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Ferrofettelite, ideally [Ag6As2S7][Ag10FeAs2S8], is a new mineral (IMA2021-094) from the Glasberg quarry, Nieder-Beerbach, Odenwald, south-western Germany. It occurs as anhedral to subhedral flakes and grains up to 80 μm, associated with proustite and xanthoconite, on arsenolite, calcite and prehnite. Ferrofettelite is opaque with a metallic lustre and possesses a dark reddish-grey streak. It is brittle with an uneven fracture; the Vickers microhardness (VHN20) is 122 kg/mm2 (range 111–131). The calculated density is 5.74 g/cm3 (on the basis of the empirical formula). In plane-polarised reflected light, ferrofettelite is greyish white. Between crossed polars it is weakly anisotropic with red internal reflections. Electron-microprobe analyses give the chemical formula Ag16.04(Fe0.55Hg0.40Cu0.02)Σ0.97(As3.94Sb0.03)Σ3.97S15.02 on the basis of total atoms = 36.Ferrofettelite is monoclinic, space group C2, with a = 26.011(2), b = 15.048(1), c = 15.513(1) Å, β = 90.40(1)° and V = 6071.9(7) Å3 for Z = 8. The six strongest Bragg peaks in the powder X-ray diffraction pattern (d, Å (I, %) (hkl) are: 3.18 (50) ($\bar{8}$01), 3.104 (100) (005), 3.004 (60) ($\bar{8}$02), 2.755 (40) ($\bar{4}$43), 2.501 (30) ($\bar{4}$44) and 1.880 (30) ($\overline {12}$40). The crystal structure can be described as the alternation of two kinds of layers along the c-axis: layer A with general composition [Ag6As2S7]2– and layer B with a general composition of [Ag10FeAs2S8]2+. In the structure, the Ag atoms adopt various coordinations extending from quasi linear to quasi tetrahedral, the AsS3 groups form pyramids as are typically observed in sulfosalts, and mixed (Fe,Hg) links two sulfur atoms in a linear coordination. Ferrofettelite is the first reported inorganic phase showing a linear coordination for Fe2+. The high-temperature behaviour of ferrofettelite was studied up to 410 K and compared to that of fettelite.

The crystal structure of a new high-pressure hydrous phase, Si-rich Mg-sursassite, of ideal composition Mg4Al5Si7O23(OH)5, that was produced by sub-solidus reaction at 24 GPa and 1400 °C in an experiment using a model sedimentary bulk composition, has been determined by single-crystal X-ray diffraction. The phase was found to be topologically identical to Mg-sursassite, Mg5Al5Si6O21(OH)7, and has space group P21/m and lattice parameters a = 8.4222(7), b = 5.5812(3), c = 9.4055(9) Å, b = 106.793(8)°, V = 423.26(6) Å3, and Z = 1. The empirical formula determined by electron microprobe analysis of the same crystal as was used in the X-ray experiment is [Mg3.93(3)Fe0.03(1)]Σ3.96[Al4.98(3)Cr0.04(1)]S5.02 Si7.02(4)O23(OH)5, with hydroxyl content implied by the crystal-structure analysis. The most significant aspect of the structure of Si-rich Mg-sursassite is the presence of octahedrally coordinated Si. Its structural formula is M1,VIIMg2M2,VIMg22+M3,VI(Al0.5Si0.5)2M4,VIAl2M5,VIAl2T1,IVSi2T2,IVSi2T3,IVSi2 O23(OH)5. Si-rich Mg-sursassite joins the group of hydrous ultrahigh-pressure phases with octahedrally coordinated Si that have been discovered by experiment, and that may play a significant role in the distribution and hosting of water in the deep mantle at subduction zones. The reactions defining the stability of Si-rich Mg-sursassite are unknown, but are likely to be fundamentally different from those of Mg-sursassite, and involve other ultrahigh-pressure dense structures such as phase D, rather than phase A.

The crystal structure and chemical composition of a crystal of Mg-bearing phase Egg with a general formula M1−x3+Mx2+SiO4H1+x (M3+ = Al, Cr; M2+ = Mg, Fe), where x = 0.35, produced by subsolidus reaction at 24 GPa and 1400 °C of components of subducted oceanic slabs (peridotite, basalt, and sediment), was analyzed by electron microprobe and single-crystal X-ray diffraction. Neglecting the enlarged unit cell and the consequent expansion of the coordination polyhedra (as expected for Mg substitution for Al), the compound was found to be topologically identical to phase Egg, AlSiO3OH, space group P21/n, with lattice parameters a = 7.2681(8), b = 4.3723(5), c = 7.1229(7) Å, β = 99.123(8)°, V = 223.49(4) Å3, and Z = 4. Bond-valence considerations lead to hypothesize the presence of hydroxyl groups only, thereby excluding the presence of the molecular water that would be present in the hypothetical end-member MgSiO3·H2O. We thus demonstrate that phase Egg, considered as one of the main players in the water cycle of the mantle, can incorporate large amounts of Mg in its structure and that there exists a solid solution with a new hypothetical MgSiH2O4 end-member, according to the substitution Al3+ ↔ Mg2+ + H+. The new hypothetical MgSiH2O4 end-member would be a polymorph of phase H, a leading candidate for delivering significant water into the deepest part of the lower mantle.

