The crystal structure of averievite, Cu5O2(VO4)2·nMX has been determined. Trigonal system, space group P3, a = 6.375(1), c = 8.399(1) Å, V = 295.6(1) Å3, Z = 1, Dx = 4.01(1) g/cm3. The atomic arrangement is characterized by infinite nets parallel to (001) composed of [OCu4]6+ tetrahedra linked via corners in hexagonal rings. The bases of neigbouring tetrahedra are in one plane and their non-shared corners are turned to the opposite sides. The [VO4]3− tetrahedra are attached to the bases of [OCu4] tetrahedra. There are large (R >3.2 Å) channels in the structure where large molecular particles can enter. The comparison of the averievite structure with related compounds (in particular, copper oxovanadates) is given from the point of view of [OT4] polyion crystal chemistry.

A new mineral, nukundamite, from a Fijian kuroko deposit is described. It has been referred to as idaite, Cu5FeS6, or Cu5.5xFexS6.5x. Electron-probe analyses gave Cu 56.51, Fe 9.64, and S 33.51, total with traces of Ag and As is 99.79%. Hexagonal with a 3.782, c 11.187 Å, Z = 1. Empirical formula Cu3.37, Fe0.66, S3.97 on the basis of eight atoms. Copper-coloured, metallic lustre, cleavage {0001} perfect. Density (g cm−3) 4.53 (calc), 4.30 (meas). Strongly pleochroic from reddish orange (Ro) to pale grey (Re). Parallel extinction. Very strong anisotropy with pale green-grey rotation colours. Reflectance values and quantitative colour values in air and oil are given. Similarities with the covelline structure are indicated.

An attempt to fully describe idaite from the Ida mine was unsuccessful. The description of the type material therefore remains inadequate.

The Huanglongpu carbonatites are located in the north-western part of the Qinling orogenic belt in central China. Calcite carbonatite dykes at the Dashigou open pit are unusual due to their enrichment in heavy rare earth elements (HREE) relative to light rare earth elements (LREE), leading to a flat REE pattern, and in that the majority of dykes have a quartz core. They also host economic concentrations of molybdenite. The calcite carbonatite dykes show two styles of mineralogy according to the degree of hydrothermal reworking, and these are reflected in REE distribution and concentration. The REE in the little-altered calcite carbonatite occur mostly in magmatic REE minerals, mainly monazite-(Ce), and typically have ΣLREE/(HREE+Y) ratios from 9.9 to 17. In hydrothermally altered calcite carbonatites, magmatic monazite-(Ce) is partially replaced to fully replaced by HREE-enriched secondary phases and the rocks have ΣLREE/(HREE+Y) ratios from 1.1 to 3.8. The fluid responsible for hydrothermal REE redistribution is preserved in fluid inclusions in the quartz lenses. The bulk of the quartz lacks fluid inclusions but is cut by two later hydrothermal quartz generations, both containing sulfate-rich fluid inclusions with sulfate typically present as multiple trapped solids, as well as in solution. The estimated total sulfate content of fluid inclusions ranges from 6 to >33 wt.% K2SO4 equivalent. We interpret these heterogeneous fluid inclusions to be the result of reaction of sulfate-rich fluids with the calcite carbonatite dykes. The final HREE enrichment is due to a combination of factors: (1) the progressive HREE enrichment of later magmatic calcite created a HREE-enriched source; (2) REE–SO42– complexing allowed the REE to be redistributed without fractionation; and (3) secondary REE mineralisation was dominated by minerals such as HREE-enriched fluorocarbonates, xenotime-(Y) and churchite-(Y) whose crystal structures tends to favour HREE.

