The study, published in Frontiers in Geochemistry, examined mine wastes from two strikingly different legacy mining regions: the town of Cobalt in Ontario, Canada, and three historic mine sites in Cornwall, England. Despite vast differences in geology, ore type, and processing methods spanning a millennium of mining history, the researchers found that cobalt in both locations showed consistently high potential for mobilization — meaning it could readily dissolve and travel into aquatic environments where it might enter the food chain.

“The concentrations we found at Cobalt, Canada were extraordinary,” the research indicates, with high-grade Nipissing tailings containing up to 5,630 milligrams of cobalt per kilogram of material — roughly 900 times higher than the Cornwall sites. Even the low-grade tailings at Cobalt reached 1,230 milligrams per kilogram, dwarfing the averages of 40, 76, and 59 milligrams per kilogram found at Poldice, Wheal Unity, and Dolcoath mines in Cornwall respectively. These concentrations far exceed residential soil quality guidelines set by regulatory bodies in Ontario, Canada, the United States, and the European Union.

The research team, led by Gabriel Ziwa of the Camborne School of Mines at the University of Exeter, employed a sophisticated battery of analytical techniques to understand not just how much cobalt was present, but in what chemical forms. Using X-ray diffraction, scanning electron microscopy, and electron microprobe analysis, they identified the specific minerals hosting the cobalt — a crucial step because a metal locked inside a stable crystal is far less dangerous than one sitting on a mineral surface ready to dissolve at the first change in water chemistry.

At Cobalt, Canada, the picture was dominated by a striking pink mineral called erythrite — a cobalt arsenate that formed as needle-like crystals growing on silicate and carbonate grains throughout the tailings. This secondary mineral, containing roughly 20.8 percent cobalt by weight, proved to be the most widespread cobalt-bearing phase at the site. The researchers also identified primary cobalt minerals including cobaltite, safflorite, and skutterudite, alongside cobalt incorporated into arsenopyrite, loellingite, pyrite, and chalcopyrite. Secondary phases such as arseniosiderite, scorodite, and iron oxyhydroxides also harboured significant cobalt concentrations.

In Cornwall, by contrast, no dedicated cobalt minerals were found at all. Instead, cobalt existed only as a trace component — typically less than one percent by weight — hidden inside common sulfide minerals like pyrite, chalcopyrite, and arsenopyrite, and in secondary phases such as scorodite and iron-manganese oxyhydroxides. Yet this difference in mineralogical hosting made almost no difference to the metal’s behaviour when subjected to sequential extraction testing.

The most alarming result came from the BCR sequential extraction analysis, a standardized European protocol that subjects mine waste to progressively stronger chemical leaches to simulate what might happen under different environmental conditions. In both the Canadian and British samples, an average of 46 percent of the total cobalt was extracted in the very first, mildest step — the “exchangeable” fraction that represents metal most easily dissolved by slight changes in acidity. This means nearly half the cobalt in these wastes is sitting in a form that could be released into water with only minor pH shifts.

Applying the Risk Assessment Code framework developed by Perin and colleagues, the researchers classified cobalt in the Cornwall samples as ranging from high risk to very high risk, with individual samples reaching exchangeable fractions of up to 62 percent. At Cobalt, Canada, values ranged from 28 to 58 percent, placing the metal in medium to very high risk categories. According to the RAC guidelines, metals exceeding 50 percent in the exchangeable fraction are considered to easily enter the food chain — a classification that directly implicates these mine wastes as potential vectors for human cobalt exposure through crops, livestock, and water supplies.

The chemistry behind this mobilization is well understood. At Cornwall’s acidic sites, where paste pH values ranged from 3.72 to 5.77, sulfide minerals like pyrite generate acid through oxidation, and any cobalt-bearing phases dissolve readily, releasing cobalt ions and arsenic oxyanions into solution. At Cobalt, Canada, the near-neutral pH of 7.50 to 7.84 currently stabilizes erythrite within its thermodynamic stability field — but the researchers warn this equilibrium is fragile. A shift toward acidity, whether from changing oxidation conditions or altered hydrology, could dissolve the erythrite and release its cobalt payload. The iron and manganese oxyhydroxides that scavenge cobalt in both locations are themselves thermodynamically unstable under reducing conditions, meaning buried or waterlogged wastes could also release their stored metal.

What makes this research particularly significant is its implication for the future. Cobalt demand is projected to surge as electric vehicle adoption accelerates globally, and governments worldwide have designated it a strategic resource. Yet the environmental behaviour of cobalt in mine waste has been remarkably understudied compared to metals like arsenic or lead. The Exeter team’s finding that cobalt behaves similarly across such geologically different settings — a five-element silver-cobalt-nickel vein deposit in Precambrian rocks versus polymetallic tin-copper-arsenic veins in Devonian-Carboniferous host rocks — suggests that the metal’s mobility in mine waste may follow predictable patterns worldwide. If confirmed by further research, this would mean that every new cobalt mine opening today is generating waste with the same latent capacity to contaminate water and food chains that century-old sites in Canada and England are only now revealing.

Subject of Research: Geochemistry and mineralogy of cobalt mobility in legacy mine wastes from Cobalt, Canada and Cornwall, England

Article Title: Geochemistry and mineralogy of Cobalt in mine wastes: examples from Cobalt, Canada and Cornwall, England

Article References: Ziwa, G., Crane, R., & Hudson-Edwards, K. A. (2025). Geochemistry and mineralogy of Cobalt in mine wastes: examples from Cobalt, Canada and Cornwall, England. Frontiers in Geochemistry, 3, Article 1543695. https://doi.org/10.3389/fgeoc.2025.1543695

Image Credits: AI Generated

DOI: 10.3389/fgeoc.2025.1543695

Keywords: cobalt, mine waste, tailings, geochemistry, mineralogy, erythrite, sequential extraction, mobility, critical raw materials, contamination, Cornwall, Ontario

The distinction between approval and full description is worth emphasizing for readers unfamiliar with mineralogical practice. When the commission approves a species, the newsletter publishes a standardized set of data: the name, the ideal formula, a two- or three-letter symbol, the type locality, the authorship of the proposal, the crystal system and space group, unit-cell parameters, the strongest lines of the X-ray powder diffraction pattern, and the repository holding the type material. What the newsletter deliberately withholds is any interpretive narrative. The commission’s stated policy is that no information beyond these essentials will be released, and the proposing authors remain obligated to publish a complete description of the mineral, including its occurrence, paragenesis, physical properties, optical behavior, and the analytical details underpinning the formula, in a peer-reviewed venue. This two-stage arrangement protects the priority of the discoverers while ensuring that the mineralogical community receives the essential identifiers quickly and in a uniform format that can be added month by month to the commission’s public database.

The type specimen itself is the anchor of the entire system. Every approved species in this newsletter is accompanied by a designated repository and catalogue number, whether that is the Museo di Scienze della Terra in Bari, the National Geological Museum of China in Beijing, the Natural History Museum of Los Angeles County, the Carnegie Museum of Natural History in Pittsburgh, the National Museum of Nature and Science in Tsukuba, the Bavarian State Mineral Collection in Munich, or the Muséum Cantonal des Sciences Naturelles in Lausanne. The type material is the physical reference against which all future identifications of the species are measured. Where a proposal lists both a holotype and a cotype, or several cotype specimens distributed among institutions, this reflects cases where the available material was divided or where different portions of the collection carry complementary analytical value. The practice of depositing type material in publicly accessible collections is one of the quiet strengths of mineralogical nomenclature, because it means that disputes about the identity of a species can, in principle, be resolved by direct examination of the original grains decades or centuries later.

Several of the newly approved species illustrate how modern mineral discovery increasingly depends on analytical techniques capable of interrogating very small volumes of material. Proxicosahedrite, found in a micro-spherule of a micrometeorite collected on Mount Gariglione in Calabria, Italy, is a case in point. Its formula, Al52Cu30Fe11Si7, and its cubic structure with a unit-cell edge of about 12.34 Å identify it as a member of the family of complex metallic alloys whose synthetic analogues have long been studied for their unusual quasiperiodic and approximant structures. The discovery of such phases in extraterrestrial material continues a line of research in which natural samples, often formed under transient high-energy conditions during atmospheric entry or impact, are found to reproduce structures first encountered in the laboratory. The prefix prox- in the name alludes to this proximity to the related cosahedrite-type arrangement, and the determination of the structure from a spherule only micrometers across required electron diffraction methods rather than conventional single-crystal X-ray work, a technique that has become routine in the characterization of sub-millimeter mineral grains.

Wusiheite, by contrast, comes from a very different geological setting: the Wusihe lead-zinc deposit in Sichuan Province, China. Its formula, BaGe(Ge3O9), places it in the benitoite group, and the newsletter explicitly identifies it as the Ge-Ge analogue of benitoite itself, the famous barium titanium silicate that serves as the state gemstone of California. Benitoite-type structures consist of rings of corner-sharing tetrahedra arranged in trigonal symmetry, and the substitution of germanium for silicon and titanium in these tetrahedral sites produces a mineral whose framework is topologically identical to benitoite but chemically distinct. Germanium minerals are rare in nature because germanium is a trace element in most crustal rocks, concentrating only in specific settings such as oxidized sulfide deposits, and each new natural germanate therefore adds to a small but scientifically valuable inventory of phases that probe the crystal-chemical behavior of germanium at high valence states.

