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Published: 20 August 2018
European Journal of Mineralogy, Volume 30, pp 237-251; https://doi.org/10.1127/ejm/2017/0029-2690

Abstract:
Uranyl-oxide hydroxy-hydrates (UOH) represent one of the most structurally and chemically complex families of naturally occurring U6+ phases.To date, about 28members are known as mineral species and a dozen others have been synthesized under laboratory conditions. The majority of these have been structurally characterized, showing an extraordinary complexity despite their relatively simple chemical composition; U, Pb, O and H are mostly the major constituents. Both the structural and chemical complexity of UOH minerals were determined with the program TOPOS, using complexity parameters that provide Shannon information content per atom and per unit cell and per formula unit.The average content per unit cell,1159 bits/cell shows that UOH minerals are extraordinary complex; this is in line with (1) the high coordination diversity, considering the transition of U4+ to U6+ during oxidation-hydration weathering of uraninite that leads to the formation of UOH phases; (2) incorporation of a large amount of H+, in the form of H2O and (OH)-; (3) incorporation of other elements during weathering,mostly K+, Pb2+ or Ca2+. The simplest UOH mineral is vandenbrandeite, triclinic, Cu (UO2)(OH)4, with 86 bits/cell. The most complex UOH mineral is vandendriesscheite, orthorhombic Pb1.5[(UO2)10O6(OH)11](H2O)11, with 4296 bits/cell, which owes its structural complexity to the presence of a large proportion of H2O/OH and several symmetrically unique U sites in the structure. The general trend of the early-forming UOH minerals is a high molar proportion of U and H2O/OH and lower proportion of metal cations. This leads in general to their complex character. The increase in complexity (both structural and chemical) is also related to the presence of metal cations in the structure with distinct stereochemistry, such asK+, Fe2+, Ca2+ or Pb2+. The overall trend is a steady increase of complexity (both structural and chemical) during continuous alteration. A discussion of occurrence trends and UOH complexity is given. One of the most complex structures among UOHs is schoepite, [(UO2)8O2(OH)12](H2O)12 (∼2593 bits/cell), which is reported from various localities worldwide. The relatively common occurrence of schoepite is probably because it is a very early alteration product, which is (1) complex and (2) easily distinguishable.
, Ágnes Takács, , , Jarmila Luptáková, Tamás Váczi, Peter Antal
Published: 1 December 2017
European Journal of Mineralogy, Volume 29, pp 995-1004; https://doi.org/10.1127/ejm/2017/0029-2672

Abstract:
Javorieite, KFeCl3, is a new mineral, commonly hosted by salt melt inclusions enclosed in vein quartz in the Biely Vrch porphyry gold deposit, in the Central Slovakia Volcanic Field in the Western Carpathians. The mineral name refers to the Javorie stratovolcano, which hosts most porphyry gold systems in this volcanic field. Within the inclusions, javorieite occurs in the form of small (up to 15μm) green anhedral crystals with high relief, which melt in the range 320–338 °C when heated. It is extremely hygroscopic and readily oxidised if exposed to the air. The daughter mineral was identified through comparison with the Raman spectra of the synthetic analogue, and through data obtained with the FIB-SEM-EBSD analytical technique. The combination of the three independent analytical tools on three different inclusions proved the match in chemistry and crystallography with synthetic KFeCl3. Javorieite is orthorhombic, the unit-cell parameters are a = 8.715(6)Å, b = 3.845(8)Å, c = 14.15(3)Å, V = 474.16(3)Å3, Z = 4. Furthermore, the experimental data in the NaCl–KCl–FeCl2 system agree with the microthermometric behaviour of javorieite. The presence of javorieite in three other localities in this volcanic field was established by Raman spectroscopy. The distinctive Raman spectrum of javorieite (main bands at 66–69, 108–109, 119–120, 134–135, 235–237cm-1) can help in future studies of salt melt inclusions worldwide, including a quick recognition of shallow porphyry systems that can be potentially enriched in gold.
, , Daniele Regis, , Marco E. Ciriotti, Roberto Compagnoni
Published: 1 September 2018
European Journal of Mineralogy, Volume 30, pp 545-558; https://doi.org/10.1127/ejm/2017/0029-2692

Abstract:
Magnesiobeltrandoite-2N3S, ideally Mg6Al20Fe23+O38(OH)2, is a new member of the högbomite supergroup of minerals. It occurs in magnesian chloritites of a metamorphosed layered mafic complex in the Etirol-Levaz continental slice, middle Valtournenche, Aosta Valley, Italy. Magnesiobeltrandoite-2N3S grows in a fine-grained chlorite matrix associated as inclusions to relict pre-Alpine hercynite spinels and dolomite in cm- to dm-long darker boudins, which are cut by corundum + clinochlore ± dolomite veins. It occurs as subhedral to euhedral black crystals (∼50–400μm), dark reddish-brown in thin section. It shows dark brown streak and vitreous lustre. It is brittle, with no cleavage observed and uneven fracture. Mohs hardness ≈6–6½. Dcalc = 3.93 g · cm-3. It shows no fluorescence under UV radiation and no cathodoluminescence. The mineral is optically uniaxial (–) with an estimated mean refractive index of ca. 1.80. Pleochroism is weak with ε = deep reddish brown (along c axis) and ω = reddish brown (⊥ c). Absorption is E > O. The Raman spectrum shows a weak and strongly polarized broad OH-characteristic absorption centred at 3364 cm-1. Electron microprobe analysis combined with Synchrotron Mössbauer source spectrometry yielded the following empirical formula based on 40 anions per formula unit (pfu) [Al18.36Mg3.96Fe2+2:52Fe3+2:08Ti0.56Cr0.40Zn0.06V3+0:03Mn0.02]Σ28O38(OH)2. The ideal formula is Mg6Al20Fe23+O38(OH)2. The eight strongest lines in the X-ray powder diffraction pattern are [dobs/A (I) (h k l)]: 2.858 (42) (1 1 0), 2.735 (51) (1 0 7), 2.484 (46) (0 1 8), 2.427 (100) (1 1 5), 1.568 (29) (1 2 8), 1.514 (30) (0 2 12), 1.438 (42) (2 0 13), and 1.429 (72) (2 2 0). The crystal structure of magnesiobeltrandoite-2N3S [P3-m1, a = 5.7226(3), c = 23.0231(9)Å, V = 652.95(5)Å3] was refined from X-ray single-crystal data to R1 = 0.022; it is isostructural with magnesiohögbomite-2N3S.
Xiaoyan Li, Chao Zhang, Harald Behrens, François Holtz
Published: 1 February 2018
European Journal of Mineralogy, Volume 30, pp 33-44; https://doi.org/10.1127/ejm/2017/0029-2689