Weakly peralkaline syenite ejecta within the plinian fall deposits of Agua de Pau volcano (São Miguel, Azores Islands) are divisible into (1) silica-undersaturated and (2) silica-saturated/oversaturated groups. The first group occurs in the pre-Fogo-A pyroclastic falls (15.2 ka) whereas the second occurs in the Fogo-A pumices (5 ka). The petrography indicates that the syenites of both groups crystallized at shallow depths and whole-rock geochemistry shows that they have compositions reflecting those of the Agua de Pau trachyte magmas. The syenites are inferred to be derived from solidification zones around the margins of the parental magma chamber. Mineral parageneses in both syenite groups permit distinction of three magmatic stages of crystallization: (1) an early crystallization stage; (2) a main crystallization stage during which most of the feldspar growth occurred; and (3) a late interstitial stage. Crystallization of the trachytic magmas yielded peralkaline residuals, highly enriched in volatiles, alkalis, HFSE and REE. In the silica-undersaturated syenites, the complex Zr-Ti silicate minerals, eudialyte and a låvenite-like mineral, crystallized interstitially from the residual magmas. In contrast, the zircono-silicate dalyite, and REE-rich minerals (chevkinite-(Ce), britholite-(Ce) and pyrochlore), together with thorite, were late-stage interstitial products of the silica-saturated/oversaturated syenites.

Geochemical processes and mineralogical transformations in the spontaneously combusting coal waste pile of the Kukla mine in Oslavany, Czech Republic, were investigated. The aims of the study were: (1) the characterization of secondary minerals; and (2) determination of processes which influence the mobility of elements in the pile. The pile burned from the late 19th century until the 1990s and has acquired a zoned nature, with original black material in the core of the pile, red material produced by burning close to the pile slopes and grey and white efflorescent salts precipitated on the pile top and slopes. Several mineral assemblages have been identified including (1) primary minerals in the black material including bituminous coal to anthracite, micas, pyrite and goethite; (2) hematite, spinels and corundum in the red materialproduced by pyrometamorphism; and (3) hydrated sulphates of magnesium including hexahydrite, konyaite and picromerite in efflorescent precipitates on the slopes of the pile. A conceptual model of geochemical processes in the pile includes seasonal changes with mineral dissolution during the wet season and precipitation of efflorescent salt minerals during the dry season. Formation of secondary minerals such as hematite, which is resistant to weathering and immobilizes hydrolysable Fe, may have a positive environmental impact in the long term.

The early P-T evolution of a garnet-kyanite gneiss from the Variscan Ulten Zone has been defined by detailed petrographic observations leading to the detection of chlorite-epidote- and staurolite-bearing assemblages enclosed in kyanite porphyroblasts. Calculations of P-T pseudosections in the system NaCaKFeMgAlSiHO allowed us to constrain the evolution of these relics to the earliest metamorphic stages. The overall path shows a P-T increase to a peak of 11–12 kbar and 600–650°C followed by decompressional heating to 720°C and 9–10 kbar and final cooling at 7 kbar, 550–600°C. This clockwise P-T path reflects crustal thickening and subsequent thermal decay related to the continental collision of the Variscan orogeny 330–340 Ma ago. Our study demonstrates that large kyanite porphyroblasts may preserve assemblages related to prograde metamorphic stages. As a result, the detection of mineral inclusions in kyanite can complement many similar studies on mineral suites hosted in garnet and zircon.

The Grønnedal-Íka ring complex (1299 ± 17 Ma) in the Gardar province, South Greenland is composed of a range of layered nepheline syenites which were intruded at a late stage by xenolithic syenite and a plug of carbonatite. The complex was subsequently intruded by a variety of basic dykes, including olivine dolerites, kersantites, vogesites, spessartites, camptonites and an alnöite, and then extensively faulted. The nepheline syenite magmas, produced by fractional crystallisation of basic magmas, show a range in δ13C (−3.86 to −7.57‰) and δ18O (8.27 to 15.12‰), distinctly different to the carbonatites which form a tight group with average δ13C = −4.31 + 0.22 ‰, (1 s.d.) and average δ18O = 7.18 ± 0.41‰ (1 s.d.). Initial 87Sr/86Sr isotope ratios (typically 0.703) suggest the syenites and carbonatites have not assimilated crustal rocks, and therefore the C and O isotope variation within each group is a result of isotopic evolution during fractional crystallisation. A suite of lamprophyre dykes (δ13C −3.86 to −7.86‰ and δ18O 9.12 to 10.81‰) form a coherent group whose stable isotope compositions overlap part of the syenite field, and again are distinctly different from the carbonatites. A single alnöite has δ13C = −3.32‰ and δ18O = 12.34‰ C and O isotope ratios are consistent with origins of syenitic and lamprophyric magmas from a similar source. Despite geochemical evidence which suggests a genetic link between nepheline syenites and carbonatites, C and O isotopic evidence shows that they are not related directly by liquid immiscibility. Comparisons are made between similar rock types from Grønnedal-Íka and from the Gardar Igaliko Dyke Swarm. The possible role of F in controlling δ13C and δ18O during crystallisation of calcite from carbonatite magmas is discussed.