Bromammoniac, the bromine analogue of salammoniac, is another example of a species whose significance lies less in its complexity than in the environment that produced it. Ammonium halides are among the most chemically simple minerals known, and salammoniac itself has been recognized for centuries, often forming as sublimates around volcanic fumaroles and burning coal seams. The new bromide phase was recovered from an active vent in burning bituminous shale of the Monterey Formation on a sea-cliff talus slope along the Pacific coast at Hope Ranch, Santa Barbara, California. Spontaneous combustion of organic-rich shale generates a low-temperature but chemically aggressive environment in which volatile components, including ammonia and hydrogen bromide derived from the burning organic matter and saline fluids, combine and crystallize as the gases cool. Such combustion metamorphic settings are ephemeral, often lasting only years or decades, and minerals from them are correspondingly rare in the literature, which makes their formal documentation all the more important for understanding the full range of conditions under which crystalline phases can form naturally.

Usagreite, from the Mariquita mine in Badajoz Province, Spain, belongs to a different chemical world altogether. Its formula, Hg2+2S2, and its monoclinic structure place it among the mercury sulfatosalts, a family of compounds in which mercury-sulfur bonds coexist with sulfate groups. The newsletter describes it as the sulfate analogue of alexearlite, and the structural determination confirms that the mercury-sulfur framework persists while the anion chemistry changes. Mercury minerals of this kind typically form in the supergene oxidation zone of mercury deposits, where cinnabar and other primary sulfides are weathered and the resulting mercury is redistributed into secondary phases. The Mariquita mine, in the Extremadura region, is one of the historic mercury mining districts of the Iberian Peninsula, and the discovery of a new species there underscores how even long-worked localities can still yield minerals unknown to science when modern analytical methods are applied to old collections or to freshly exposed oxidation zones.

Aluminomacfallite, from the Kokuriki mine in Hokkaido, Japan, extends a different branch of nomenclature. The suffix -macfallite refers to an existing species, and the prefix aluminomarks the new mineral as its aluminium analogue, in which aluminium replaces the trivalent cation of the parent species in the sorosilicate framework defined by the (SiO4)(Si2O7) groups. The systematic naming of analogues in this way is governed by strict IMA rules: an analogue differs from its parent species only in the dominant occupancy of one or more crystallographic sites, and the prefix must unambiguously identify the substituting element. This convention allows the mineralogical literature to grow in a controlled way, with each new analogue occupying a predictable position in a chemical series rather than requiring an entirely new root name.

Lincioite, from the Lagoscuro mine in Liguria, Italy, is assigned to the hydrotalcite supergroup, a large family of layered double hydroxides characterized by positively charged brucite-like layers interleaved with anions and water molecules. The formula of lincioite, Ni2+Fe3+O2(OH)10·3H2O, shows the characteristic alternation of divalent and trivalent cations in the layers with carbonate occupying the interlayer, and its trigonal R3m symmetry with a basal spacing of about 22.4 Å is typical of the group. Layered double hydroxides are of considerable interest beyond mineralogy because of their anion-exchange properties and their use as catalyst precursors and corrosion inhibitors, and natural occurrences such as lincioite, formed in the oxidation zone of a serpentinite-hosted ore deposit, provide reference points for understanding how these synthetic materials weather and transform over geological time.

Wolfgangpauliite, named for the physicist Wolfgang Pauli, is a uranyl phosphate from the Bois Noirs-Limouzat mine in the Forez massif of France, a locality known for its uranium mineralization. Its formula, Ca1.5K(H2O)5.5[(UO2)3O2(PO4)2], and its monoclinic C2/m structure relate it chemically and structurally to françoisite-(Ce), another uranyl phosphate with a similar sheet architecture. Uranyl phosphates form one of the most structurally diverse families of secondary minerals, arising wherever hexavalent uranium from primary ores migrates in oxidizing groundwater and encounters phosphate-bearing solutions. Their structures are built from uranyl pentagonal bipyramids linked by phosphate tetrahedra into sheets, with interlayer cations and water molecules occupying the space between. The diversity of this family, which now numbers well over a hundred species, reflects the flexibility of the uranyl-phosphate sheets and the variety of cations that can occupy the interlayer, and each new member refines the crystal-chemical systematics used to predict uranium mobility in contaminated environments.

Sainzbarandaite, from the Qinglong antimony deposit in Guizhou, China, is a calcium aluminium fluoride hydrate with the formula Ca7Al4F26(H2O)5, related to gearksutite and carlhintzeite. Fluoride minerals of this kind form in the near-surface alteration of fluorine-rich ore systems, and the Qinglong deposit, one of the world’s largest antimony producers, provides the chemical environment in which calcium, aluminium, and fluorine combine in unusual proportions. The large unit cell, with c close to 30 Å, indicates a complex layered structure, and the determination of that structure from such a rare phase demonstrates the power of modern single-crystal methods even when only minute crystals are available.

Finally, rozhdestvenskayaite-(Fe), from the Bianjiadayuan deposit in the Great Hinggan Range of China, belongs to the sulfosalt group, a family of phases built from packed metal-sulfur frameworks in which silver, antimony, and iron combine in complex stoichiometries. The Levinson-style suffix -(Fe) indicates the dominant trivalent cation in the formula, following the convention used for rare-earth and other variable-valence minerals. Sulfosalts are among the most structurally intricate of all minerals, and the revision of their nomenclature over recent decades has been one of the commission’s major undertakings, with entire subcommittees devoted to reconciling old names with new structural data. The approval of a new sulfosalt species therefore carries implications beyond the single mineral, contributing to a systematic framework that underpins the classification of ore deposits and the interpretation of their genesis.

Taken together, the eleven approvals in this newsletter span nearly the whole breadth of mineralogical interest: an extraterrestrial metallic alloy, a germanate from a sulfide deposit, a combustion sublimate, a mercury sulfatosalt, a sorosilicate analogue, a layered double hydroxide, a uranyl phosphate, a fluoride, and a sulfosalt. They also span the globe, from Calabria to Hokkaido, from Sichuan to Extremadura, from Liguria to the Forez massif, and from Santa Barbara to Inner Mongolia. That breadth is not accidental. The commission’s monthly newsletters function as a running census of the mineral kingdom, and each entry, however terse, records a moment at which a new arrangement of atoms was recognized, verified, named, and committed to the permanent record of science.

Subject of Research: IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) – Newsletter 93

Article Title: IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) – Newsletter 93

Article References: Bosi, F., Hatert, F., Pasero, M., & Mills, S. J. (2026). IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) – Newsletter 93. European Journal of Mineralogy, 38(5), 629-633. https://doi.org/10.5194/ejm-38-629-2026

Image Credits: AI Generated

DOI: 10.5194/ejm-38-629-2026

Keywords: mineralogy, IMA, new minerals, CNMNC, crystallography, micrometeorite, quasicrystal, uranium minerals, tetrahedrite, benitoite, X-ray diffraction, mineral nomenclature

The research, led by Raghda Emera and colleagues at the Harold Vance Department of Petroleum Engineering, focuses on serpentinization, the hydrothermal alteration of ultramafic rocks such as peridotite and dunite. When olivine, the dominant mineral in these rocks, reacts with water at elevated temperatures, ferrous iron is oxidized to ferric iron, and molecular hydrogen is released as a byproduct. The process has long been documented at mid-ocean ridge hydrothermal fields such as Lost City and Rainbow, but translating that natural phenomenon into a predictable, engineered energy resource has remained stubbornly difficult.

One of the study’s clearest messages concerns the identity of the reacting mineral itself. Olivine is a solid solution between a magnesium-rich end member, forsterite, and an iron-rich end member, fayalite. Prior thermodynamic work suggested that iron-rich olivine generates two to ten times more hydrogen per mole than magnesium-rich varieties, but direct experimental isolation of this effect had been lacking. The Texas A&M group ran controlled experiments on pure fayalite, pure forsterite, and an equal mixture of the two under identical conditions of 100 degrees Celsius, 33 bar, and near-neutral pH, removing all confounding variables.

The results were striking. Pure fayalite produced the highest hydrogen yields of any powdered sample, roughly five times more than a natural peridotite and more than double the yield of the 50-50 mixture. Pure forsterite, by contrast, generated no detectable hydrogen at the experimental temperature. The team’s calibrated kinetic models, which combine thermodynamic equilibrium calculations with Arrhenius-type rate laws, matched the laboratory data closely, with a maximum relative error of just 0.14. When the model was pushed to hypothetical compositions, a rock containing 61.5 percent fayalite produced nearly three times the hydrogen of a natural peridotite with 21 percent fayalite, confirming that iron availability is the single strongest lever on hydrogen generation.

Temperature ranked second in importance. Sensitivity simulations showed that raising temperature from 50 to 100 degrees Celsius increased simulated hydrogen generation roughly fourfold for pure fayalite, with smaller gains for mixed compositions. In the core-scale model, doubling the temperature from 100 to 200 degrees Celsius nearly doubled the peak hydrogen concentration, shifting the peak to around day three instead of days seven to nine. This steep dependence follows classic Arrhenius kinetics, in which the rate-limiting olivine dissolution step carries an activation energy of 60 to 80 kilojoules per mole, enough to produce a tenfold rate increase for roughly every 40 degrees Celsius of warming.

The pressure and pH results were more nuanced, and in some cases counterintuitive. Laboratory batch experiments appeared to show less hydrogen in the gas phase at higher pressures, but the authors traced this to an experimental artifact: pressurizing the reactor with nitrogen diluted the headspace and pushed more hydrogen into the dissolved phase. Back-calculations accounting for the nitrogen inventory still indicated a genuine decline in yield at the highest pressures in the batch tests, while the kinetic models, which free the chemistry from those artifacts, showed a modest positive effect of pressure. The team emphasizes that pressure is a secondary control compared to mineralogy and temperature.

pH effects turned out to depend on pressure, a coupling that single-variable experiments often miss. At 35 bar, the moderately alkaline pH of 8.5 consistently outperformed pH 9.5, reaching 431 ppm hydrogen at 28 days versus just 59 ppm. At 70 bar, the ranking flipped early in the experiment before converging, and pH 10.5 performed worst throughout. The authors suggest that higher alkalinity suppresses hydrogen generation under these conditions, likely by limiting mineral dissolution or promoting passivating coatings of secondary minerals on reactive surfaces.