Abstract:
We present experimental results constraining the partitioning of fluorine (F) between titanite and metaluminous silicate melt under H2 O-saturated conditions at 50–200 MPa, 875–925°C. Resulting experimental melts are metaluminous with ASI values [aluminium saturation index, calculated as molar Al2 O3 /(CaO + Na2 O + K2 O)] falling in the range 0.68–0.97. Titanite crystals and coexisting melts have F contents that vary from 0.2 to 2.6 wt% and from 0.2 to 3.2 wt%, respectively. The calculated proportion of the F–O substitution is within 0.02–0.28 per formula unit, which is predominantly compensated by the substitution of Al and Fe3+ for Ti, as well as a subordinate amount of Ti– Mg2+ substitution. The mass-ratio partition coefficient DFTtn melt is within 0.5–1.2, and there is little influence of pressure under the conditions investigated. However, the potential effect of temperature needs further investigation. DFTtn melt is positively correlated with melt ASI, and can be predicted using the following relation: DFTtn melt = 2.26 ASI 1.05. This equation is valid only for metaluminous melts (ASI D FTtn melt is related to structural properties of F-bearing melts, which can incorporate higher F concentrations at lower ASI. Assuming that the high-Ti titanite investigated here is subject to ideal mixing, we calculated a Margules parameter (WFmelt) of 48.6 ± 4.3 kJ/mol for F in silicate melt with a symmetric binary mixing model. The high value of WFmelt confirms that O– F mixing in silicate melt is far from ideal. The reliability of using of DFTtn melt to calculate melt F contents has been checked by investigating plutonic rocks of the Liujiawa pluton in the Dabie orogen of eastern China. Our new estimates of melt F content are consistent with those derived from amphibole, biotite and apatite compositions.
Beate Orberger, Christiane Wagner, Alina Tudryn, Benoit Baptiste, Richard Wirth, Rachael Morgan, Serge Miska
Published: 1 December 2017
European Journal of Mineralogy, Volume 29, pp 971-983; https://doi.org/10.1127/ejm/2017/0029-2679

Abstract:
The low-grade carbonate banded iron formation of the Aguas Claras mine, from the transition of the Caûe to the Gandarela Formation (2.4 Ga, Itabira Group, Brazil), is composed of porous and microsparitic dolomite, quartz, iron oxides and (oxy)hydroxides. Iron oxides occur as bands, veins and as inclusions in the dolomite crystals, whereas iron (oxy)hydroxides only occur as inclusions. Combined mineralogical analyses (X-ray diffraction, Raman spectroscopy, focused-ion-beam thinning and transmission electron microscopy) identified the inclusions in porous dolomite as hematite and minor goethite and/or ferrihydrite, whereas microsparitic dolomite only hosts hematite. Curie balance analysis on whole rock reveals that, at temperatures between ∼680 °C and ∼900 °C, hematite and iron (oxy)hydroxide inclusions react with the surrounding dolomite resulting in the assemblage: magnesioferrite (MgFe2O4), srebrodolskite (Ca2Fe2O5), lime (CaO), portlandite (Ca(OH)2) and periclase (MgO), whereas hematite and pure dolomite do so only at ∼900 °C. This difference is an indirect argument for the presence of iron hydroxide inclusions within the dolomite. The inclusions are either single crystals or form clusters in pores. The fast-Fourier-transform diffraction pattern of one single crystal can be indexed as goethite and ferrihydrite. This finding suggests an incipient solid-state transformation of ferrihydrite to goethite rather than a dissolution-precipitation process. It is suggested that the clustered hematite and the goethite/ferrihydrite precipitated from Fe- and Si-bearing fluid inclusions, which were trapped during early diagenesis at about 2.4 Ga under oxygenated conditions. Microstructural evidence (e.g. dislocations in dolomite from hematite inclusions) point to maximum T<420 °C. The preservation of goethite/ferrihydrite clustered inclusions during this low-temperature event may be due to their silica contents increasing their stability.
Sergey V. Krivovichev, Vladimir G. Krivovichev, Robert M. Hazen
Published: 20 August 2018
European Journal of Mineralogy, Volume 30, pp 231-236; https://doi.org/10.1127/ejm/2018/0030-2694

Abstract:
Correlations between chemical and structural complexities of minerals were analysed using a total of 4962 datasets on the chemical compositions and 3989 datasets on the crystal structures of minerals. The amounts of structural and chemical Shannon information per atom and per unit cell or formula unit were calculated using the approach proposed by Krivovichev with no H-correction for the minerals with unknown H positions. Statistical analysis shows that there are strong and positive correlations (R>2>0.95) between the chemical and structural complexities and the number of different chemical elements in a mineral. Analysis of relations between chemical and structural complexities provides a strong evidence that there is an overall trend of increasing structural complexity with the increasing chemical complexity. Following Hazen, four groups of minerals were considered that represent four eras of mineral evolution: “ur-minerals”, minerals from chondritic meteorites, Hadean minerals, and minerals of the post-Hadean era. The analysis of mean chemical and structural complexities for the four groups demonstrate that both are gradually increasing in the course of mineral evolution. The increasing complexity follows an overall passive trend: more complex minerals form with the passage of geological time, yet the simpler ones are not replaced. The observed correlations between the chemical and structural complexities understood in terms of Shannon information suggest that, at a first approximation, chemical differentiation is a major force driving the increase of complexity of minerals in the course of geological time. New levels of complexity and diversification observed in mineral evolution are achieved through the chemical differentiation, which favours local concentrations of particular rare elements and creation of new geochemical environments.
Yulia A. Pankova, , , Igor V. Pekov
Published: 20 August 2018
European Journal of Mineralogy, Volume 30, pp 277-287; https://doi.org/10.1127/ejm/2018/0030-2695