The line connecting rare earth elements (REE) in chondrite-normalised plots can be represented by a smooth polynomial function using λ shape coefficients as described by O'Neill (2016). In this study, computationally generated λ combinations are used to construct artificial chondrite-normalised REE patterns that encompass most REE patterns likely to occur in natural materials. The dominant REE per pattern is identified, which would lead to its inclusion in a hypothetical mineral suffix, had this mineral contained essential REE. Furthermore, negative Ce and Y anomalies, common in natural minerals, are considered in the modelled REE patterns to investigate the effect of their exclusion on the relative abundance of the remainder REE. The dominant REE in a mineral results from distinct pattern shapes requiring specific fractionation processes, thus providing information on its genesis. Minerals dominated by heavy lanthanides are rare or non-existent, even though the present analysis shows that REE patterns dominated by Gd, Dy, Er and Yb are geologically plausible. This discrepancy is caused by the inclusion of Y, which dominates heavy REE budgets, in mineral name suffixes. The focus on Y obscures heavy lanthanide mineral diversity and can lead to various fractionation processes to be overlooked. Samarium dominant minerals are known, even though deemed unlikely by the computational model, suggesting additional fractionation processes that are not well described by λ shape coefficients. Positive Eu anomalies only need to be moderate in minerals depleted in the light REE for Eu to be the dominant REE, thus identifying candidate rocks in which the first Eu dominant mineral might be found. Here, I present an online tool, called ALambdaR that allows interactive control of λ shape coefficients and visualisation of resulting REE patterns.

The Kabwe Zn-Pb deposit (central Zambia) consists of a cluster of mixed sulfide and non-sulfide orebodies. The sulfide ores comprise sphalerite, galena, pyrite, chalcopyrite and accessory Ge-sulfides (±Ga and In). The non-sulfide ores comprise: (1) willemite-dominated zones encasing massive sulfide orebodies and (2) oxide-dominated alteration bands, overlying both the sulfide and Zn-silicate orebodies. This study focuses on the Ge, In and Ga distribution in the non-sulfide mineralization, and was carried out on a suite of Kabwe specimens, housed in the Natural History Museum Ore Collection (London). Petrography confirmed that the original sulfides were overprinted by at least two contrasting oxidation stages dominated by the formation of willemite (W1 and W2), and a further event characterized by weathering-related processes. Oxygen isotopic analyses have shown that W1 and W2 are unrelated genetically and furthermore not related to supergene Zn-Pb-carbonates in the oxide-dominated assemblage. The δ18O composition of 13.9–15.7‰ V-SMOW strongly supports a hydrothermal origin for W1. The δ18O composition of W2 (−3.5‰ to 0‰ V-SMOW) indicates that it precipitated from groundwaters of meteoric origin in either a supergene or a low-T hydrothermal environment. Gallium and Ge show a diversity of distribution among the range of Zn-bearing minerals. Gallium has been detected at the ppm level in W1, sphalerite, goethite and hematite. Germanium occurs at ppm levels in W1 and W2, and in scarcely detectable amounts in hemimorphite, goethite and hematite. Indium has low concentrations in goethite and hematite. These different deportments among the various phases are probably due to the different initial Ga, In and Ge abundances in the mineralization, to the different solubilities of the three elements at different temperatures and pH values, and finally to their variable affinities with the various minerals formed.