Perhaps the most consequential finding involves scale. The team compared the powdered batch experiments with a flow-through experiment on a fractured core of Twin Sisters dunite, a nearly pure olivine rock from Washington State containing 92.3 percent olivine. The core was split, propped open with a roughly one-millimeter fracture, and flooded with synthetic brine at 100 degrees Celsius while effluent gas was analyzed continuously by micro gas chromatography. Hydrogen rose to a peak near day seven and then declined, mirroring the model closely during the first eight days but diverging sharply afterward, with relative errors eventually exceeding 700 percent.

That divergence is scientifically revealing rather than a failure. In powdered systems with abundant, uniform mineral-fluid contact, reaction kinetics control the outcome. In fractured intact rock, transport takes over: serpentinization products such as chrysotile and magnetite precipitate on reactive surfaces, the roughly 40 to 44 percent solid volume expansion of serpentinization can occlude fracture apertures, and flow may channel away from unreacted mineral. The authors identify evolving reactive surface area, permeability feedback, and geomechanical deformation as the highest-priority additions to future models before laboratory numbers can be trusted at reservoir scale.

For the nascent geological hydrogen sector, the practical takeaway is concrete: exploration and stimulation programs should prioritize screening formations for fayalite, or iron-rich olivine content, as the dominant predictor of hydrogen yield, while remembering that the kinetically accessible maxima implied by powdered experiments require open, stimulated flow conditions to approach underground. The study, published in Frontiers in Geochemistry and partly funded by the U.S. Department of Energy’s ARPA-E program, provides a controlled dataset and a validated modeling framework that together mark a significant step toward making Earth’s own hydrogen factory predictable.

Subject of Research: Hydrogen generation from water-rock reactions in ultramafic rocks

Article Title: Experiments and geochemical modeling of hydrogen generation during water–rock reactions: effects of mineralogy and physicochemical conditions

Article References: Emera, R., Angelina, N. M., Gyaubea Matey-Korley, V., Isah, A., & Okoroafor, E. R. (2026). Experiments and geochemical modeling of hydrogen generation during water–rock reactions: effects of mineralogy and physicochemical conditions. Frontiers in Geochemistry, 4, Article 1913188. https://doi.org/10.3389/fgeoc.2026.1913188

Image Credits: AI Generated

DOI: 10.3389/fgeoc.2026.1913188

Keywords: geological hydrogen, serpentinization, olivine, fayalite, forsterite, ultramafic rocks, geochemical modeling, reactive transport, Arrhenius kinetics, mineralogy, hydrothermal reactions, pH

Saprolite is the soft, clay-rich, rock-like material that forms when bedrock weathers in place, retaining the original texture of the parent rock while its minerals are progressively transformed. It represents the front line of supergene weathering, the zone where atmospheric water, oxygen, and organic acids first attack fresh rock. Because saprolite sits above the more intensively leached soils below and the unweathered bedrock above which it forms, it offers a natural laboratory for catching minerals in the act of their first chemical defeat. It was precisely in this early-stage setting that Li and Zhou examined zircon grains, using nanoscale analytical techniques capable of resolving features far below the resolution of conventional microscopy.

The central finding is stark in its simplicity. Zircon does not wait until it has been battered, fractured, and radiation-damaged before it starts to weather. Even crystalline zircon, the variety long considered effectively immune to surface processes, undergoes dissolution during early saprolitic weathering. The decomposition does not proceed by wholesale destruction of the grain. Instead, the researchers document a coupled two-step mechanism: the primary, crystalline zircon dissolves, and in its place a secondary, amorphous zircon precipitates. In other words, the mineral survives, but its identity is transformed, the original crystal lattice being replaced by a new, non-crystalline zirconium-rich material that inherits the external shape of the grain it replaces.

This dissolution–reprecipitation pathway is a familiar style of alteration in many silicate minerals, but documenting it in zircon at the onset of weathering carries unusually broad consequences. The nanoscale examination reveals that the newly precipitated amorphous zircon is not chemically identical to what it replaced. Elements that do not fit comfortably into the zircon crystal formula, referred to as non-formula elements, are taken up during precipitation and structurally incorporated into the secondary material. Among these are uranium, thorium, and heavy rare earth elements, the very components that make zircon such a valuable recorder of geological history and such a focus of ore-deposit research.

The incorporation of uranium and thorium into the secondary zircon sets up a self-reinforcing cycle of degradation. Both elements are radioactive, and their decay emits alpha particles that progressively shatter the crystal structure from within, a process known as metamictization. A metamict zircon, its lattice already riddled with radiation damage, is far more susceptible to dissolution than a pristine crystal. The new study therefore describes an accelerating feedback: weathering produces amorphous secondary zircon enriched in uranium and thorium, those elements drive metamictization, and metamictization in turn promotes further dissolution of the grain. What was once imagined as a one-way street toward preservation becomes a dynamic loop of destruction and reconstitution.

The implications reach into several corners of the Earth sciences simultaneously. For geochronology, the study raises the possibility that zircon dates and trace-element signatures from weathered terrains may have been subtly reset or modified during saprolite formation, even in grains that appear optically fresh and crystalline under the microscope. For sedimentary provenance studies, which rely on detrital zircon populations to trace the movement of sediments across continents, the finding suggests that some chemical information may be altered before grains ever reach a depositional basin. And for economic geology, where zircon and its hosted heavy rare earth elements are increasingly treated as critical mineral resources, the demonstration that weathering can redistribute and re-incorporate these elements at the nanoscale adds a new dimension to models of how such deposits form and evolve.

The study also speaks to a very different application: the proposed use of zircon-like structures as ceramic hosts for immobilized nuclear waste. Synthetic zircon and related phases have been considered attractive waste forms precisely because natural zircon survives for billions of years, apparently locking radioactive elements into a durable lattice. The new results complicate that narrative. If natural zircon takes up uranium and thorium into amorphous secondary phases during weathering, and if those incorporated radionuclides then accelerate the breakdown of the host through metamictization, then the long-term behavior of zircon-based waste forms in surface or near-surface environments deserves renewed scrutiny. The mineral’s celebrated durability, the authors suggest, cannot be taken for granted in supergene settings.

None of this means that zircon is fragile in any ordinary sense. The weathering documented by Li and Zhou is an onset, a beginning, captured at the nanoscale in the earliest weathering profile. Zircon grains still persist through vast stretches of geological time, and the mineral’s utility as a chronometer of deep time remains intact for the countless samples that have never passed through a saprolitic zone. But the study redraws the boundary between the durable and the reactive. The conventional picture, in which crystalline zircon is inert until radiation damage renders it vulnerable, is replaced by one in which weathering attacks pristine crystals directly, converting them grain by grain into amorphous secondary zircon while quietly reorganizing their chemical cargo.

Methodologically, the work is a demonstration of why nanoscale examination matters. Features that decide whether a mineral preserves or releases its records, the dissolution surfaces, the precipitated amorphous domains, the structural sites where uranium, thorium, and heavy rare earth elements come to rest, are invisible to the standard tools of petrography. Only by interrogating zircon at the scale of its atomic architecture could the authors distinguish primary crystalline material from its secondary amorphous replacement and trace the uptake of non-formula elements into the new phase. The study is a reminder that some of the most consequential processes in geochemistry operate at scales far below those at which minerals are routinely described.

Li and Zhou conclude that in supergene environments zircon would steadily weather, and they call for further evaluation of the geological and environmental applications that depend on the mineral’s assumed permanence. That call is likely to resonate widely. Zircon underpins some of the most trusted tools in the Earth sciences, from the oldest known terrestrial crystals to the dating of the Moon-forming era, and any revision to its behavior at Earth’s surface ripples outward through those applications. The new work does not overturn the zircon record; it refines it, replacing a simple story of indestructibility with a more nuanced account of slow, nanoscale transformation, one in which the planet’s most reliable timekeeper is revealed to be quietly rewriting its own pages from the moment weathering begins.

Subject of Research: Early-stage decomposition of crystalline zircon during saprolitic weathering

Article Title: Onset of zircon decomposition during saprolitic weathering

Article References: Li, M. Y. H., & Zhou, M.-F. (2026). Onset of zircon decomposition during saprolitic weathering. Communications Earth & Environment. https://doi.org/10.1038/s43247-026-04140-4

Image Credits: AI Generated

DOI: 10.1038/s43247-026-04140-4

Keywords: zircon, saprolite, weathering, geochemistry, mineralogy, metamictization, uranium, thorium, rare earth elements, dissolution-precipitation, supergene environments, nanoscale analysis

The April 2026 approvals open with piilonenite-(Nd), a hydrated sodium-neodymium carbonate with the ideal formula NaNd(CO3)2(H2O)3, discovered at the famous Poudrette (Demix) quarry on Mont Saint-Hilaire in Quebec, Canada. Proposed by Inna Lykova of the Canadian Museum of Nature and colleagues, the mineral represents an entirely new structure type, crystallizing in the orthorhombic space group P212121 with unit-cell parameters a = 6.791(1), b = 17.135(3) and c = 6.436(1) Å. Mont Saint-Hilaire has long been celebrated as one of the most mineralogically diverse localities on the planet, and the arrival of a new structure type from its alkaline rocks underscores why the quarry continues to fascinate collectors and crystallographers alike. The type specimen is deposited in the collections of the Canadian Museum of Nature in Ottawa under catalogue number CMNMC 93393.