Abstract:
The crystal structure of ginorite, Ca2[B14O20(OH)6]·5H2O, from the Chelkar salt dome, western Kazakhstan, has been refined at 150(2) and 296(2) K. The mineral is monoclinic, P21/c, unit-cell parameters are (at 150/296 K): a = 12.738(1)/12.728(1), b = 14.240(1)/14.303(1), c = 12.750(1)/ 12.755(1)Å, β = 101.163(2)/101.147(2)°, V = 2268.9(4)/2278.3(4)Å3, Z = 4. The crystal structure is isotypic to that of strontioginorite and is based upon 2-dimensional anionic layers with the composition [B14O20(OH)6]4-. The layers are coplanar to (0 1 0) and are composed of BO4 tetrahedra and BO3 triangles. The fundamental building block (FBB) for the crystal structures of ginorite and strontioginorite consists of eight BO3 triangles and six BO4 tetrahedra. The adjacent FBBs are linked by sharing O atoms to form layers that possess open nine-membered rings centered by the M1 and M2 metal atoms. In the crystal structure of strontioginorite, the M1 and M2 sites are occupied by Sr and Ca, respectively, whereas, in ginorite, both sites are occupied by Ca. The Ca↔Sr substitution affects the geometry of the M1O8 polyhedron significantly, with the difference |Δ| between the Sr–O and Ca–O bond lengths up to 0.157Å. The dimensional reduction, structural and chemical complexity of 45 minerals and inorganic compounds of the CaO–B2O3–H2O system have been analyzed using ternary diagrams. The structures with 0-dimensional structural units (finite clusters) constitute 53.3% (24) of all structures in the system, whereas 1-, 2- and 3-dimensional borate polyanions have been observed in 15.6% (7), 20.0% (9) and 11.1% (5) of all structures in the system, respectively. The average structural complexity for the 42 B-bearing phases in the CaO–B2O3–H2O system is 353 bits/cell agrees well with the average complexity of 340 bits/cell for all boron minerals. Ginorite belongs to the class of very complex structures (1536.000 bits/cell) and is the second in complexity in the system after alfredstelznerite, Ca4(H2O)4[B4O4(OH)6]4·15H2O (4026.707 bits/cell). In general, structural and chemical complexities correlate with each other and indicate the presence of the high-complexity areas in the H2O dominant part of the diagram, in a band between ca. 10 and 20 mol% CaO.
Ray MacDonald, Krzysztof Nejbert, , Edyta Jurewicz
Published: 1 February 2018
European Journal of Mineralogy, Volume 30, pp 135-147; https://doi.org/10.1127/ejm/2017/0029-2693

Abstract:
The occurrence of chevkinite-group minerals (CGM), zirconolite and Nb-rich ilmenite is reported in Miocene high-K trachyandesites from the Uherský Brod area, Czech Republic, their occurrence reflecting the high Nb and Zr abundances in the host rocks. All three were late-magmatic phases, crystallizing from silicic residual melts. Strong zonation in some crystals is ascribed mainly to kinetic factors and in the case of the CGM by the replacement of less Fe-rich, more calcic ("perrieritic") compositions by compositions richer in Fe and poorer in Ca ("chevkinitic") as temperatures fell during crystallization. Zirconolite has high ThO2 (7.75 wt%) and UO2 (3.78 wt%) abundances and is commonly zoned, with significant fractionation of Th from U and within the LREE. The minerals may have crystallized at relatively high f O2, low pH2O, and at temperatures around 840°C. Zirconolite was stabilized relative to zircon by the Ti–Ca-rich nature of the melts and to baddeleyite by the high SiO2 activity. Formation of Zr-bearing titanite, as recorded in other potassic suites, was precluded by the preferential entry of Ti into the CGM.
Ulf Hålenius, Frédéric Hatert, Marco Pasero, Stuart J. Mills
Published: 10 October 2017
European Journal of Mineralogy, Volume 29, pp 777-781; https://doi.org/10.1127/ejm/2017/0029-2680

Luca Bindi, Xiande Xie
Published: 1 February 2018
European Journal of Mineralogy, Volume 30, pp 165-169; https://doi.org/10.1127/ejm/2017/0029-2684

Abstract:
Shenzhuangite (IMA 2017-018), NiFeS2, is a new mineral species found in the shocked Suizhou L6 chondrite. The mineral is closely associated with forsteritic olivine, pyroxene, plagioclase glass (maskelynite), taenite and troilite. It is opaque, and in reflected light shenzhuangite is weakly anisotropic with light brown to greenish rotation tints. Internal reflections are absent. The reflectance COM values (air, R1, and R2, in %) are: 24.8, 26.0 (471.1 nm); 34.9, 36.2 (548.3 nm); 37.7, 39.1 (586.6 nm); 40.4, 41.1 (652.3 nm). The average result of 4 electron-microprobe analyses is Ni 22.37(55), Fe 30.87(67), Cu 10.88(22), Co 0.07(4), S 35.42(58), total 99.61 wt%. The empirical formula (based on 4 atoms pfu and assuming the crystal-chemical exchange: Cu++Fe3+↔Ni2++Fe2+) is (Ni2+0:69Cu+0:31)(Fe2+0:69Fe3+0:69 0:31)S2.00. The simplified formula is NiFeS2, which requires Ni 32.85, Fe 31.26, S 35.89, total 100.00 wt%. Shenzhuangite is tetragonal, space group I4-2d, with unit-cell parameters: a = 5.3121(4), c = 10.4772(7)Å, V = 295.65(4)Å3, c:a = 1.9723, Z = 4. The five strongest observed X-ray powder-diffraction lines [d in Å(I/I0) (h k l)] are: 3.05 (100) (1 1 2), 1.875 (20) (2 2 0), 1.591 (25) (3 1 2, 1 1 6), 1.215 (10) (3 3 2, 3 1 6), 1.080 (10) (4 2 4). The crystal structure showed that shenzhuangite is the Ni-analogue of chalcopyrite. It likely formed as alteration of pre-existing taenite when pS2/pO2 ratios allowed sulfurization of the FeNi metal. Shenzhuangite is named in honour of Prof. Shangyue Shen and Prof. Xiaoli Zhuang who first discovered the Ni-rich variety of chalcopyrite in the Suizhou meteorite.
Edward S. Grew, , Linus Ros, Per Kristiansson, Mickey E. Gunter, , Robert B. Trumbull, Martin G. Yates
Published: 20 August 2018
European Journal of Mineralogy, Volume 30, pp 205-218; https://doi.org/10.1127/ejm/2017/0029-2686

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) (589.3nm). 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) wt%; Cl 0 (0.01). 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)Σ1.00Y(□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 MoKα 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 both micas 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 2O and 1.0–1.1 wt% and 1.4–1.5 wt% Rb2O, respectively. Other minerals include spessartine (e.g., Sps93Alm4Grs3) in scattered grains up to 0.5mm across andmonazite.Oxides occur sparsely inmuscovite, rarely in lepidolite, as grains up to 11μm long, including fluorcalciomicrolite, columbite-(Mn) with Nb > 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–fluor-elbaite assemblage. Given the 2990 ± 43MaRb–Sr isochron and 3074 ± 4Maevaporation 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.
Lisard Torró, Robert F. Martin, Dirk Schumann, Julia Cox, Salvador Galí Medina,
Published: 1 February 2018
European Journal of Mineralogy, Volume 30, pp 45-59; https://doi.org/10.1127/ejm/2017/0029-2682