The petrography of the Mount Padbury meteorite, previously briefly recorded, is described in some detail. Both the metalliferous host material of the mesosiderite and the varied range of silicate-rich, virtually metal-free enclaves (including both familiar achondrite material and unfamiliar achondrite material) are described. Eucrite, brecciated eucrite, and a peculiar ‘shocked’ form of eucrite (resembling some terrestrial flaser-gabbros) are the calcium-rich achondrite types represented; hypersthene achondrite (including typical diogenite material and unfamiliar material) and olivine achondrite (granular aggregates of olivine not entirely similar to the unique chassignite and single crystals up to 4 in. in length) are the calcium-poor achondrite types represented. The eucrite displays more or less uniform mineralogy, but the mineral constituents are present in varying proportions, and there is a wide range of textural variations recognized. The silicate grain fragments enclosed in the metallic reticulation to form the mesosiderite host material are, significantly, entirely of minerals seen within the achondrite enclaves—plagioclase, hypersthene, pigeonite, olivine, and tridymite.

These results include microscopic analysis of thin sections and polished sections, X-ray diffraction studies, optical determination of refractive indices using mineral grain mounts, and chemical analyses.

The wider implications of this new and unique meteorite find are briefly considered.

The association of orthoclase and microcline in the same rock has been commented on by many writers, and from these occurrences attempts have been made to deduce the relative stability of these two low-temperature forms of potash-felspar. Ahnost all investigators have concluded that nlicrocline is the lower-temperature modification, but difficulties in explaining the relationship of adutaria to orthoclase and microcline have been encountered.

The identification of the monoclinie potash-felspar in association with microcline is almost always based on optical properties, viz. straight extinction in the zone [010] or the absence of visible multiple twinning.

The North Qôroq syenite centre forms part of the Gardar Province of South Greenland. Extensive metasomatism, associated with the evolution of syenitic magmas, has resulted in redistribution of the rare-earth elements (REE), originally concentrated by magmatic processes, in both the syenites and surrounding granite-gneiss and quartzite country rocks. An important host for REE is apatite which can occur in significant quantities. Metasomatic apatites show complex, concentric, but irregular patterns of zonation, clearly seen using CL and BSE imaging. This zonation is related to successive pulses of metasomatising fluids. Electron microprobe analysis confirms the presence of significant quantities of REE in the apatites. The dominant cation exchange mechanism proposed is Ca2+ + P5+ ⇌ REE3+ + Si4+. In contrast to apatites from the nearby Ilímaussaq intrusion, there is no significant Na present in the structure and exchange reactions involving Na+ and REE3+ for Ca2+ have not occurred.

Apatites from the quartzite are fluor-apatites, while those from the granite-gneiss are more Cl-rich. These differences reflect the fact that granite-gneiss apatites are original and modified by metasomatism, whereas, those in the quartzite are metasomatic in origin. REE were probably transported as carbonate, fluoride or fluor-carbonate complexes, and reflect the activity of a F−-rich, CO2−3-rich fluid phase.

Critical raw materials (CRMs) are crucial for the transformation towards low carbon mobility. However, their production is often highly concentrated in a few countries, which leads to supply risks. Exemplified by the case of rare earth elements (REEs) and based on in-depth interviews with corporate executives from companies along the automotive supply chain, this contribution provides insights into the strategies of the European automotive industry to cope with these supply risks. Results show a lack of awareness of REE criticality studies and their outcomes in the past, the decisive role of price competitiveness when pursuing mitigation strategies and a lack of willingness or ability to engage in rare earth (RE) projects to get access to production output and secure supply. Overall, affected companies struggle to pursue long-term oriented strategies to secure their need for REEs. These findings are discussed with regard to the new demand for CRMs due to the shift to electric mobility and the specific challenges that the automotive industry faces.