The second April approval, kristekite, comes from a very different setting: the mine dump of shaft no. 11A near Bytíz in the Příbram ore district of Central Bohemia, Czech Republic. With the ideal formula Cu2(H2O)4(UO2)(SeO3)3 · 4H2O, kristekite is a hydrated copper uranyl selenite, chemically related to marthozite, and it crystallizes in the monoclinic space group P21/m. The proposal, led by Jakub Plášil of the Institute of Physics of the Czech Academy of Sciences together with Pavel Škácha, Jiří Sejkora, Radek Škoda and Radana Vrtišková, reflects the growing recognition of mine dumps as secondary-mineral laboratories, where the interaction of groundwater with ore and smelting residues generates exotic compounds that nature rarely produces elsewhere. The type material rests in the National Museum in Prague under catalogue number P1P 46/2025.

Perhaps the most eye-catching of the April approvals is magnesiochangesite-(Ce), with the ideal formula (Ca8Ce)□Mg(PO4)7, because its type locality is not on Earth at all. The mineral was found in lunar meteorite Pakepake005, discovered in the Taklamakan desert of Xinjiang, China. A member of the cerite supergroup, it is trigonal, space group R3c, with a = 10.3813(4) and c = 37.278(1) Å, and its structure has been fully determined. The large international team was coordinated by Yanjuan Wang of the China University of Geosciences and Fabrizio Nestola of the University of Padua, and the type specimen is held at the Geological Museum of China in Beijing under catalogue number GMCTM2025021. Minerals approved from meteorites carry particular scientific weight, because their compositions and structures preserve clues about the parent body’s geological history, and a cerite-supergroup phosphate in lunar material speaks to the complex chemistry of the Moon’s crust.

The May 2026 approvals begin with bernwoodite, Ca5TiAl2Si2O14, a member of the perovskite supergroup found as an inclusion inside a diamond from the Rio Sorriso placer in the Juina area of Mato Grosso, Brazil. Diamonds from Juina are renowned as messengers from the deep Earth, transporting fragments of the lower mantle and transition zone to the surface, and inclusions such as bernwoodite are among the few direct samples of those inaccessible depths. The mineral is monoclinic, space group C2/c, with a = 9.190(1), b = 5.2594(4) and c = 21.846(4) Å and β = 97.84(2)°. The proposal was led by Nester Korolev of the American Museum of Natural History, with co-authors including Ekaterina S. Kiseeva, Alena Aslandukova, George E. Harlow, Chi Ma, Yaakov Weiss, Alexander Kurnosov, Felix V. Kaminsky and Leonid Dubrovinsky. The type specimen is deposited at the American Museum of Natural History in New York under catalogue number AMNH#115649.

Two further May approvals came from Xiangping Gu and Hexiong Yang of the University of Arizona and their collaborators. Georgeliuite, Ca2Mn3(3+)O2(AsO4)3(H2O)2 · H2O, was found at the Jote mine in the Pampa Larga district of Tierra Amarilla, in Chile’s Atacama Region, and is the Mn3+ analogue of arseniosiderite; it is monoclinic, space group Cm, with type material split between the University of Arizona Alfie Norville Gem & Mineral Museum in Tucson, catalogue number 22747 (holotype), and the RRUFF Project, deposition number R250055 (cotype). Sombrereteite, NaCa3(Al7Si9)O32, was recovered from the Sombrerete iron meteorite, found in 1958 at Cerro del Sombreretillo in Zacatecas, Mexico, and is chemically the sodium analogue of wodegongjieite; it is monoclinic, space group C2/c, with its type specimen at the Geological Museum of China in Beijing, catalogue number GMCTM2025019. The pairing of a terrestrial mine and an extraterrestrial iron meteorite in a single month illustrates the breadth of environments from which new minerals now emerge.

The final new species, leishmanite, approved as IMA no. 2026-002, is a barium uranyl oxide hydroxide hydrate with the ideal formula Ba(H2O)4[(UO2)3O2(OH)3]2 · 3H2O, discovered on the northern slope of the Grand Alou valley south of the Dent de Nendaz in Valais, Switzerland. Proposed once again by Jakub Plášil, with Radek Škoda, Stefan Ansermet and Nicolas Meisser, leishmanite is closely related to billietite and crystallizes in the orthorhombic space group Pmn21, with a = 12.079(2), b = 15.096(3) and c = 7.155(2) Å. The type material is deposited at the Naturéum in Lausanne under catalogue number MGL101918. Uranyl minerals such as leishmanite and kristekite are of intense interest beyond pure mineralogy, because their layered structures and ion-exchange behavior inform models of uranium mobility in contaminated ground and the long-term behavior of nuclear waste.

Beyond the new species, Newsletter 91 records two significant nomenclature decisions approved in March 2026. Proposal 25-B formally redefines the stilpnomelane group, whose members share the general formula A4M48Si64Al8216 · nH2O, where A is potassium, sodium, calcium or barium and M is a mix of iron, manganese, magnesium, aluminum and zinc. Stilpnomelane itself is now defined by the end-member formula K4Fe2+48[Si64Al8]O164(OH)52 · nH2O, while lennilenapeite is redefined as its manganese analogue. As a consequence of the tightened definitions, two long-recognized names are discredited: ekmanite, which turns out to be a stilpnomelane with only minor manganese, and franklinphilite, which proves to be a mixture of lennilenapeite and nelenite rather than a distinct species. Discreditation is a routine but consequential act, removing names from textbooks and databases worldwide.

Proposal 26-A addresses a problem that occasionally afflicts historically important minerals: inadequate or missing original type material. Gadolinite-(Y), first described from the famous Ytterby locality in Sweden, the quarry that gave its name to four chemical elements, has now been assigned a neotype, a newly designated reference specimen that anchors the name for future generations. The neotype material, curated by Dan Holtstam, Alice Taddei, Hans-Jürgen Förster and Oona Appelt, is stored in the collections of the Swedish Museum of Natural History in Stockholm under catalogue number GEO-NRM LK6893, ensuring that the mineral whose discovery helped launch the chemistry of the rare earth elements rests on a firm modern footing.

The newsletter’s final section documents the second round of a systematic polish-up of the IMA List of Minerals, an executive decision by the commission following a similar exercise published years earlier in Newsletter 50. In most cases the changes are subtle but meaningful: subordinate constituents sharing parentheses with the dominant constituent are eliminated from ideal formulae, so that, for example, ankerite is now written CaFe2+(CO3)2 in direct parallel with dolomite, CaMg(CO3)2, and serpierite becomes CaCu4(SO4)2(OH)6(H2O)3, matching the pattern of devilline. Similar simplifications were applied to dozens of species, including aldridgeite, aluminocopiapite, azoproite, bannisterite, barquillite, borisenkoite, byrudite, chlorophoenicite, cyprine, eckhardite, fluorphvesuvianite, fritzscheite, gainesite, hloušekite, hydrombobomkulite, johnwalkite, laitakarite, lasnierite, lucabindiite, magnesioneptunite, magnesiorowlandite-(Y), mbobomkulite, mccrillisite, montroseite, murunskite, nordgauite, ohmilite, paraniite-(Y), the paratacamite series, plumboagardite, potassiccarpholite, putzite, thalcusite, thorutite, the yttrotungstites and zincobriartite. Questionable minerals and species belonging to supergroups covered by comprehensive subcommittee reports were deliberately excluded, since they require deeper reappraisal or have already been settled. The exercise may look like typographic housekeeping, but consistent ideal formulae are the backbone of mineral databases, thermodynamic modeling and automated crystallographic searches, and the commission’s routine publication of such updates in the European Journal of Mineralogy keeps the nomenclature of the roughly six thousand recognized mineral species transparent, verifiable and, in its own quiet way, remarkably viral among the collectors and researchers who follow each new name as it enters the official record.

Subject of Research: Approval of new mineral species and mineral nomenclature revisions by the IMA Commission on New Minerals, Nomenclature and Classification

Article Title: IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) – Newsletter 91

Article References: Bosi, F., Hatert, F., Pasero, M., & Mills, S. J. (2026). IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) – Newsletter 91. European Journal of Mineralogy, 38(3), 347-352. https://doi.org/10.5194/ejm-38-347-2026

Image Credits: AI Generated

DOI: 10.5194/ejm-38-347-2026

Keywords: mineralogy, IMA-CNMNC, new minerals, crystallography, lunar meteorite, diamond inclusions, uranium minerals, stilpnomelane, gadolinite, nomenclature, Mont Saint-Hilaire, European Journal of Mineralogy

The story of the new mineral begins with a specimen collected on 18 August 2000 by Elsa Pfenninger-Horváth and László Horváth in narrow apophyses — vein-like offshoots three to six centimetres wide — of the Poudrette pegmatite on level 8 of the quarry. The Poudrette pegmatite is the largest pegmatite ever observed at Mont Saint-Hilaire, an agpaitic alkaline igneous complex famed among collectors for producing hundreds of mineral species. Its apophyses radiate outward from the main body for tens of metres, entirely enclosed within an enormous hornfels xenolith, a baked block of country rock. Mineral assemblages shift dramatically across the pegmatite, ranging from silicate-dominated to carbonate-dominated zones, and it was in one of these late-stage carbonate-rich pockets that the thin, bladed crystals of piilonenite-(Nd) formed alongside siderite, calcite, microcline, sphalerite, garronite-Na, quartz, rutile and aegirine.