Abstract:
Megacryst-bearing alkaline basic rocks of Cenozoic age occur in scattered centers in western Europe, from the Rhine graben to southern Spain.We focus on two volcanic fields, La Garrotxa in northeastern Spain, and in particular the Pomareda and Roca Negra monogenetic cones in the Olot suite, and the Chuquet Genestoux occurrence, Puy-de-Dôme, France. The explosive emplacement of the basanitic magma favored the entrainment of xenoliths of clearly crustal and mantle origin in both suites.We seek to characterize the megacrysts of scapolite and andesine. The sulfate-bearing scapolite crystallized in space group I4/m rather than the expected P42/n, likely because of disorder in the sulfate groups. The megacrysts in both suites are part of an igneous mantle-derived assemblage, to judge from δ18O values, supported by δ13OC and δ34OS values of the sulfate-bearing scapolite. We document signs of flash melting in both scapolite and plagioclase megacrysts from Pomareda. A white rim of up to 2mm on the scapolite megacrysts consists of skeletal individuals of calcic plagioclase; these crystals contain wollastonite, silvialite, diopside, and myriads of vacuoles. The andesine megacryst also underwent melting at its margin, to a sieve-textured assemblage of neoformed labradorite, glass, and free silica. The flash melting of individual megacrysts encapsulated in basanitic melt, documented here for the first time, has produced metastable products. Progress of the melting reactions was arrested by a thermal quench upon eruption.
Min-Yu Lin, Yen-Hua Chen, Jey-Jau Lee, Hwo-Shuenn Sheu
Published: 1 February 2018
European Journal of Mineralogy, Volume 30, pp 77-84; https://doi.org/10.1127/ejm/2017/0029-2681

Abstract:
Iron sulfides were synthesized via a co-precipitation method. In addition, synchrotron-radiation experiments were performed under a range of pH and temperature conditions (up to 100 °C) to compare the results of in situ and ex situ crystal growth investigation of iron sulfides. In acidic environments, H2S acts as an oxidant, oxidizing Fe2+ to Fe3+ and allowing formation of greigite frommackinawite. However, under neutral conditions, due to very low H2S concentrations, the oxidant may be S (instead of H2S), allowing mackinawite to transform into greigite. Both mackinawite and magnetite were present under alkaline conditions, with possible transitions of Fe2+ + 2OH- → Fe(OH)2, followed by 3Fe(OH)2 → Fe3O4 + 2H2O + H2. In situ X-ray diffraction results indicate that the mineral transformation rate under acidic conditions is faster than under neutral and alkaline conditions. This means that acid environments can enhance rapid phase transformation of iron sulfides. The results under different experimental conditions suggest that there is a variety of formation pathways for iron-sulfide minerals owing to the presence of different oxidants in different geochemical environments.
Ferdinando Bosi, Henrik Skogby,
Published: 15 December 2017
European Journal of Mineralogy, Volume 29, pp 889-896; https://doi.org/10.1127/ejm/2017/0029-2631

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–.
, José J. Elvira, , , Núria Oriols, Martí Busquets-Masó, Sergi Hernández
Published: 15 December 2017
European Journal of Mineralogy, Volume 29, pp 915-922; https://doi.org/10.1127/ejm/2017/0029-2630

Abstract:
The new mineral abellaite (IMA 2014-111), ideally NaPb2 (CO3)2 (OH), is a supergene mineral that was found in one of the galleries of the long-disused Eureka mine, in the southern Pyrenees (Lleida province), Catalonia, Spain. Abellaite is found as sparse coatings on the surface of the primary mineralization, it forms subhedral crystals not larger than 10μm as well as larger pseudohexagonal platelets up to ~ 30μm. Individual crystals commonly have a tabular to lamellar habit and form fairly disordered aggregates. The mineral is associated with a large number of primary minerals (roscoelite, pyrite, uraninite, coffinite, 'carbon', galena, sphalerite, nickeloan cobaltite, covellite, tennantite and chalcopyrite) and supergene minerals (hydrozincite, aragonite, gordaite, As-rich vanadinite andersonite, čejkaite, malachite and devilline). Abellaite is colourless to white, with a vitreous to nacreous lustre. The mineral is translucent, has a white streak and is non-fluorescent. The aggregates of microcrystals are highly friable. The calculated density using the ideal formula is 5.93 g/cm3. The chemical composition of the mineral (the mean of 10 electron microprobe analyses) is Na 3.88, Ca 0.29, Pb 72.03, C 4.17, O 19.47 and H 0.17, total 100.00 wt% (H, C and O by stoichiometry assuming the ideal formula). On the basis of 7 O atoms, the empirical formula of abellaite is Na0.96 Ca0.04 Pb1.98 (CO3)2 (OH). The simplified formula of the mineral is NaPb2 (CO3)2 (OH). The mineral is hexagonal, space group P 63 mc, a = 5.254(2), c = 13.450(5) Å, V = 321.5(2) Å3 and Z = 2. The strongest powder-diffraction lines [d in Å (I) (h k l)] are: 3.193 (100) (0 1 3), 2.627 (84) (1 1 0), 2.275 (29) (0 2 0), 2.242 (65) (0 2 1, 0 0 6), 2.029(95) (0 2 3). Abellaite has a known synthetic analogue, and the crystal structure of the mineral was refined by using crystallographic data of the synthetic phase. The mineral is named in honour of the mineralogist and gemmologist Joan Abella i Creus (b. 1968), who has long studied the deposits of the Eureka mine and who collected the mineral.
Paolo Orlandi, Cristian Biagioni, , Yves Moëlo, Werner H. Paar
Published: 10 October 2017
European Journal of Mineralogy, Volume 29, pp 713-726; https://doi.org/10.1127/ejm/2017/0029-2625