Reyerite from the original locality in Greenland has been re-examined using chemical analysis, infra-red absorption, X-ray powder and single-crystal diffraction, and thermal weight-loss curves. The unit cell is trigonal with a 9·74, c 19·04 Å, and the space group is probably P3¯. The unit cell contents are probably best represented as KCa14(Si24O60)(OH)5.5H2O, with some minor replacements. The molecular water is lost reversibly below 400° C. There are indications that the crystal structure is based on Si6O18 rings resembling those in beryl, but linked into sheets by additional tetrahedra.

Reyerite closely resembles truscottite, a mineral found originally in Sumatra, but there are distinct differences, especially in the infra-red pattern. It is not yet certain whether or not the two minerals should be considered as distinct species. Synthetic preparations examined resembled truscottite more closely than reyerite.

Liquids in the system CaO-Na2O-MgO-Al2O3-SiO2 which crystallize plagioclase and forsterite, often with diopside and sometimes with spinel, were studied. The movement of the plagioclase-forsterite saturation surface to higher plagioclase contents as albite replaces anorthite, and the concurrent expansion of the forsterite and diopside primary fields, are documented. The maximum temperature of the liquid in equilibrium with plagioclase, diopside, and forsterite decreases as the anorthite to albite ratio decreases and as enstatite is added, and was experimentally determined over part of its range from 1278 to 113°C The decrease was not linear, being generally small even when 67 mole% albite was present, and thereafter, it must decrease rapidly to reach the values reported for the system albite-diopside-forsterite.

Two kinds of vitreous material with composition K2GeSi3O9 and K2Si4O9 were treated under conditions of high temperature and pressure. The X-ray diffraction patterns of the products were similar to that of K2TiSi3O9, which has the wadeite, K2ZrSi3O9, structure.

A natural crystal of K-feldspar was also treated under the same conditions. The product was found to consist of three phases, coesite, kyanite, and the above-mentioned K2Si4O9. Since Zr ions in wadeite are in a 6-coordinated site, one-quarter of Si ions in K2Si4O9 are considered to be in 6-coordination. This is the first silicate in which Si ions occupy sites of 4- and 6-coordinations in one crystal at the same time.

The crystal structure of mereheadite (monoclinic, Cm, a = 17.372(1), b = 27.9419(19), c = 10.6661(6) Å, β = 93.152(5)°, V = 5169.6(5) Å3) has been solved by direct methods and refined to R1 = 0.058 for 6279 unique observed reflections. The structure consists of alternating Pb–O/OH blocks and Pb–Cl sheets oriented parallel toth e (201) plane and belongs toth e 1:1 type of lead oxide halides with PbO blocks. It contains 30 symmetrically independent Pb positions, 28 of which belong to the PbO blocks, whilst two positions (Pb12 and Pb16) are located within the tetragonal sheets of the Cl– anions. Mereheadite is thus the first naturally occurring lead oxychloride mineral with inter-layer Pb ions. The coordination configurations of the Pb atoms of the PbO blocks are distorted versions of the square antiprism. In one half of the coordination hemisphere, they are coordinated by hard O2– and OH– anions whose number varies from three to four, whereas the other coordination hemisphere invariably consists of four soft Cl– anions located at the vertices of a distorted square. The Pb12 and Pb16 atoms in between the PbO blocks have an almost planar square coordination of four Cl– anions. These PbCl4 squares are complemented by triangular TO3 groups (T = B, C) so that a sevenfold coordination is achieved. The Pb–O/OH block in mereheadite can be obtained from the ideal PbO block by the following list of procedures: (1) removal of some PbO4 groups that results in the formation of square-shaped vacancies; (2) insertion of TO3 groups into these vacancies; (3) removal of some Pb atoms (that correspond to the Pb1A and Pb2A sites), thus transforming coordination of associated O sites from tetrahedral OPb4 tot riangular OHPb3; and (4) replacement of two O2– anions by one OH– anion with twofold coordination; this results in formation of the 1×2 elongated rectangular vacancy. The structural formula that can be derived on the basis of the results of single-crystal structure determination is Pb47O24(OH)13Cl25(BO3)2(CO3). Welch et al. (1998) proposed the formula Pb2O(OH)Cl for mereheadite, which assumes that neither borate nor carbonate is an essential constituent of mereheadite and their presence in the mineral is due to disordered replacements of Cl– anions. However, our study demonstrates that this is not the case, as BO3 and CO3 groups have well-defined structural positions confined in the vacancies of the Pb–O/OH blocks and are therefore essential constituents. Our results also show that mereheadite is not a polymorph of blixite, but is in fact related to symesite. Symesite thus becomes the baseline member of a group of structurallyrelated minerals.