For years the material hid in plain sight under a placeholder identity. It was thought to be the unknown phase UK119 from Mont Saint-Hilaire, a mystery mineral probed repeatedly without success: Robert Gault analysed it with the electron microprobe in 1999, Joel Grice attempted to solve its crystal structure in 2000, Ralph Rowe collected powder X-ray diffraction data in 2007, and Igor Pekov made further structural attempts between 2009 and 2013. The new examination revealed that UK119 was never a single phase at all. At least two different minerals — piilonenite-(Nd) and an unrelated sodium–cerium carbonate — were mixed together in the same material, having formed at the same time, a coincidence that confounded every earlier attempt. Any information previously attributed to UK119 could therefore refer to either or both of the two phases.

Physically, piilonenite-(Nd) is unassuming. It forms thin, bladed crystals up to 600 micrometres across, colourless to white, with a white streak, vitreous lustre, perfect cleavage on {010} and an uneven fracture. The crystals are so thin and flaky that a Mohs hardness could not be measured, and the mineral shows no fluorescence under ultraviolet light. Its calculated density is 3.21 grams per cubic centimetre. Optically it is biaxial positive, with refractive indices α = 1.546, β = 1.616 and γ = 1.638 and a measured axial angle of 56 degrees. The mineral dissolves slowly in aqueous hydrochloric acid at room temperature with gentle effervescence — the tell-tale fizz of a carbonate releasing carbon dioxide.

Chemical analysis demanded care. Because the mineral is unstable under the electron beam, the team used a JEOL 8230 SuperProbe with a widened 30-micrometre beam to minimise element migration, applying time-dependent intensity corrections for sodium, yttrium and lanthanum. Seven analyses yielded an average composition dominated by neodymium oxide at 23.90 weight percent, with significant cerium, samarium, praseodymium and gadolinium, plus a small yttrium contribution. The empirical formula, calculated on the basis of two cations, is Na1.00(Nd0.48Ce0.17Sm0.13Gd0.07Pr0.06Y0.05La0.02Dy0.02)(CO3)2(H2O)3 — confirming neodymium as the dominant rare earth element. Water and carbon dioxide contents were calculated from stoichiometry because so little material was available for direct measurement. Intriguingly, several areas within the crystals showed extraordinarily high yttrium, up to 18.4 weight percent Y2O3, hinting at a possible yttrium-dominant analogue of piilonenite lurking within the same tiny crystals.

Infrared spectroscopy filled in the structural picture that chemistry alone could not. The Fourier transform infrared spectrum, collected on a microsample pressed in a diamond anvil cell, shows O–H stretching bands between 3105 and 3230 wavenumbers and an H–O–H bending band at 1694 wavenumbers, confirming molecular water, along with C–O stretching vibrations of carbonate groups between 1356 and 1460 wavenumbers. A shoulder at 3420 wavenumbers points to hydroxyl anions, while weak bands at 1061 and 1091 wavenumbers reveal that some carbonate groups are polarised — a mode that would be forbidden in perfectly symmetric, threefold-axis carbonate groups. These spectroscopic fingerprints corroborated the presence of water molecules at three distinct crystallographic sites, later confirmed by bond-valence calculations based on hydrogen-bond distances.

The crystal structure itself proved the hardest prize. Previous structural attempts by Grice and Pekov had failed because the crystals diffract extremely poorly, bent as they are. Laboratory single-crystal diffractometers got the team nowhere, so they turned to synchrotron radiation at the Advanced Light Source in Berkeley, using beamline 12.2.1. Even there the data were poor, with split reflections and streaking across the diffraction pattern. Nevertheless, the team solved the structure in the orthorhombic space group P212121, with unit-cell parameters a = 6.7914 Å, b = 17.135 Å and c = 6.4360 Å, refining against 1364 independent reflections to an R1 of 0.092. The studied crystal proved to be an inversion twin, with domains in a 54:46 ratio. The resulting model matched the powder diffraction pattern well under Rietveld refinement, and the crystallographic data were deposited in the Inorganic Crystal Structure Database.

That structure is genuinely unique in mineralogy. It is layered on (010), built from two alternating types of sheets. One layer consists of vertex-sharing neodymium-centred polyhedra combined with carbonate groups lying flat in the layer. The other contains chains of strongly distorted, vertex-sharing sodium-centred octahedra running parallel to (100), flanked by carbonate groups standing on edge. Water molecules occupy three sites: one connects the sodium polyhedra into chains, while the other two tie the neodymium and sodium layers together through hydrogen bonds. Among the handful of known water-bearing carbonates dominated only by sodium and rare earth elements — thomasclarkite-(Y), shomiokite-(Y), lecoqite-(Y) and adamsite-(Y) — none shares this architecture. Adamsite-(Y) comes closest, with flat-lying and standing carbonate groups, but its layers are configured differently and its sodium layers are joined only by hydrogen bonds.

The deeper significance lies in why neodymium minerals are so scarce. Rare earth elements travel together in nature because of their similar chemistry, which is why the Levinson nomenclature system tags rare earth minerals with their dominant element in parentheses. Cerium, the largest of the light rare earths, boasts more than 160 minerals of its own, and yttrium nearly 140; neodymium, intermediate in size between cerium and yttrium, tends to disperse into both groups rather than concentrate. Only 37 neodymium-dominant minerals appear on the official IMA list as of April 2026, and those described from agpaitic complexes typically formed under highly specific local conditions that separated neodymium from its neighbours. Piilonenite-(Nd) follows a different pattern. Together with the recently described mckelveyite-group minerals bainbridgeite-(NdCe) from Mont Saint-Hilaire and mckelveyite-(Nd) from Russia’s Khibiny Massif, it shows a chemical affinity of neodymium for yttrium rather than cerium. The authors propose that in very late-stage hydrothermal fluids, as yttrium is depleted from solution, neodymium can become the prevalent rare earth element — allowing piilonenite-(Nd) and its kin to crystallise where cerium phases would normally dominate.

The mineral is named in honour of Paula Piilonen, a Canadian mineralogist at the Canadian Museum of Nature, former president of the Mineralogical Association of Canada and senior author of two earlier new-species descriptions from Mont Saint-Hilaire, with the suffix (Nd) following the Levinson convention. The holotype specimen, catalogue number CMNMC 93393, is preserved in the Canadian Museum of Nature collection in Ottawa. For a quarry that has already yielded dozens of first descriptions, piilonenite-(Nd) is a fitting addition — a mineral that spent a quarter of a century mistaken for something else, resisted four separate structural assaults, and finally surrendered its secrets to synchrotron light, revealing a crystal architecture no one had ever seen before.

Subject of Research: Description of the new neodymium-dominant carbonate mineral piilonenite-(Nd) from Mont Saint-Hilaire, Quebec

Article Title: Piilonenite-(Nd), NaNd(CO3)2 ⋅ 3H2O, a new neodymium-dominant carbonate mineral from Mont Saint-Hilaire, Quebec, Canada

Article References: Lykova, I., Rowe, R., Teat, S. J., Poirier, G., & Barnes, S. (2026). Piilonenite-(Nd), NaNd(CO 3 ) 2 ⋅ 3H 2 O, a new neodymium-dominant carbonate mineral from Mont Saint-Hilaire, Quebec, Canada. European Journal of Mineralogy, 38(3), 337-345. https://doi.org/10.5194/ejm-38-337-2026

Image Credits: AI Generated

DOI: 10.5194/ejm-38-337-2026

Keywords: piilonenite-(Nd), neodymium, new mineral species, Mont Saint-Hilaire, carbonate mineral, crystal structure, rare earth elements, agpaitic complex, synchrotron diffraction, Poudrette pegmatite, mineralogy, IMA approval

The study, led by Yuri Galliano of the University of Genoa together with colleagues from Genoa, Roma Tre and Bologna, was published in the European Journal of Mineralogy. The researchers combined three high-temperature, in situ analytical techniques with equilibrium thermodynamic calculations to pin down the transformation. Their target reaction is deceptively simple: taranakite, with the formula K3Al5(PO3OH)6(PO4)2·18H2O, loses six water molecules to become francoanellite, K3Al5(PO3OH)6(PO4)2·12H2O. Both minerals share the same layered architecture of aluminophosphate sheets, but taranakite carries additional water arranged in hexagonal interlayers that strikingly resemble the structure of ordinary ice. Francoanellite lacks these interlayers entirely, with hydrogen bonds directly connecting the layers in their place.

To predict the temperature at which this reaction reaches equilibrium, the team turned to the polyhedral approach, a modelling technique that estimates the bulk thermodynamic properties of a mineral by summing the contributions of its individual cation coordination polyhedra. Using published temperature-dependent functions for the Gibbs free energy of the constituent oxide and water units, they calculated an equilibrium transformation temperature of 369.12 kelvin, equivalent to about 96 degrees Celsius. That figure might seem far removed from the cool, damp interiors of caves, and indeed it is. The real story, as the experiments revealed, lies not in equilibrium thermodynamics but in the remarkably low kinetic barrier of the reaction.

The experimental evidence came from three complementary probes. High-temperature X-ray powder diffraction, performed at the University of Padua, tracked the long-range crystal structure as the sample was heated step by step from room temperature to 438 kelvin. Taranakite reflections remained stable up to about 358 kelvin, above which they steadily weakened while the peaks of francoanellite grew, until francoanellite stood alone at 398 kelvin. The basal spacing of the layered structure contracted from roughly 15.85 angstroms to 13.80 angstroms, a direct signature of the disappearing water interlayers. Rietveld refinement showed that taranakite’s unit cell expanded slightly through ordinary thermal expansion before dehydration began, while the francoanellite cell shrank slowly until the material collapsed into an X-ray amorphous state above about 418 kelvin.

