Belmonteite, CaMn₂(AsO₄)₂(H₂O)₅·2H₂O, is a new mineral discovered in the Mn ore deposits of eastern Liguria (Italy). Its crystal structure shows {010} layers of six-fold-coordinated Mn atoms decorated on both sides by (AsO₄) groups and Ca atoms and connected through H bonds. The genesis of this mineral is related to the circulation of As-rich oxidizing fluids within the Mn ore deposits. The name honors Donato Belmonte for his contribution to the knowledge of the mineralogy of Liguria.

We studied a newly discovered silver-rich mineral from an ore deposit in central China to understand how silver is stored in nature. Using microscopy, chemical, and crystal-structure tests, we found that this mineral is a new species with a unique tellurium-rich structure. Our results show that tellurium helped trap and concentrate silver in hot mineral-forming fluids, offering new clues to how silver-rich deposits form.

We developed a novel experimental setup to investigate the transport of Li and B between two melt reservoirs that were connected only via a fluid phase. This was used to simulate fluid exsolution occurring during late-stage pegmatite formation. We found that both Li and B were transported via the fluid, but the observed transport rates were low. It was shown experimentally that the Li isotopes fractionate between melt and fluid with the fluid being preferentially enriched in the heavier ⁷Li.

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.