Nifontovite and olshanskyite, two rare hydrous calcium borate minerals, have been found in crystalline limestone near gehlenite-spurrite skarns at Fuka, Okayama Prefecture. Nifontovite occurs as aggregates of tabular crystals up to 5 cm long and 1.5 cm wide, and rarely as euhedral crystals up to 1 mm long. Olshanskyite occurs as anhedral masses, or as micro-twinned platy crystals up to 1 cm long. Wet chemical analyses give the empirical formulae Ca3.052B5.991O6.038(OH)12·1.96H2O and Ca2.888B3.997(OH)18 on the basis of O = 20 for nifontovite and OH=18 for olshanskyite, respectively. The formulae are consistent with those from type localities.

The X-ray powder data for these minerals were determined with accuracy. The unit cell parameters of nifontovite agree closely with those published previously. X-ray studies show that olshanskyite is triclinic with the possible space group P1̄ or P1 and a = 9.991(5), b = 14.740(11), c = 7.975(3) Å, α = 94.53(4), β = 69.08(3), γ = 112.44(5)° and Z = 3. The density 2.19 g cm−3 (meas.) obtained for olshanskyite agrees with the estimated ideal value 2.31 g cm−3 (calc.). Nifontovite was formed by hydrothermal alteration of an anhydrous borate, and olshanskyite was formed by hydrothermal alteration of nifontovite and the anhydrous borate.

Within the Alston Orefield of the North Pennines, glaucodot and gersdorffite have been found in samples from Tynebottom Mine, Garrigill, and zoned gersdorffite has been found from Nenthead and the Great Sulphur Vein. At Scar Crag in the English Lake District, glaucodot and alloclase (the first reported occurrence in the United Kingdom) occur associated with arsenopyrite and minor cobaltite and skutterudite. The mineralogy and parageneses of these associations have been studied by ore microscopy, X-ray powder photography, and electron probe microanalysis.

Electron probe microanalysis shows a considerable range in nickel content in the sulpharsenides from the Alston Orefield with a relatively constant Co:Fe ratio. Samples from Scar Crag contain no nickel but exhibit almost a complete range of Co:Fe ratios from FeAsS to CoAsS. The compositions of the Alston Orefield sulpharsenides, in particular, show them to be metastable phases when compared with data from synthetic studies. At Tynebottom Mine, glaucodot and gersdorffite overgrow arsenical marcasite, and at Nenthead and the Great Sulphur Vein, early pyrite framboids or euhedra act as cores to zoned gersdorffite crystals. The Scar Crag sulpharsenides occur in a quartz chlorite apatite vein with the glaucodot and alloclase as overgrowths on arsenopyrite.

In the case of the Scar Crag association, consideration of the compositions of coexisting phases, together with precise determinations of the arsenic content of the arsenopyrites, has permitted speculation regarding temperatures and sulphur activities during ore formation. Estimated ranges are Tc. 400 °C–300 °C and aS2 ≈ 10−9–10−11 11 bar. The occurrence of the sulpharsenides in the Alston Orefield correlates with further geochemical differences compared to other Pennine ores, differences that have been linked to higher temperatures of formation and a magmatic contribution to the ore-forming fluid. The Scar Crag mineralization may be related to a postulated stock intrusion beneath Causey Pike and the geographical proximity of the Alston and Scar Crag occurrences does suggest the possibility of a genetic link.