Infrared spectroscopy added a molecular-level view of the water loss. The FTIR spectra of taranakite are a complex convolution of phosphate, hydrogen phosphate, ammonium, hydroxyl and water vibrational modes, and the researchers followed how each family of bands evolved with temperature. The integrated absorbance of the water bending and stretching regions decreased gently up to about 363 kelvin, then changed slope in a way compatible with the onset of francoanellite formation, before accelerating dramatically above roughly 403 kelvin as the remaining crystallisation water was expelled and the structure amorphised. Crucially, the spectra showed that the transformation begins with the breaking of weak hydrogen bonds that tether the interlayer water molecules to the aluminophosphate layers, the weakest links in the structural chain.

Micro-Raman spectroscopy proved to be the most sensitive witness of the phase change. The symmetric stretching vibration of the phosphate units appears near 952 wavenumbers in taranakite and shifts to about 933 wavenumbers in francoanellite, positions that can even be converted into precise phosphorus-oxygen bond lengths of 1.559 and 1.565 angstroms, matching the structural models beautifully. By fitting these two peaks in spectra collected during heating, the team could watch taranakite fade and francoanellite emerge in real time. Better still, by holding the sample at fixed temperatures of 353, 358, 363 and 373 kelvin and recording spectra every few minutes, they turned their spectrometer into a kinetic instrument, measuring how fast the transformation proceeds at each temperature.

From those isothermal runs, the researchers extracted the activation energy of the dehydration using several kinetic approaches, including Avrami and Austin-Rickett plots and a model-free method known as time to a given fraction. Within the temperature window where the reaction behaves consistently, the activation energy came out at just 7.6 plus or minus 0.7 kilojoules per mole. That is astonishingly low. Comparable dehydration reactions in variscite, montmorillonite clays and zeolites all demand more than 30 kilojoules per mole. The reason, the authors explain, is that the water molecules being released are not part of cation hydration shells but sit loosely in interlayers, bound by weak hydrogen bonds with long oxygen-oxygen distances. Once those bonds break, the transformation is essentially topotactic: the aluminophosphate layers survive intact and only new hydrogen bonds between layers need to form, keeping the energy barrier minimal. The slope values from the kinetic plots, all below one, suggest the reaction is diffusion-controlled, with water molecules escaping parallel to the layers along the interlayer channels.

These numbers solve a long-standing puzzle about francoanellite’s rarity and origin. Direct measurements inside actively decomposing guano mounds, such as those in Mulu Cave in Borneo, show temperatures seldom exceeding 30 degrees Celsius, far below the calculated equilibrium temperature of 96 degrees. But because the kinetic barrier is so small, only a modest temperature rise sustained over long periods is needed to push the reaction forward. The heat released by the exothermic microbial oxidation of organic matter in guano-admixed sediments, accumulating over tens to hundreds of years, is a plausible trigger. The researchers also note that anthropogenic heat sources, such as the powerful halogen spotlights used in tourist caves like Castellana in Apulia, where francoanellite was first discovered in 1976, could contribute. Alternative pathways, including direct precipitation from percolating solutions or dissolution-recrystallisation driven by humidity swings, remain possible but are now less necessary to invoke.

The study carries practical warnings as well as scientific insights. Taranakite transforms into francoanellite within tens of minutes at temperatures as low as 358 kelvin, conditions easily reached during routine sample preparation for X-ray diffraction, where heating is sometimes used to drive off environmental moisture. Curators and researchers handling phosphate-bearing cave samples must therefore take special care to avoid inadvertently dehydrating their specimens and destroying the very mineralogical record they hope to study. Beyond Earth, the work resonates with planetary science: hydrated sulfates and iron phosphates confirmed in the Martian regolith may have undergone similar dehydration histories, and understanding the thermodynamics and kinetics of such reactions could help reconstruct the hydrologic and atmospheric evolution of the red planet. For now, the humble guano piles of Italian caves have once again proven that even the smallest, strangest mineral archives can rewrite our understanding of how minerals live, change and die.

Subject of Research: Thermodynamics and kinetics of the dehydration transformation of guano-derived taranakite into francoanellite in cave environments

Article Title: Dehydration reactions in guano-derived minerals: the taranakite-to-francoanellite transformation

Article References: Galliano, Y., Campomenosi, N., Bellatreccia, F., Belmonte, D., De Waele, J., & Carbone, C. (2026). Dehydration reactions in guano-derived minerals: the taranakite-to-francoanellite transformation. European Journal of Mineralogy, 38(3), 353-372. https://doi.org/10.5194/ejm-38-353-2026

Image Credits: AI Generated

DOI: 10.5194/ejm-38-353-2026

Keywords: taranakite, francoanellite, bat guano, cave minerals, dehydration, phosphate minerals, X-ray diffraction, Raman spectroscopy, FTIR spectroscopy, thermodynamics, activation energy, mineralogy

The technique builds on a long tradition of sediment fingerprinting, the idea that every source area imprints a characteristic signature on the material it sheds. Researchers have traced sediment origins using geochemistry, radionuclides, isotopes, magnetic susceptibility, organic carbon, pollen, environmental DNA and even colour. The trouble is that many of these tracers are costly and slow to measure, which limits how widely they can be applied. X-ray diffraction, by contrast, is a workhorse technique: powdered samples are bombarded with X-rays, and constructive interference occurs only at specific angles determined by the spacing of atomic planes in the crystals present. The resulting diffraction pattern is a mineralogical fingerprint that can be collected quickly and cheaply for large numbers of samples.

The team’s workflow transforms raw diffractograms into usable fingerprints through a series of processing steps. Baseline drift is corrected and background noise removed with a peak-finding algorithm, and the patterns are aligned to a pure quartz reference to eliminate instrumental misalignments. Diagnostic two-theta windows for each target mineral are selected from reference spectra in the RRUFF database, and the total peak area within each window is averaged and normalised, yielding relative mineral concentrations on a scale from zero to one. Crucially, averaging peak areas across a window rather than relying on individual peaks mitigates the overlap that occurs when different minerals diffract at similar angles. The researchers focused on 21 primary rock-forming minerals, from quartz and feldspars to pyroxenes, amphiboles, micas and garnet, deliberately excluding the clay minerals produced by chemical weathering.

Turning fingerprints into erosion rates requires an inversion. The forward model is conceptually straightforward: each source area, typically a geological unit, carries its own mineral signature, erodes at some rate, and contributes sediment in proportion to that rate. The mineral concentrations measured in suspended sediment downstream are therefore a weighted average of the source signatures, with the weights being the erosion rates. Because erosion rates must be positive, the team solved the problem in log-space, making the mixing model non-linear. The inverse problem is underdetermined, since the number of tracers is far smaller than the number of pixels for which erosion rates are desired, so many different maps could explain the same data.

To tame this ambiguity, the authors adopted a Bayesian maximum a posteriori approach. They sought the most probable erosion map given the observed detrital data and prior knowledge encoded in a model covariance that favours spatially smooth solutions, with the smoothing distance and prior variance acting as tunable hyperparameters. Two iterative optimisation schemes were tested: steepest descent and a quasi-Newton method that uses curvature information to accelerate convergence. In synthetic forward-inverse tests, the quasi-Newton approach reconstructed a known erosion pattern with a localised hotspot far more accurately, while the steepest descent scheme proved unstable unless its gradient was normalised, which smoothed out sharp features and required many more iterations. The quasi-Newton method was therefore adopted for all subsequent experiments.

The sensitivity tests revealed which ingredients matter most. When the researchers progressively blended the source fingerprints together, making different lithologies mineralogically similar, the inversion deteriorated sharply: once a similarity metric called the average Jensen-Shannon distance fell below about 0.55, both errors and posterior uncertainty rose steeply, and in the most blended cases the inversion failed to converge at all. Uncertainty in the geological map, relevant in glaciated terrain where bedrock cannot be directly observed, was the second most influential factor. Reducing the number of tracer minerals had comparatively little effect, provided the most informative ones were retained: seven tracers produced essentially the same posterior solution as the full set of 21. Parameter sweeps showed the method is robust across a wide range of smoothing distances, standard deviations and step sizes, with convergence essentially complete after roughly 115 iterations.

The real-world validation took place in the Gornergletscher catchment in the Swiss Alps, an ideal testing ground because it combines multi-year suspended sediment records with strongly heterogeneous bedrock. The catchment drains lithologies from both oceanic and continental domains of the Pennine Alps, including serpentinites and eclogites of the Zermatt-Saas Fee ophiolites, calcareous mica schists and quartzites of the Penninic Mesozoic sediments, and the granites and garnet-mica schists of the Monte Rosa nappe. The XRD fingerprints derived from bedrock samples aligned well with established geological knowledge of these units, confirming that the cleaning and binning procedure preserves meaningful mineralogical information.

Two natural experiments put the method through its paces. In the first, the team exploited a natural analogue of a known-mixture test: sediment collected at the Gorner-Grenzgletscher confluence, where a subcatchment drains only part of the full study area. When the inversion was run using the geology of the entire catchment, it correctly attributed erosion only to lithologies actually present within the subcatchment, predicting rates close to zero for the Zermatt-Saas Fee sediment unit, which has no outcrops there. In the second, the XRD approach was benchmarked against zircon U-Pb age fingerprinting on the same detrital sample. The zircon-only inversion was highly unstable, producing implausible erosion rates above 8000 millimetres per year and high uncertainty, partly because two lithological units lacked zircon data altogether. The XRD-based solution was markedly more stable, and concatenating both datasets improved the distinguishability of source fingerprints and stabilised the posterior further, suggesting the two tracers are complementary rather than competing.