We report laser ablation inductively coupled plasma mass spectrometry measurements of the trace element contents of the two naturally occurring quasicrystalline minerals, Al63Cu24Fe13 icosahedrite and Al71Ni24Fe5 decagonite, from their type locality in the Khatyrka meteorite. The isolated quasicrystal fragments were mounted separately from any matrix and are larger than the laser beam diameter. When the elements are sorted in order of volatility, a systematic and unique pattern emerges in both bulk natural quasicrystal specimens. They are highly depleted compared to primitive solar system materials (chondritic meteorites) in moderately refractory elements (those with 50% condensation temperatures near 1350-1300 K; V, Co, Mg, Cr) and significantly enriched in moderately volatile elements (those with 50% condensation temperatures between 1250 and 500 K; Sb, B, Ag, Sn, Bi). We compare the chondrite-normalized trace element patterns and ratios of the quasicrystals to those of scoriaceous cosmic spherules and other meteoritic components. The nonmonotonic shapes of the chondrite-normalized trace element patterns in both icosahedrite and decagonite are incompatible with a single condensation process from the gas of the solar nebula. Previous transmission electron microscopy studies show that the natural quasicrystals contain 3-5 vol % of silicate and oxide nanoparticle inclusions, which we consider to be the main host of the measured trace elements. On this basis, we construct a three-stage model for the formation of the quasicrystals and their inclusions: a high-temperature condensation stage and a low-temperature vapor-fractionation stage to make nanoparticles, followed by a third stage that leads to the formation of quasicrystals incorporating the two different types of nanoparticles and their incorporation into the CV chondrite parent body of the Khatyrka meteorite.

Most geobarometers use chemical compositions of minerals and their host melt to estimate crystallization pressures. Crystal structural parameters such as cell and site volumes are not usually considered despite their known sensitivity to pressure. Here, we compare two clinopyroxene geobarometers based upon electron microprobe analysis alone and coupled with single-crystal X-ray diffraction data. The case study is the plumbing system of Popocatepetl volcano (Mexico), which consists of three distinct magma reservoirs in upper, middle and lower crustal depths, represented by three compositionally and texturally distinct clinopyroxene populations (T1, Mg# core 82, and low-Ca with a lower wollastonite component). These clinopyroxenes are augites of limited compositional variability, although yielding a significant increase in cell (V cell) and M1 site (V M1) volumes from low-Ca and T2 core clinopyroxenes to T1 (core and rim) and T2 (rim) clinopyroxenes. This variation is not due to chemical or temperature effects but is linked to their depth of crystallization. The application of the geobarometer based on chemical composition alone is unable to distinguish the three different reservoirs postulated on volcanological and petrological grounds. In contrast, the application of the geobarometer based on both structural parameters and chemical composition yields a remarkable correlation between the calculated cell volume and the estimated depth of crystallization of the different clinopyroxenes, including core to rim differences. These results have twofold implications. First, the determination of the structural parameters of clinopyroxenes is the only method to resolve the actual distribution of Mg, Fe2+, Fe3+ in the M1 and M2 structural sites and, given the sensitivity of cell and site volumes to pressure, permits to improve geobarometric estimates in volcanic plumbing systems. Second, the quantitative determination of the crystallization depth of the different clinopyroxenes has permitted to rescale the depth of the three different reservoirs in the plumbing system of the Popocatepetl Volcanic Complex located from ~30 km b.s.l. (low-Ca clinopyroxene) to ~18 km b.s.l. (T2 clinopyroxene core) and ~10-0 km b.s.l. (T1 clinopyroxene core and rim, T2 clinopyroxene rim) within the crustal structure of the Morelos platform. This provides further support to the complex plumbing system of the Popocatepetl Volcanic Complex consisting of polybaric storage layers of variable interconnected and interacting transient magma reservoirs.

Until 2009, the only known quasicrystals were synthetic, formed in the laboratory under highly controlled conditions. Conceivably, the only quasicrystals in the Milky Way, perhaps even in the Universe, were the ones fabricated by humans, or so it seemed. Then came the report that a quasicrystal with icosahedral symmetry had been discovered inside a rock recovered from a remote stream in far eastern Russia, and later that the rock proved to be an extraterrestrial, a piece of a rare CV3 carbonaceous chondrite meteorite (known as Khatyrka) that formed 4.5 billion years ago in the pre-solar nebula. At present, the only known examples of natural quasicrystals are from the Khatyrka meteorite. Does that mean that quasicrystals must be extremely rare in the Universe? In this speculative essay, we present several reasons why the answer might be no. In fact, quasicrystals may prove to be among the most ubiquitous minerals found in the Universe.