Abstract:
The new mineral species bernarlottiite, Pb12 (As10 Sb6)Σ16 S36, has been discovered in cavities of the Early Jurassic marbles from the Ceragiola quarry, Seravezza, Apuan Alps, Tuscany, Italy. Its name honours Bernardino Lotti (1847–1933) for his significant contribution to the knowledge of the geology of Tuscany and to the development of the Tuscan mining industry. It occurs as lead-grey acicular crystals up to 1 mm in length and few μm in width, with a metallic lustre, associated with Sb-rich sartorite. Under the ore microscope, bernarlottiite is white with abundant red internal reflections; pleochroism is weak in air, with shades of grey-blue. Anisotropism is distinct to strong, with greyish-bluish rotation tints. Reflectance percentages for the four COM wavelengths are [Rmin, Rmax (%), (l)]: 30.0, 37.5 (470 nm); 30.3, 37.3 (546 nm); 29.7, 36.8 (589 nm); and 29.3, 36.2 (650 nm). Electron-microprobe analyses, collected on two different grains, give (in wt%): Cu 0.09 (16), Pb 48.89 (1.26), As 17.48 (22), Sb 11.36 (10), S 23.11 (32), total 100.93 (1.38) (sample # 2987) and Pb 47.43 (26), As 14.56 (24), Sb 13.92 (18), S 22.64 (17), total 98.56 (44) (sample # 3819). On the basis of ΣMe = 28 atoms per formula unit, the chemical formulae are Cu0.07(12) Pb11.71(18) As11.59(21) Sb4.63(9) S35.78(48) and Pb11.92(6) As10.12 (14) Sb5.95(8) S36.76(32) for samples # 2987 and # 3819, respectively. The main diffraction lines, corresponding to multiple h k l indices, are [ d in Å (relative visual intensity)]: 3.851 (s), 3.794 (s), 3.278 (s), 3.075 (s), 2.748 (vs), 2.363 (s), and 2.221 (vs). The crystal structure study gives a triclinic unit cell, space group P 1, with a = 23.704 (8), b = 8.386 (2), c = 23.501 (8) Å, α = 89.91 (1), β = 102.93 (1),γ = 89.88 (1), V = 4553 (2) Å3, Z = 3. The crystal structure has been solved and refined to R1 = 0.088 on the basis of 7317 reflections with Fo >4 σ(Fo). Bernarlottiite is a new N = 3.5 homeotype of the sartorite homologous series, with a 3 a superstructure relative to that of baumhauerite. Its crystal structure can be described as being formed by 1:1 alternation of sartorite-type (N = 3) and dufrénoysitetype (N = 4) layers along c, connected by Pb atoms with tricapped trigonal prismatic coordination. Each layer results from the stacking of two types of ribbons along a, a centrosymmetric one alternating with two acentric ones. The three main building operators of the structure are (1) the interlayers As- versus -Pb crossed substitution, stabilizing the combined N = (3, 4) baumhauerite homologue, (2) the inter-ribbon Sb partitioning in the sartorite-type layer, with "symmetrization" of the Sb-rich ribbon, that induces the 3a superstructure, and (3) the common (As, Sb) polymerization through short (As, Sb)–S bonds.
, Márta Berkesi, Haemyeong Jung,
Published: 15 December 2017
European Journal of Mineralogy, Volume 29, pp 807-819; https://doi.org/10.1127/ejm/2017/0029-2658

Abstract:
Spinel-peridotite xenoliths, hosted in alkali basalts (~15 Ma), were collected from Adam's Diggings in the western margin of the Rio Grande Rift (RGR), New Mexico, USA. We selected five representative spinel-peridotite xenoliths, showing abundant fluid inclusions (FIs). Petrographic observations allowed the distinction of two generations of fluid-inclusion assemblages, both hosted in orthopyroxenes, namely Type-1 (earlier) and Type-2 (later). Both types of fluid inclusions were characterized combining microthermometry, high-resolution Raman micro-spectroscopy, and focused ion beam – scanning electron microscopy. The results of this study indicate that the timing and depth of entrapment, as well as the composition of trapped fluid were different between Type-1 and Type-2 FIs. The earlier fluid infiltration (C–O–N–S) happened before or during formation of exsolution lamellae and was trapped as Type-1 FIs in the cores of orthopyroxenes, whereas the later fluid in filtration (C– O–H–S) was trapped as Type-2 FIs after the formation of the orthopyroxene porphyroclasts with exsolution lamellae. The two fluid percolation events in the Adam's Diggings peridotites indicate the complexity of mantlefluids around the RGR. During ascent of the xenoliths within a basaltic lava, postentrapment reactions produced magnesite and quartz in Type-1 FIs and magnesite and talc in Type-2 FIs as reaction products of the fluid and its host mineral (orthopyroxene).
Delia-Georgeta Dumitraş
Published: 1 December 2017
European Journal of Mineralogy, Volume 29, pp 1055-1066; https://doi.org/10.1127/ejm/2017/0029-2655

Abstract:
Material from the type locality, the “dry” Cioclovina Cave, Şureanu Mountains, Romania, was re-examined in order to update the descriptive mineralogy of ardealite, a rare hydrated calcium acid phosphate sulfate. Ardealite from Cioclovina has a S/P ratio ranging between 1/0.87 and 1/0.98. Although S remains the main tetrahedral cation in the structure, P is consistently present at concentrations between 19.10 and 20.45 wt% P2O5 (0.928–0.992 P atom per formula unit). Concerning the other cations, the mineral shows a very restricted range of composition, without Fe and with very low Mn, Mg, Na and K contents. The indices of refraction are α = 1.530(2), β = 1.537(2) and γ (calculated for 2Vγ =86°) = 1.543. The measured density [Dm = 2.335(3)–2.342(5) g/cm3] agrees well with the calculated values [Dx = 2.317–2.350 g/cm3]. The average unit-cell parameters refined from 31 sets of X-ray powder diffraction data are a = 5.719(5), b = 31.012(28), c = 6.249(7)Å and β = 117.21(6)°. Thermally assisted X-ray diffraction analyses confirm that water is lost in three steps; the loss of molecular water is a two-step process and is complete below 250 °C. The first thermal breakdown products are brushite and bassanite. The band multiplicity on the IR-absorption spectrum (3v3+1v1+3v4+2v2) suggests that the protonated phosphate and sulfate groups have Cs point symmetry. The mineral derives from the reaction between calcium carbonate from the moonmilk flows or the cave floor and phosphoric solutions derived from bat guano, with or without hydroxylapatite as a precursor, at pH values up to 5.5.
Anna Vymazalová, František Laufek, Sergei F. Sluzhenikin, Chris J. Stanley, Vladimir V. Kozlov, Dmitry A. Chareev, Maria L. Lukashova
Published: 10 October 2017
European Journal of Mineralogy, Volume 29, pp 597-602; https://doi.org/10.1127/ejm/2017/0029-2653