The authors are careful about the method’s limits. Grain-size effects, mineral fractionation during transport and post-depositional alteration can all bias fingerprinting, but several lines of evidence suggest these are modest in the Gorner setting: the suspended load is dominated by silt-sized glacial flour produced by physical comminution, only primary rock-forming minerals were used as tracers, and pump samples and depth-integrated samples yielded nearly identical mineralogies. The inversion also assumes that sediment is exported promptly rather than stored, so catchments with large sediment reservoirs are poor candidates. With those caveats, the recipe is appealingly simple: binned XRD data from sediments and source rocks, a map of potential source areas, and an estimate of total annual suspended sediment export. Because XRD is fast and affordable, the approach could open up provenance analysis to far more catchments, and the framework is flexible enough to accept other tracers, from zircon ages to geochemistry, or source maps based on land use rather than geology. For glacierised basins, where ice conceals the very landscapes doing the eroding, a cheap X-ray scan of river mud may now be enough to reveal where the ground is giving way.

Subject of Research: X-ray diffraction sediment fingerprinting and non-linear inversion to map erosion rates in glacierised catchments

Article Title: From XRD signal to erosion rate maps

Article References: De Doncker, F., Herman, F., Belotti, B., & Adatte, T. (2026). From XRD signal to erosion rate maps. Earth Surface Dynamics, 14(3), 443-467. https://doi.org/10.5194/esurf-14-443-2026

Image Credits: AI Generated

DOI: 10.5194/esurf-14-443-2026

Keywords: sediment fingerprinting, X-ray diffraction, erosion rates, provenance analysis, Bayesian inversion, glaciers, Gornergletscher, suspended sediment, mineralogy, Swiss Alps, Earth Surface Dynamics, inverse problems

Bainbridgeite-(NdCe) has the ideal chemical formula Na2Ba2NdCe(CO3)6·3H2O, meaning that each unit of the mineral combines two sodium atoms, two barium atoms, one neodymium atom, one cerium atom, six carbonate groups, and three water molecules. It belongs to the mckelveyite group, a family of rare hydrated carbonates whose general formula can be written as A3B3(CO3)6·3H2O, where the A sites are occupied by elements such as sodium, calcium, yttrium, zirconium, and neodymium, while the B sites host strontium, barium, cerium, and lanthanum. The new species is the neodymium analogue of bainbridgeite-(YCe), which was described from the same locality in 2024, and it is also the barium-neodymium analogue of alicewilsonite-(YCe). Both the mineral and its name were approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association under proposal number IMA 2023-018, and the holotype specimen has been deposited in the collection of the Canadian Museum of Nature in Ottawa under catalogue number CMNMC 90534.

The mineral was found at the Poudrette quarry, a site within the Mont Saint-Hilaire alkaline and agpaitic complex that has produced an extraordinary number of new mineral species over the decades. Bainbridgeite-(NdCe) turned up in two quite different geological settings. The first is an environment referred to in the literature as carbonate pegmatites or carbonate vugs, bodies rich in calcite that lack the pyroxene and amphibole minerals typical of alkaline pegmatites and whose origin remains poorly understood. In this setting, the type material was recovered from a heavily altered body consisting mostly of calcite and albite, collected by Elsa Pfenninger-Horváth and László Horváth in February 1978. There, bainbridgeite-(NdCe) forms thin rims, up to twenty to thirty micrometers thick, on barrel-shaped short prismatic crystals reaching two millimeters in size. Remarkably, the cores of those same crystals are composed of bainbridgeite-(YCe), with an intermediate zone corresponding to a member of the bainbridgeite-(YCe)-alicewilsonite-(YCe) series, so a single crystal records a sequence of changing chemical conditions during its growth.

The second occurrence is quite different. In a hornfels rock, bainbridgeite-(NdCe) appears as white or pale-grey tabular, saucer-shaped crystals up to half a millimeter across, commonly stacked together and associated with yellow acicular rutile, colourless hexagonal tabular gmelinite-Na, sphalerite, calcite, analcime, and pyrite. In these crystals, the entire grain is bainbridgeite-(NdCe), with no yttrium-dominant core. The coexistence of the mineral in both a carbonate-rich vug environment and a hornfels highlights the versatility of late-stage fluids in the Mont Saint-Hilaire complex, which apparently could deliver the right combination of sodium, barium, carbonate, and rare-earth elements in more than one geological context.

Physically, bainbridgeite-(NdCe) is a pale yellow, pale orange, white, or pale grey mineral with a white streak and a vitreous lustre. It shows no cleavage, has an uneven fracture, and a Mohs hardness of three, determined on material from the hornfels occurrence because the rims in the holotype are too thin for such a test. The mineral is non-fluorescent under ultraviolet light, and its calculated density is 3.49 grams per cubic centimeter. Optically it is biaxial positive, with refractive indices of 1.577, 1.592, and 1.657 for the three principal axes, and a measured axial angle of forty degrees. These modest, unassuming properties are typical of the mckelveyite group, whose members are usually recognized not by striking appearance but by careful chemical and crystallographic analysis.

Characterizing the new species demanded a battery of analytical techniques, and the researchers had to contend with some serious practical obstacles. Electron microprobe analyses were performed with a JEOL 8230 SuperProbe using wavelength-dispersive spectroscopy, but bainbridgeite-(NdCe) is unstable under the electron beam, so larger beam diameters of ten to twenty micrometers were used to minimize element migration, and time-dependent intensity corrections were applied for several elements. Water and carbon dioxide contents could not be measured directly because of the scarcity of material and were instead calculated from stoichiometry. Infrared spectroscopy, carried out at the Canadian Conservation Institute on a tiny fragment mounted in a diamond anvil cell, confirmed the presence of water molecules through characteristic oxygen-hydrogen stretching and hydrogen-oxygen-hydrogen bending bands, and revealed a band at 1064 wavenumbers indicating that the carbonate groups in the structure are polarized rather than symmetric.

X-ray diffraction work proved equally challenging. Powder diffraction data could not be collected from pure bainbridgeite-(NdCe), because not enough separate grains could be recovered, so the measured pattern represents an average of the new mineral and its yttrium-dominant neighbour. Single-crystal diffraction, performed at the Natural History Museum in Oslo on a Rigaku XtaLAB Synergy-S diffractometer, faced the same problem: because bainbridgeite-(NdCe) occurs only as a thin rim on bainbridgeite-(YCe) and the boundary between the two phases is not visually identifiable, the structural model represents an average of both phases. Even so, the structure was solved and refined to an R1 value of 0.036 in the triclinic space group P1, with unit-cell parameters a of 9.0525 angstroms, b of 9.1178 angstroms, c of 6.8518 angstroms, and a cell volume of 438.23 cubic angstroms. The structure is of the weloganite type and is strongly pseudotrigonal, with six independent large-cation sites forming two alternating layers parallel to the ab plane, three water molecules bonded to barium- and sodium-centred polyhedra, and six carbonate groups, three of which lie nearly coplanar with the (001) plane.

The heart of the discovery lies in the distribution of cations among those sites. By combining electron microprobe data, refined site-scattering factors from the diffraction experiment, interatomic distances, bond valence calculations, and charge balance, the team demonstrated that neodymium atoms overwhelmingly prefer the site designated Nd6, while cerium atoms concentrate at the Ce3 site. The evidence is compelling from chemistry alone: the neodymium content of the holotype, 0.35 atoms per formula unit, is significantly higher than that of any single heavier lanthanide, higher than the combined total of all heavier lanthanides from samarium through dysprosium, higher than the yttrium content, and far higher than the neodymium content of the yttrium-dominant holotype of bainbridgeite-(YCe). A specimen from the hornfels shows an even stronger pattern, with 0.41 atoms of neodymium per formula unit. Structural evidence reinforces the case: the site occupied predominantly by yttrium in bainbridgeite-(YCe) is instead dominated by neodymium and other lanthanides in the new mineral, consistent with a substitution of yttrium by rare-earth elements at that position.

Why does neodymium, an element that usually disperses among other rare-earth-bearing minerals rather than forming its own phases, concentrate here? The authors propose a mechanism rooted in crystal chemistry. Neodymium has a particular affinity for yttrium, and in late-stage agpaitic environments, as yttrium becomes depleted from the residual fluid, neodymium can rise to become the dominant rare-earth element in a newly forming phase. The team previously demonstrated this behaviour in piilonenite-(Nd), another neodymium-dominant carbonate from Mont Saint-Hilaire. The model makes a testable prediction: samarium and gadolinium, which are smaller than neodymium but larger than the heavy rare earths that typically follow yttrium, should show an even greater affinity for yttrium-favouring sites and should therefore also become enriched in late-stage phases. The chemical data bear this out. Samarium and gadolinium contents rise from negligible values of 0.01 and 0.03 atoms per formula unit in the yttrium-dominant cores of the crystals to 0.18 and 0.14 atoms per formula unit in the neodymium-dominant rims, with similar enrichment in the hornfels material.

Bainbridgeite-(NdCe) thus does more than add a name to the mineralogical record. It provides a natural experiment in element sorting, showing how the subtle size preferences of individual rare-earth atoms can drive their separation into distinct structural sites as a magmatic system evolves. Because rare-earth elements underpin modern technologies from permanent magnets to phosphors, understanding the crystallochemical rules that govern their partitioning in alkaline complexes has relevance well beyond mineral taxonomy. Mont Saint-Hilaire, which has yielded dozens of new species since quarrying began, once again demonstrates its unmatched ability to preserve the chemistry of late-stage fluids in exquisitely rare and structurally intricate minerals, and the mckelveyite group, now spanning five formally described parts, continues to reveal how nature organizes some of the rarest elements in the crust.

