 100, (220); 3.147, 60, (400); 2.814, 40, (420); 2.571, 80, (422); 1.993, 40, (620); 1.683, 60, (642). Monteneveite is cubic, space group Ia-3d, with a D 12:6093(2) Å, V D 2004:8(1)Å3, and Z D 8. The crystal structure was refined up to R1 D 0:0197 for 305 reflections with Fo 4.Fo/ and 19 parameters. Monteneveite is related to the other Ca-, Sb- and Fe-bearing, nominally Si-free members of the bitikleite group, but it differs in that it is the only known garnet species with mixed trivalent and divalent cations (2 V 1) at the tetrahedral Z site. Textural and mineralogical evidence suggests that monteneveite formed during peak metamorphism (at ca. 600 C) during partial breakdown of tetrahedrite-(Fe) by reactions with carbonate, under relatively oxidizing conditions. The mineral is named after the type locality, the Monteneve (Schneeberg) mine. © Author(s) 2020.
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| 42. |
- Konrad-Schmolke, Matthias, 1970, et al.
(författare)
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Compositional re-equilibration of garnet: the importance of sub-grain boundaries
- 2007
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Ingår i: European journal of mineralogy. - 0935-1221 .- 1617-4011. ; 19:4, s. 431-438
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Tidskriftsartikel (refereegranskat)abstract
- Garnets from meta-granitoid high pressure rocks (Sesia Zone, Western Alps) show complex internal sub-grain textures in electron forescatter images. All investigated garnets consist of a large number of sub-grains with different shapes and sizes. Some garnets exhibit a sub-texture with very fine-grained (<20µm) sub-grains in their cores overgrown by palisade-like sub-grains in the rims. Sub-grain boundaries in these garnets have enabled diffusive element exchange between the garnet core and the surrounding matrix. Compositional mapping reveals zonation patterns of Mg that indicate modification of the garnet composition during prograde metamorphism. The extent of diffusional re-equilibration is dependent on sub-grain size and element diffusivities. Our samples show that XMg is strongly influenced by diffusion along the sub-grain boundaries, whereas apparently slow diffusing elements, such as Ca, Ti and Y preserve their original concentric zonation pattern. This differential re-equilibration leads to very complex chemical zonation that cannot be easily interpreted in terms of simple prograde growth zonation or of normally-applied spherical diffusion models. The observation that almost all garnets in the investigated samples exhibit a sub-grain pattern suggests this might be a common feature in high pressure/low temperature rocks.
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| 43. |
- Majka, Jaroslaw, et al.
(författare)
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Pressure-temperature estimates of the blueschists from the Kopina Mt., northern Bohemian Massif, Poland - constraints on subduction of the Saxothuringian continental margin
- 2016
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Ingår i: European journal of mineralogy. - : E SCHWEIZERBARTSCHE VERLAGSBUCHHANDLUNG. - 0935-1221 .- 1617-4011. ; 28:6, s. 1047-1057
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Tidskriftsartikel (refereegranskat)abstract
- The blueschist occurrence at the Kopina Mt. is situated at the eastern margin of the Karkonosze Izera Massif in the West Sudetes of the northern Bohemian Massif. Metabasic rocks with continental crust affinity occur as lenses within the prevailing metasediments. The metabasites consist mainly of garnet, blue amphibole, epidote, chlorite-I, titanite, hematite and quartz forming the high-pressure assemblage. Synkinematic garnet exhibits prograde zoning, a feature allowing for assessment of the prograde course of the pressure temperature (P-T) path. Phase equilibrium modelling has been used to estimate prograde and peak metamorphic conditions. Based on the P-T pseudosections, calculated in the system Na2O-CaO-K2O-FeO-MgO-MnO- Al2O3-SiO2-H2O-TiO2-O-2 (NCKFMMnASHTO), the garnet + glaucophane + epidote + chlorite + white mica(?) + Fe oxide + quartz titanite assemblage was formed between 12-15 kbar and 480-520 degrees C. These results are based on garnet and Na-amphibole compositional isopleths. Garnet shows a prograde zoning expressed by the rapid rim-ward decrease of spessartine, moderate increase of almandine and as light increase of other components. It is inferred here that white mica must have decomposed to secondary albite chlorite-II K-feldspar. The obtained results point to the formation of the Kopina blueschists along a low-temperature P-T gradient of 8-10 degrees C/km, typical of rocks from a subduction exhumation channel. We postulate that the Kopina blueschists were formed in a subduction system developed along the eastern termination of the Saxothuringian Ocean and operating beneath the Tepla Barrandian upper plate. When combined with previous data on continental crust affinity for the protolith, our results demonstrate a derivation of the Kopina blueschists from subducted part of the Saxothuringian margin.