Abstract:
Kravtsovite, PdAg2 S, is a new platinum-group mineral discovered in the Komsomolsky mine of the Talnakh deposit, Noril'sk district, Russia. It forms equant inclusions (ranging in size from a few μm to 40–50 μm) in silicates and pyrite, commonly intergrown with vysotskite and Au–Ag alloy in aggregates (100– 200 μm across) with telargpalite, cooperite, braggite, vysotskite, sopcheite, stibiopalladinite, sobolevskite, moncheite, kotulskite, malyshevite and insizwaite. Kravtsovite is brittle; it has a metallic lustre and a grey streak. In plane-polarised light, kravtsovite is yellowish white, has strong bireflectance, is strongly pleochroic in shades of slightly yellowish white to bluish grey, and exhibits a strong anisotropy with rotation tints of salmon-pink, orange, pale blue and dark blue – black. It exhibits no internal reflections. Reflectance values in air (R1, R2 in %) are: 32.2, 38.3 at 470, 31.6, 39.4 at 546, 30.2, 39.8 at 589 and 28.8, 41.1 at 650 nm. Eighteen electron probe microanalyses of kravtsovite give the average composition: Pd 30.53, Ag 60.11, S 8.47, and Se 0.74, total 99.85 wt%, corresponding to the empirical formula Pd1.03 Ag1.99 (S0.95 Se0.03)Σ0.98 based on a total of 4 atoms per formula unit (apfu). The average of eight analyses on synthetic kravtsovite is: Pd 30.98, Ag 60.27, and S 8.81, total 100.07 wt%, corresponding to Pd1.04 Ag1.99 S0.98. The mineral is orthorhombic, space group Cmcm, with a 7.9835(1), b 5.9265(1), c 5.7451(1) A, V 271.82(1) A3 and Z = 4. The crystal structure was refined from the powder X-ray-diffraction data of the synthetic analogue. The strongest lines in the X-ray powder diffraction pattern of synthetic kravtsovite [d in A (I) (hkl)] are: 2.632(51)(021), 2.458(65)(112), 2.4263(71)(310), 2.3305(60)(202), 2.2352(100)(311), 2.1973(48) (221), 2.0619(42)(022), 1.9172(30)(130), 1.3888(42)(240,332), 1.3586(28)(512). The mineral honours V. F. Kravtsov, one of the discoverers of the Talnakh and Oktyabrsk deposits in the Noril'sk district of Russia.
, , Chloé Loury, Marco Burn, Martin Engi
European Journal of Mineralogy, Volume 29, pp 181-199; https://doi.org/10.1127/ejm/2017/0029-2597

Abstract:
This contribution presents an approach and a computer program (GRTMOD) for numerical simulation of garnet evolution based on compositions of successive growth zones in natural samples. For each garnet growth stage, a new local effective bulk composition is optimized, allowing for resorption and/or fractionation of previously crystallized garnet. The successive minimizations are performed using the Nelder – Mead algorithm; a heuristic search method. An automated strategy including two optimization stages and one refinement stage is described and tested. This program is used to calculate pressure – temperature (P–T) conditions of crystal growth as archived in garnet from the Sesia Zone (Western Alps). The compositional variability of successive growth zones is characterized using standardized X-ray maps and the program XMapTools. The model suggests that Permian garnet cores crystallized under granulite-facies conditions at T>800°C and P = 6 kbar. During Alpine times, a first garnet rim grew at eclogite-facies conditions (650°C, 16 kbar) at the expense of the garnet core. A second rim was added at lower P (~1 kbar) and 630°C. In total, garnet resorption is modeled to amount to ~9 vol% during the Alpine evolution; this value is supported by our observations in X-ray compositional maps.
Faruk Aydin
Published: 7 March 2008
European Journal of Mineralogy, Volume 20, pp 101-118; https://doi.org/10.1127/0935-1221/2008/0020-1784

Abstract:
The Nigde volcanic province in central Turkey comprises four separate stratovolcanoes (Tepeköy, Cinarli, Melendiz and Keciboyduran) of Mio-Pliocene age (MPv) and several monogenetic cones of Pleistocene age (Pv). The MPv rocks are composed of large volume of andesitic lavas and pyroclastics with medium to high-K calc-alkaline character. They are strongly porphyritic with phenocryst assemblages of plag + opx + cpx + Fe-Ti oxides + bio ± amph ± quartz, and commonly exhibit disequilibrium textures such as complexly zoned plagioclases, reversely zoned pyroxenes, and reacted amphiboles and biotites. Geothermobarometric studies based on mineral chemistry data suggest that the MPv calc-alkaline magmas underwent a complex evolutionary history of cooling, crystallisation and mixing within two distinct magma chambers sited in the lower and in the upper crust, respectively. The rocks of Pv include small volumes of alkaline basalts showing poorly porphyritic textures and equilibrated phenocryst assemblages of ol + cpx + lesser plag and Fe-Ti oxides. Textural features, and strong compositional variations in single phenocrysts from andesites clearly reflect magma mixing-mingling and open-system modifications. Major and trace element evidence also argues against dominant fractional crystallisation processes and supports magma mixing for andesitic magmas. In contrast, textural, mineral chemical and geochemical evidence for Pv alkaline rocks indicate that magmas had a relatively simple evolutionary history dominated by small degrees of fractional crystallisation of mafic minerals along volcanic conduits. MPv show typical island-arc trace element signatures, such as negative anomalies in high-field strength element (HFSE) and high ratios between HFSE and large ion lithophile elements (LILE). Slight HFSE negative anomalies are also observed in Pliocene alkaline basalt, suggesting contamination by arc component, either in the source or during alkaline magma ascent.
Richard A.D. Pattrick, , C. Michael B. Henderson, Pieter Kuiper, Esther Dudzik, David J. Vaughan
Published: 25 November 2002
European Journal of Mineralogy, Volume 14, pp 1095-1102; https://doi.org/10.1127/0935-1221/2002/0014-1095

