Water in the form of hydrous-point-defect pyroxenes from mantle xenoliths is used to trace the water content in the lithospheric mantle. However, little is known about the mechanism that allows xenoliths to preserve deep hydrogen signatures. In particular, it is unknown how much of the water content of xenoliths is modified during the emplacement of lava and cooling at the surface and by the eruption mode (effusive versus explosive). In this work, we attempted to address these matters.

By applying in situ high-temperature Raman spectroscopy to (OH)^-- and Fe²⁺-bearing fluorophlogopite we show that a phonon-driven structural instability near 600 K triggers the mobilization of interlayer K⁺ cations, which can act as charge carriers. Above 1100 K all H⁺ cations delocalize and can also contribute to transport processes. Above 1300 K oxidation of Fe takes place, along with limited dehydrogenation and dehydroxylation, facilitating partial K⁺ leakage and structural decomposition.

Researchers studying the Bayan Obo deposit in northern China discovered an unknown mineral named xianhuaite-(Ce). The mineral contains the elements potassium, cerium, and niobium. Using microscopes, chemical analyses, and X-ray measurements, the researchers determined its structure and properties. The study shows that this mineral records the formation of rare earth and niobium ores in geological processes, improving our understanding of how these important resources formed.

The Ihalainen deposit in Finland produces wollastonite, a silicate of calcium. It formed 1.86 x 10⁹ years ago; 240 x 10⁶ years later, the area was invaded by a fluorine-rich granitic magma, which interacted with the marble host. The silicate magma lost silica and alkalis; the marble melted. A fluorine-rich vapor phase mobilized niobium, tantalum, and tin to form unknown minerals. The fluid was initially CO₂-dominant and then became aqueous and formed a complex assemblage of alteration minerals.

The paper describes bainbridgeite-(NdCe), Na₂Ba₂NdCe(CO₃)₆∙3H₂O, from the famous Mont Saint-Hilaire complex, Quebec, Canada, the first known mineral with Ce and Nd atoms preferentially concentrated at two different sites of the structure

We investigate how trace elements are incorporated into quartz formed in magmatic–hydrothermal ore deposits, key environments for critical metal enrichment. By tracking Li, B, Al, Ti, and OH defects across crystal growth zones we reveal distinct trace element zonation patterns linked to temperature and pressure evolution during crystallization. We demonstrate that combined trace element data and mapping of quartz can be a powerful tool for understanding ore deposit genesis and prospecting ores.

Boron and its isotopes, ¹¹B and ¹⁰B, can track magmatic–hydrothermal processes, but this requires knowing how the isotopes fractionate between melt and fluid, which depends on B coordination. This is known for aqueous fluids but not for silicate melts. We determined B coordination by nuclear magnetic resonance in granitic glass with variable water content and alkali–alumina ratios. The results provide a way to estimate B coordination and melt–fluid fractionation for variable melt compositions.

Yttrotungstite-(Nd) is a new mineral species discovered in the Nyakabingo tungsten mine, Kigali, Rwanda. The mineral occurs in the oxidized zones of the deposit, where it forms tiny yellow-orange tabular crystals that reach a length of maximum of 100 µm, and frequently form radiated groups. The dominant form is {010}, and a twinning has been observed parallel to (001). Electron microprobe analyses and structural data, confirming that the species belongs to the yttrotungstite group.

Deposits of bat guano in cave environments host diverse assemblages of secondary minerals, which can go through partial dehydration processes in response to varying environmental conditions. In this article, we investigate the thermodynamics and kinetics which lead guano-derived taranakite to lose part of its structural water and transform into francoanellite. Our results allow us to present evidence-based hypotheses to explain the occurrence of the latter in natural environments.

The paper is on the new mineral species piilonenite-(Nd), a new Nd-dominate carbonate with no closely related minerals or synthetic compounds from Mont Saint-Hillarie, Canada.