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| 44. |
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| 45. |
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| 46. |
- Mohammad, Y O, 7602, et al.
(författare)
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Mg-staurolite and kyanite inclusions in metabasic garnet amphibolite from the Swedish Eastern Segment: evidence for a Mesoproterozoic subduction event.
- 2011
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Ingår i: European Journal of Mineralogy. - 0935-1221. ; 23:4, s. 609-631
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Tidskriftsartikel (refereegranskat)abstract
- We present evidence that the 1674 Ma Bora°s Mafic Intrusion of the Swedish Eastern Segment experienced high-pressure metamorphism related to a Sveconorwegian subduction-exhumation cycle. Mg-rich staurolite is found as inclusions in garnet in metaluminous amphibolites. The inclusion assemblages include staurolite (XMg 0.34–0.40), kyanite, euhedral anorthite, clinozoisite and quartz. The thermodynamic packages winTWQ and Theriak-Domino were used to investigate the P-T conditions of the matrix and inclusion mineral parageneses. The bulk composition of the rock does not have a stability field for staurolite-bearing parageneses. In our samples minerals of an eclogite-facies paragenesis became isolated from the whole rock in the first stage as inclusions in garnet. High Zn levels in the staurolite (0.6–1 wt% ZnO) show that it must have formed as either chloritoid or staurolite, both of which concentrate Zn. Euhedral anorthite inclusions have trace-element compositions including high Sr and insignificant Eu anomalies, which support their interpretation as pseudomorphs after lawsonite in plagioclase-out conditions. Rutile lamellae in the garnet are also indicative of a high-pressure origin. Calculated phase diagrams show that the most likely original paragenesis was garnet þ clinopyroxene þ Mg-rich chloritoid þ lawsonite þ kyanite þ quartz, which has a stability field for the whole-rock composition at 600 °C and 2.23–2.45 GPa. These conditions correspond to depths greater than 75 km, thus the Bora°s Mafic Intrusion was situated in the mantle at that time, implying subduction of the crustal block in which it was situated. The minerals now observed in the inclusions and in the rock matrix formed under amphibolite-facies conditions at lower pressures of 0.6–0.9 GPa and slightly increased temperatures around 650 °C, reflecting rapid exhumation from the mantle. Sm-Nd dating of garnet gives 957.1 ° 9.4 Ma, consistent with less precise Lu-Hf data, and represents either garnet growth during subduction or resetting during exhumation. Our investigations of staurolite in amphibolites documented in the literature show that staurolite cannot form in equilibrium with amphibolitefacies parageneses in normal metabasic rocks, which always have metaluminous compositions. A two-stage process is required in which a peraluminous assemblage with kyanite and possibly chloritoid first forms, due to plagioclase-out reactions in eclogite-facies conditions. Staurolite forms in the second stage during exhumation as pressure decreases, in domains which are not in contact with the common amphibolite-facies assemblage, for example by hydration reactions involving kyanite and garnet or by breakdown of chloritoid at higher temperatures. The pressures estimated for garnet growth and the development of inclusions correspond to minimum depths of 75–83 km (for basaltic or granitic overburden) and the Bora°s Mafic Intrusion is an integral part of the Eastern Segment in which retrograde eclogite metabasic bodies occur within orthogneisses in at least four other localities. This implies that a major part of the Eastern Segment experienced a high-pressure metamorphic event and the entire block of continental crust was involved in a subduction-exhumation cycle during the Sveconorwegian orogeny.
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| 47. |
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| 48. |
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| 49. |
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| 50. |
- Perchiazzi, Natale, et al.
(författare)
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Gabrielsonite revisited: crystal-structure determination and redefinition of chemical formula
- 2018
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Ingår i: European journal of mineralogy. - : Schweizerbart. - 0935-1221 .- 1617-4011. ; 30:6, s. 1173-1180
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Tidskriftsartikel (refereegranskat)abstract
- A reinvestigation of gabrielsonite from the holotype specimen from Långban, central Sweden, using single-crystal synchrotron X-ray diffraction, electron-microprobe techniques and Fourier-transform infrared (FTIR) spectroscopy, Raman and Mössbauer spectroscopies show that the mineral is an anhydrous Fe3+-bearing arsenite and not a hydrous Fe2+-bearing arsenate, as originally proposed. The revised ideal chemical formula of gabrielsonite is PbFe3(As3+O3)O. The mineral is related to the descloizite supergroup, but it differs through the valencies of the non-Pb cations Fe (M3+ vs. M2+) and As (3+ vs. 4+) and through lower coordination of Pb (4 vs. 7–8) and As (3 vs. 4). The redefinition of gabrielsonite (proposal 17-G) has been approved by the Commission on New Minerals, Nomenclature and Classification (CNMNC) of the International Mineralogical Association.
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