Abstract:
X-raymagnetic circular dichroism (XMCD) is an element-, site-and symmetry-selective spectroscopic technique that has the potential to provide quantitative information on site occupancies in ferri- and ferro-magnetic minerals. XMCD spectra derived from the Fe L2,3 absorption edge of a series of synthetic spinel ferrites and natural magnetite were collected using synchrotron radiation and a 0.6 Tesla 'flipper' magnet. These spectra were used to assess their potential value to mineralogical investigations. By comparison with theoretical spectra, the site occupancies of the cations have been calculated and compared to previous studies using other techniques. The spectra of the Co, Ni, Zn and Mg ferrite spinels show considerable variation, reflecting differences in site occupancies. Although the cation ratios derived from the XMCD spectra are broadly similar to previous work, there are significant differences especially in the amount of octahedral Fe2+ present. Incomplete inversion is recognised in all the spinels analysed and the affinity of Co, Ni and Mg for the octahedral site and Zn for the tetrahedral site is confirmed; the preference of Co over Ni for tetrahedral sites is also revealed. XMCD spectra proved relatively straightforward to analyse but further refinement of the quantitative calculations is needed and detailed comparison with the information derived from other methods, especially Mössbauer spectroscopy.
Published: 20 August 2018
European Journal of Mineralogy, Volume 30, pp 259-275; https://doi.org/10.1127/ejm/2017/0029-2677

Abstract:
Using combination of acid-solution, high-temperature oxide-melt, relaxation, and differential scanning calorimetry, we have determined the thermodynamic properties of all phases in the system Fe(SO44)(OH)–H2O (estimated values in parentheses): x in Fe(SO4)(OH)(H2O)x ΔfH° (kj·mol-1) S° ΔfG° (j·mol-1·K-1 log Ksp (kj·mol-1) Fe(SO4)(OH) 0 -1160.2 ± 2.3 145.9 ± 1.2 -1013.7 ± 2.4 -2.862 Metahohmannite 1.5 -1608.2 ± 1.7 (200.3) -1373.6 ± 1.8 -3.594 Butlerite 2 -1758.2 ± 1.7 (214.0) -1492.7 ± 1.8 -3.685 Parabutlerite 2 -1758.6 ± 1.7 214.0 ± 1.4 -1493.3 ± 1.8 -3.799 Amarantite 3 -2056.5 ± 1.8 243.8 ± 1.9 -1730.5 ± 1.9 -3.801 Hohmannite 3.5 -2197.8 ± 1.8 (271.4) -1845.3 ± 1.9 -3.138 Fibroferrite 5 -2641.5 ± 1.8 332.2 ± 2.7 -2202.8 ± 2.0 -3.456 Using these data, phase diagrams for low-temperature (25 °C) systems in contact with aqueous solutions predict that these phases should precipitate from extremely concentrated, low-pH solutions. In a relative humidity–temperature space, only Fe(SO4)(OH), parabutlerite, and amarantite have stability fields; the higher hydrates would require unrealistically high air humidities to form as stable phases. High-temperature high-pressure phase diagrams produce reasonable topologies, although the details of the phase relations between Fe(SO4)(OH), Fe2(SO4)3, and hydronium jarosite deserve more work. We also present a new structural model for amarantite, including the positions of the H atoms, and an analysis of the hydrogen bonding network in this mineral. Using the concept of information density in minerals, the Fe(SO4)(OH)(H2O)x phases were analyzed. This analysis lends some validity to the premise that more complex structures are also the more stable ones, but other systems should be investigated to test these trends.
Fredrik Sahlström, Kevin Blake, , Zhaoshan Chang
Published: 1 December 2017
European Journal of Mineralogy, Volume 29, pp 985-993; https://doi.org/10.1127/ejm/2017/0029-2660

Abstract:
Sphalerite is the most important host mineral for the recovery of indium. New techniques to study the presence and distribution of this critical metal in sphalerite can therefore be of interest for scientific and technological purposes alike. In this study we use the emerging tool of hyperspectral cathodoluminescence (CL) mapping, combined with X-ray element mapping and spot analyses, to characterise the composition and CL properties of indium-bearing sphalerite from the Mt Carlton high-sulphidation epithermal deposit (NE Queensland, Australia). Mt Carlton sphalerite contains highly elevated concentrations of indium (up to 19.57 wt%) occurring within ∼1 μm thick colloform bands, which show an average composition of (Zn0.63Cu0.20In0.15Ga0.01)S0.96. Indium, Cu and Ga are interpreted to have been incorporated via the coupled substitution 2Zn2+↔Cu++(In,Ga)3+. Hyperspectral CL mapping reveals a high-intensity CL emission directly related to In–Cu–(Ga)-rich sphalerite, centred at wavelengths between ∼500 and ∼600 nm. The CL peak is shifted to the higher-wavelength positions when the proportion of In relative to Cu increases. Our study shows that hyperspectral CL mapping is a powerful and efficient technique to study the distribution of In in sphalerite.
Teruyoshi Imaoka, , Takashi Kano, , Qing Chang, Chihiro Fukuda
Published: 1 December 2017
European Journal of Mineralogy, Volume 29, pp 1045-1053; https://doi.org/10.1127/ejm/2017/0029-2675

Abstract:
Murakamiite (IMA2016-066), ideally LiCa2Si3O8(OH), is a new mineral that was recently discovered in an aegirine-augite albitite exposed on the Iwagi Islet, Ehime Prefecture, Japan. It occurs as prismatic crystals and monomineralic aggregates up to 1.7mm long, is white to colourless with a white streak, and has a vitreous to silky lustre. It has a Mohs hardness of 4½–5 and is brittle with a splintery fracture and perfect {1 0 0} and {0 0 1} cleavage. Measured and calculated densities are Dmeas = 2.86(1) and Dcalc = 2.85(1) g·cm-3, respectively. Murakamiite is optically biaxial (+) and non-pleochroic, with refractive indices (in white light) of α = 1.602(1), β = 1.611(1), γ = 1.643(1), and with 2Vmeas=56–59(2)° and 2Vcalc=57°. Dispersion is weak, with r>v. The optical orientation is Xc 10–11°, Ya 10–14°, Zb 0–5°. Murakamiite is triclinic, belonging to space group P1- with the unit-cell parameters a = 7.9098(2)Å, b = 7.0320(2)Å, c = 6.9863(2)Å, α = 90.596(2)°, β = 95.589(2)°, γ = 102.767(2)°, V = 376.98(2)Å3 (Z = 2). The eight strongest lines in the X-ray powder diffraction pattern are [dobs/Å(I)(h k l)]: 2.897(100)(2 2- 0), 3.055(49)(0 1 2, 1 0 2, 1 1- 2-), 3.295(41) (1 0 2-), 3.225(33)(2 0 1), 3.845(20)(2 0 0), 2.284(19)(1 0 3-), 2.720(15)(1 2 1-, 2 2- 1, 2 0 2-), and 6.962(15)(0 0 1). The chemical composition is (average of sixteen analyses by LA–ICP–MS, H2O by TG–DTA, wt%): SiO2 54.94, Al2O3 0.01, FeO 0.38, MnO 0.80, MgO 0.04, CaO 34.14, Na2O 4.37, Li2O 2.52 and H2O 2.80. The empirical formula of murakamiite, based on 9 O apfu, is (Li0.55Na0.46)Σ1.01(Ca1.98Mn0.04Fe0.02)Σ2.04Si2.98O8(OH)1.01; thus, muakamiite is a H-bearing pyroxenoid with three-periodicity of SiO4 tetrahedra and the Li-analogue of pectolite. The species is named in honour of the late Professor Emeritus Nobuhide Murakami (1923–1994) of Yamaguchi University, Japan. Type specimens are housed in the National Museum of Nature and Science, Tsukuba, Japan, and the Geological and Mineralogical Museum of Faculty of Science, Yamaguchi University, Japan.
Andrew G. Christy
Published: 20 August 2018
European Journal of Mineralogy, Volume 30, pp 193-204; https://doi.org/10.1127/ejm/2017/0029-2674