The crystal structure of the mineral montbrayite, a rare gold telluride, was solved using intensity data collected from a crystal of the co-type material from the Robb-Montbray mine, Montbray, Abitibi County, Québec, Canada. The study revealed that the structure is triclinic, space group P1, with cell parameters: a 10.8045(6), b 12.1470(6), c 13.4480(7) Å, ? 108.091(5), ? 104.362(5), ? 97.471(5)8, and V 1583.65(15) Å3. The refinement of an anisotropic model led to an R index of 6.36% for 5145 independent reflections with Fo < 4?(Fo), GooF 1.023. There are 19 Te sites and 12 Au sites in the crystal structure of montbrayite. The Au sites host variable amounts of Sb, whereas all the Te sites but one host only Te. All the Au atoms can be considered to be in octahedral coordination forming more regular AuTe6 or more distorted AuTe4+2 polyhedra, with the exception of one Au position which links five Te atoms and closes its coordination sphere with a contact with itself. Crystalchemical features of the Au and Te atoms are discussed in relation to other gold and silver tellurides. Electron microprobe analyses of the crystal used for the structural study led to the formula Au21.60Sb0.68Te37.41Bi1.31, calculated on the basis of 61 atoms per formula unit. On the basis of information gained from the structural and chemical characterization, the crystalchemical formula was revised, yielding (Au,Ag,Sb,Bi,Pb)23(Te,Sb,Bi,Pb)38 (Z = 1) instead of (Au,Sb)2Te3 (Z = 12) as previously reported. The redefinition of montbrayite has been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (voting proposal 17-F). © 2018 Mineralogical Association of Canada. All rights reserved.

The paper starts from critical animal studies and animal rights debate but also focuses on new roles for ethnographers in the field as mediators and engaged researchers. This introduces a case-study of a group of ceremonials involving animals in the South of Italy (Molise), recently accused of abuses by animal rights movements. The aroused legal dispute was solved through a mediation process in which anthropologists and vets were engaged as experts working with local communities and their legal representatives. A new set of rules was, then, established coherently with national codes for animal welfare.

Jaszczakite, [(Bi,Pb) 3 S 3 ][AuS 2 ], represents another new species from the abandoned Nagyborzsony Au deposit at Also-Rozsa, northern Hungary. The mineral is closely associated with arsenopyrite, pyrite, marcasite, sphalerite, chalcopyrite, gold, bismuth, bismuthinite, ikunolite, jonassonite, and cosalite, in a matrix of quartz. It is opaque, tin-white, has a metallic lustre and a black streak. Jaszczakite is brittle, and the fracture is irregular. Neither cleavage nor parting are observable in the section. The VHN 5 value ranges between 115 and 132 (mean 122) kg mm −2 which corresponds to a Mohs hardness of 2½–3. The calculated density is 7.327 g cm −3 . In plane-polarized light jaszczakite is weakly bireflectant and pleochroic from light grey to a slightly bluish grey. Internal reflections are absent. The mineral is distinctly anisotropic with rotation tints very similar to those of jonassonite (shades of green and purple). The reflectance COM values (air, R 1 and R 2 in %) are: 49.4, 50.9 (471.1 nm); 47.1, 48.8 (548.3 nm); 46.5, 47.7 (586.6 nm); 48.8, 49.5 (652.3 nm). The average result of five electron-microprobe analyses is Au 19.90(34), Ag 0.22(3), Bi 46.29(54), Pb 16.50(26), Cd 0.11(3), Sb 0.12(4), As 0.08(3), S 16.17(30), Se 0.16(6), total 99.55 wt%. The empirical formula (based on 9 atoms pfu ) is Au 1.00 Ag 0.02 Bi 2.18 Pb 0.78 Cd 0.01 Sb 0.01 As 0.01 S 4.97 Se 0.02 or, according to the refinement results, [(Bi 2.18 Pb 0.78 Ag 0.02 Cd 0.01 Sb 0.01 As 0.01 ) Σ=3.01 S 3 ][AuS 2 ]. The simplified formula is AuBi 3 S 5 , which requires Au 20.01, Bi 63.70, S 16.29, total 100.00 wt%. Jaszczakite is orthorhombic, space group Pmmn , with unit-cell parameters: a = 3.858(1), b = 12.552(3), c = 9.289(2) A, V = 449.83(8) A 3 , a : b : c = 0.3074:1:0.7400, Z = 2. The five strongest observed X-ray powder-diffraction lines [ d in A ( I / I 0 ) ( hkl )] are: 7.466 (100) (011), 6.2760 (90) (020), 5.2003 (24) (021), 3.0963 (68) (003), 2.7768 (26) (023). The crystal structure showed that jaszczakite is the S–Bi-analogue of buckhornite [Pb 2 BiS 3 ][AuTe 2 ]. Jaszczakite is named in honour of John A. Jaszczak, Professor of Physics at the Michigan Technological University, for his significant contributions on the complexities of natural graphite.