Argentotennantite-(Fe), ideally Ag₆(Cu₄Fe₂)As₄S₁₃, is a new member of the tetrahedrite group found in the San Genaro mine, Castrovirreyna Province, Huancavelica, Peru. It occurs as anhedral grains up to 100 μm in size, or, more commonly, it forms micrometer-sized rims around crystals of argentotetrahedrite-(Zn) or replaces the latter around cavities and fissures, along with Ag-rich tennantite-(Fe). It is cubic, I3m, with a = 10.4365(5) Å, V = 1136.75(17) ų.

Black opal, a rare amorphous SiO₂ variety, results from the interaction of silica with organic matter and therefore hints at traces of life, including the early Earth and Mars. The Volyn occurrence is one of the few examples of black opal worldwide and is the unique case of a pegmatitic occurrence in a granite; its age is at least 200 Ma. The structure consists of micrometer-large sphere-like arrangements of nano-sized grains and shows shape relicts of fossils, known from Volyn as "kerite".

Mineralogical, paragenetic, and geochemical data on sulfidic mineralization from the Cínovec greisen-type deposit show that distribution of sulfides is irregular and not strictly bound to prevalent Li–Sn–W mineralization. Progressive development of metal contents in the reduced sulfide-bearing hydrothermal fluid proceeds from Zn–Cu–Sn to Pb–Bi–Ag and As–Sb. Late-stage sulfate- and fluorine-bearing fluids partly altered earlier mineralization but did not deposit significant ore content.

Metamorphic rocks affected by a fault have undergone chemical, mineralogical, and textural changes. The most significant is the enrichment in clay minerals (chlorite, kaolinite, and smectite). Geothermometry of the new chlorites made it possible to determine the temperatures of the processes (predominantly < 225°C), promoted by the fault dynamics (mainly fluid-related alterations). The retrograde alteration also affected the fluid-accessible zones of the original rocks, with growth of the same clay minerals.

This study evaluates leucogranites from the Ama Drime Massif, Dinggye, Tibet, as a potential raw material for high-purity quartz. Petrographic, geochemical, and purification analyses of two representative samples show that the rocks are mainly composed of quartz, albite, and K-feldspar. After purification, the quartz reached SiO₂ contents of 99.996 % and 99.995 %, indicating promising potential as a supplementary high-purity-quartz resource.

Erzwiesite, ideally Ag₈Pb₁₂Bi₁₆S₄₀, Z = 1, is a new sulfosalt mineral discovered in the Erzwies mining area, Gastein Valley, Salzburg Province, Austria. The empirical formula is (Ag,Cu)_8.23(Pb,Cd)_11.33(Bi,Sb)_16.31 (S,Te,Se)_40.03 (based on 76 apfu). Erzwiesite crystallises in space group Cmcm (a = 4.085(5), b = 13.462(15), c = 33.92(4) Å, and V = 1866(4) ų). Erzwiesite is the first natural (8:8) homologue of the lillianite homologous series and is named after its type locality.

There is no short summary.

This paper describes the new mineral plumbogottlobite from the Glücksstern mine, Gottlob Hill, Friedrichroda, Gotha District, Thuringia, Germany. It occurs as thick, square, orange-brown, tabular crystals up to about 0.2 mm in diameter. The mineral is the lead (Pb) analogue of the mineral gottlobite, which occurs at the same locality and is identical in appearance. Plumbogottlobite is a late-stage, low-temperature hydrothermal mineral occurring on baryte and hausmannite.

Lopatkaite, ideally Pb₁₀As₂Sb₆S₂₂ (Z = 4), is a new arsenic-bearing sulfosalt species found in the Madoc deposit, Taylor Pit, Ontario, Canada. Associated minerals in the holotype specimen are boulangerite, veenite, and sterryite, all embedded in a calcite matrix. The ideal formula may be derived from the ideal boulangerite formula, Pb₁₀Sb₈S₂₂ (Z = 4), by a substitution of 2Sb with 2As. Lopatkaite is a homeotype of boulangerite and a new member of the rod-based family of sulfosalts. 

This study shows that calcite can trap elements similar to radioactive substances very effectively under natural conditions. By studying a sample formed under nuclear-waste-repository-like conditions, it was found that certain crystal parts hold over 200 times more of these elements. This happens through multiple processes, helping to safely store harmful substances even in low-salt environments, which is important for nuclear waste safety.