Abstract:
The Goldschmidt classification of elements into “lithophile”, “chalcophile” and “siderophile” on the basis of geochemical preferences was devised to explain the distribution of elements through a differentiating planet, under conditions of high temperature, low bulk oxygen content and a range of pressures. Applying the concept to crustal materials is useful, if it is accepted that some elements classify very differently under low-temperature, high-oxygen conditions. A more nuanced, empirical ten-step scale of geochemical preferences has been constructed for educational use, as well as a thermochemically based quantification of preferences on the basis of two parameters which correspond respectively to “siderophile versus compound-forming” and “lithophile versus chalcophile”. Attempting to reconcile the empirical scale with the thermochemical one reveals several interesting discrepancies which nevertheless can be rationalised, and some predictive character for new types of compounds which should be sought as minerals. Overall, “lithophile” corresponds to “hard acid” in the sense of Pearson, “siderophile” corresponds to “electronegative and soft”, while “chalcophile” corresponds to “electropositive and soft”.
, Ann Cyphers, Maria De La Luz Rivas-Sánchez, , Judith Zurita-Noguera, Jaime Urrutia-Fucugauchi
Published: 15 December 2017
European Journal of Mineralogy, Volume 29, pp 851-860; https://doi.org/10.1127/ejm/2017/0029-2654

, Evgenii V. Nazarchuk, , Evgeniya A. Lukina, Evgeniya Y. Avdontseva, Lidiya P Vergasova, Natalia S. Vlasenko, Stanislav K. Filatov, Rick Turner, Gennady A. Karpov
Published: 12 July 2017
European Journal of Mineralogy, Volume 29, pp 499-510; https://doi.org/10.1127/ejm/2017/0029-2619

Márta Berkesi, Réka Káldos, , Csaba Szabó, Tamás Váczi, Kálmán Török, Bianca Németh, György Czuppon
Published: 12 July 2017
European Journal of Mineralogy, Volume 29, pp 423-431; https://doi.org/10.1127/ejm/2017/0029-2615

Ulf Hålenius, Frédéric Hatert, Marco Pasero, Stuart J. Mills
Published: 12 July 2017
European Journal of Mineralogy, Volume 29, pp 529-533; https://doi.org/10.1127/ejm/2017/0029-2662

, Luca Bindi, , , Joakim Mansfeld
Published: 1 December 2017
European Journal of Mineralogy, Volume 29, pp 1015-1026; https://doi.org/10.1127/ejm/2017/0029-2670

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, 100–300μm, in aggregates up to 2 mm. Fracture is uneven, and there is an indistinct cleavage parallel (0 0 1). Mohs’ hardness is 5–6, Dcalc = 4.97 g cm-3. Optically, ulfanderssonite-(Ce) is nonpleochroic, biaxial negative, with 2Vmeas=557deg; and ncalc = 1.82. The ideal composition is Ce15CaMg2(SiO4)10(SiO3OH)(OH,F)5Cl3. 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 (%) dobs (Å) (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)Å, β = 106.615(6)° and V = 2256.0(2)Å3 for Z = 2. The crystal structure has been solved by direct methods and refined to R1 = 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. 9Å thickness), with composition [(Ce8Ca)MgSi7O22(OH,F)4]8+, and B (ca. 6.5Å), with composition [Ce7MgSi4O21(OH,F)2Cl3]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 O–H 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.
, Gaëlle Plissart, Leonardo N. Garrido, , , , , Antonio Jesús Moreno-Abril, , , et al.
Published: 1 December 2017
European Journal of Mineralogy, Volume 29, pp 959-970; https://doi.org/10.1127/ejm/2017/0029-2668

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.
František Laufek, Anna Vymazalová, Tatiana Lvovna Grokhovskaya, , , Dmitryi Anatolevich Orsoev, Vladimir V Kozlov
Published: 10 October 2017
European Journal of Mineralogy, Volume 29, pp 603-612; https://doi.org/10.1127/ejm/2017/0029-2664

Abstract:
The crystal structure of sopcheite, Ag4Pd3Te4, has been solved using single-crystal diffraction data for a crystal from the Lukkulaisvaara intrusion, Karelia. The crystal structure is orthorhombic, space group Cmca, a = 12.212(2)Å, b = 6.138(2)Å, c = 12.234(3)Å, V = 917.1(4)Å3 and Z = 4. The refinement of the fully anisotropic model led to an R index of 6.47% for 413 unique reflections. Sopcheite crystallizes in a layered structure. The Pd(1) and Pd(2) atoms assume a nearly planar coordination by four Te atoms. Each of the [PdTe4] rectangles shares two opposite Te–Te edges with adjacent rectangles forming six-membered rings with the shape of elongated hexagons. These hexagons are oriented parallel to (1 0 0) and form layers of a herringbone pattern. Silver atoms form four-membered rings [Ag4] of almost square shape. The [Ag4] rings are located approximately in the centre of elongated hexagons composed of [PdTe4] rectangles. The crystal structure is stabilised by a number of metal–metal interactions. The crystal structure of the synthetic phase Ag4Pd3Te4 was also determined by single-crystal X-ray diffraction (XRD). It corresponds to the structure of sopcheite from the Lukkulaisvaara intrusion. Electron backscatter diffraction data obtained on material from other reported sopcheite occurrences are entirely consistent with this structure model, which is however incompatible with the sole powder XRD pattern reported so far for sopcheite. Combined with the absence of phase transition in Ag4Pd3Te4 up to its breakdown temperature, these results imply revision of the previously published crystallographic data of sopcheite.
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