Subject of Research: Crystal chemistry and site-specific rare-earth element partitioning in a new mckelveyite-group carbonate mineral

Article Title: Mckelveyite group minerals – Part 5: Bainbridgeite-(NdCe), Na2Ba2NdCe(CO3)6●3H2O, a new neodymium and cerium-dominant species from Mont Saint-Hilaire, Canada

Article References: Lykova, I., Rowe, R., Poirier, G., Friis, H., Ojaste, K., & Barnes, S. (2026). Mckelveyite group minerals – Part 5: Bainbridgeite-(NdCe), Na 2 Ba 2 NdCe(CO 3 ) 6 ●3H 2 O, a new neodymium and cerium-dominant species from Mont Saint-Hilaire, Canada. European Journal of Mineralogy, 38(4), 419-429. https://doi.org/10.5194/ejm-38-419-2026

Image Credits: AI Generated

DOI: 10.5194/ejm-38-419-2026

Keywords: bainbridgeite-(NdCe), new mineral species, Mont Saint-Hilaire, mckelveyite group, rare-earth elements, neodymium, cerium, carbonate mineral, crystal structure, X-ray diffraction, alkaline complex, mineralogy

The mineral was approved by the International Mineralogical Association’s Commission on New Minerals, Nomenclature and Classification under proposal number IMA 2024-091, and carries the official symbol Xhu-Ce. Its name honors Professor Xianhua Li, an academician of the Chinese Academy of Sciences, in recognition of his contributions to research on early Earth and planetary evolution and, in particular, his recent advances in the geochronology, geochemistry, and resource development of the Bayan Obo deposit. The holotype specimen, catalogued as GMCTM2024012, is held at the Geological Museum of China in Beijing, while a co-type specimen resides in the crystal structure laboratory at China University of Geosciences, Beijing. These reference samples ensure that any future researcher can compare material against the defining specimens of the species.

Xianhuaite-(Ce) was found in two rock samples collected from different parts of the Bayan Obo complex. One specimen, BY-E2024-103, came from the East Orebody, where it occurs as black-brown megacrystalline aggregates at the contact between aegirine-type and dolomite-type niobium-rare earth-iron ores. The other, BY-EC2024-14, was collected from the East Contact Zone within dolomite-type ore. In that second sample, quantitative mineral mapping using a Tescan integrated mineral analyzer showed the rock is dominated by dolomite at nearly 72 percent by volume and magnetite at about 12 percent, with fersmite making up 8 percent. Xianhuaite-(Ce) itself accounts for a modest 0.40 volume percent, appearing alongside columbite-(Fe), aeschynite, fergusonite-(Ce), and small amounts of pyrochlore, phlogopite, barite, apatite, and other phases typical of skarn-altered assemblages.

Under the microscope and in hand specimen, the new mineral presents as irregular grains or tetragonal prisms ranging from tiny slivers of roughly 0.03 by 0.03 by 0.1 millimeters up to crystals of about 0.4 by 0.4 by 0.6 millimeters. It is dark brown to blackish brown in bulk, but thin fragments transmit a pale yellow-brown to brownish-red light. It shows an adamantine luster, a white streak, perfect cleavage on the {001} plane, and a conchoidal fracture, and it is brittle. Its Mohs hardness falls between 5 and 6, and micro-indentation testing yielded a mean Vickers hardness number of 469.5 kilograms per square millimeter at a 200-gram load. The calculated density is 5.23 grams per cubic centimeter, and the mineral shows no fluorescence under longwave ultraviolet light and no magnetic response.

Chemical analysis by electron probe microanalysis with wavelength-dispersive spectrometry, performed on a JXA-iHP200F instrument at 15 kilovolts and 20 nanoamperes, established the empirical formula. Normalized to 15 oxygen atoms per formula unit, it reads (K1.30Ba0.69Sr0.02)(Ce0.39La0.31Nd0.04Pr0.02Ca0.15Na0.09)(Nb4.75Fe0.13Ti0.09Mg0.04)O15. In plain terms, the large channel sites of the structure are filled mostly by potassium and barium, with a smaller site occupied chiefly by cerium and lanthanum plus minor calcium and sodium, while the octahedral framework sites are dominated by niobium with a little iron, titanium, and magnesium. Backscattered electron imaging confirmed the crystals are chemically homogeneous at the micrometer scale, and the simplified formula (K,Ba)2(Ce,La)(Nb,Fe)5O15 rounds to the ideal K2CeNb5O15.

The structural work is where the discovery becomes remarkable. Single-crystal X-ray diffraction on a fragment measuring just 0.02 by 0.02 by 0.01 millimeters, collected with molybdenum radiation on a Rigaku XtaLAB PRO-007HF diffractometer, revealed a tetragonal unit cell with a = 12.5355 angstroms, c = 3.9213 angstroms, and a volume of 616.19 cubic angstroms, in the centrosymmetric space group P4/mbm. The refinement converged to an R1 value of 0.0189 based on 427 independent reflections, an exceptionally good fit. The structure is a textbook tetragonal tungsten bronze framework: niobium-centered oxygen octahedra share corners to build a two-dimensional network in the horizontal plane, generating rings of four and five octahedra that line vertical channels running along the c axis. The larger five-membered channels host potassium and barium in ninefold coordination, while the four-membered channels accommodate cerium and calcium in twelvefold coordination.

Raman spectroscopy independently corroborated this architecture. The spectrum shows a prominent band near 853 wavenumbers assigned to vibrations of the NbO6 octahedra, additional peaks at 645 and 537 wavenumbers corresponding to niobium-oxygen stretching modes, and low-frequency features at 175, 135, and 81 wavenumbers characteristic of cation motions in tetragonal tungsten bronze phases. The absence of any peaks above 1000 wavenumbers is consistent with a structure containing no hydroxyl or water groups. Bond valence sum calculations further confirmed that the assigned oxidation states and site occupancies are internally consistent, with the B1 octahedral site modeled as roughly 95 percent niobium and 5 percent trivalent iron, matching the chemical analyses.

What does the mineral say about how Bayan Obo formed its enormous metal endowment? The deposit has been studied for decades, yet the mechanisms of niobium enrichment remain debated, largely because the niobium is scattered across at least 30 distinct mineral species rather than locked in one dominant host. The textural evidence from the East Contact Zone sample offers a clue: xianhuaite-(Ce), fersmite, and columbite-(Fe) occur as interstitial phases between magnetite grains, and both xianhuaite-(Ce) and fersmite contain relict pyrochlore inclusions inherited from an earlier mineralization stage. The authors argue these relationships are inconsistent with primary magmatic crystallization and instead point to precipitation from niobium-bearing fluids during a later hydrothermal overprint. The surrounding assemblage of forsterite, phlogopite, chlorite, and dolomite is characteristic of magnesian skarn systems formed when granite intrudes dolomitic host rocks.

The regional context strengthens that interpretation. The East Contact Zone experienced variable degrees of skarnization during the emplacement of Permian granites, a thermal event that apparently did not add new niobium to the system but likely remobilized niobium already present. Taken together, the mineral assemblages, textures, and geology suggest xianhuaite-(Ce) formed under fluid-dominated conditions during the Permian granitic event, recording the remobilization and redistribution of niobium rather than its original accumulation. The coarse-grained East Orebody sample lacks diagnostic assemblages for direct petrographic constraints, but regional geochronology indicates the Permian thermal event affected the entire district, so the researchers tentatively assign its xianhuaite-(Ce) to the same episode, while noting that direct dating is still lacking.

The discovery also resonates beyond geology. Synthetic compounds with the same ideal composition, K2CeNb5O15, belong to a family of tetragonal tungsten bronze materials studied for their physical properties, and laboratory work has documented temperature-driven symmetry transitions within this structural family. The natural mineral refines best in the centrosymmetric high-temperature form, P4/mbm, and intensity statistics support that choice. By capturing a structure long known only from synthesis, xianhuaite-(Ce) expands the known structural diversity of natural niobium minerals and provides new mineralogical constraints on how niobium behaves during the multistage evolution of one of the world’s most extraordinary ore deposits. For a metal critical to advanced technologies, every new clue about where and how it concentrates carries practical weight.

Subject of Research: Discovery and characterization of the new niobium mineral xianhuaite-(Ce) from the Bayan Obo deposit

Article Title: Xianhuaite-(Ce), K2CeNb5O15, a new niobium mineral from the Bayan Obo deposit, China

Article References: Yang, B., Xue, Y., Yang, L., Sun, N., Li, G., Yu, J., Yan, G., Liu, J., Zhao, Y., Meng, W., Chen, Z., Chen, L., Liu, Z., Yan, Z., Hou, X., Ao, X., & Wang, J. (2026). Xianhuaite-(Ce), K 2 CeNb 5 O 15 , a new niobium mineral from the Bayan Obo deposit, China. European Journal of Mineralogy, 38(4), 449-459. https://doi.org/10.5194/ejm-38-449-2026

Image Credits: AI Generated

DOI: 10.5194/ejm-38-449-2026

Keywords: xianhuaite-(Ce), Bayan Obo, niobium, new mineral, tetragonal tungsten bronze, rare earth elements, crystal structure, skarn, hydrothermal remobilization, mineralogy, Inner Mongolia, electron microprobe