This study explains how scientists determine whether a newly found solid phase is truly a natural mineral. We refine existing guidelines by introducing updated recommendations that improve the credibility of proposals for minerals with uncertain origins. Using three examples, we show how geological and textural evidence can confirm or challenge natural authenticity. Our new checklist helps reduce misinterpretation and ensures more reliable mineral recognition.

The Ertelien and Langedalen Ni–Cu sulfide deposits are hosted in gabbronorite intrusions formed in a convergent margin. The Ertelien deposit contains contact-related sulfides, whereas the Langedalen deposit hosts massive sulfides within extensively deformed gabbronorite lenses. Both are depleted in platinum-group elements (PGEs), which could be related to a metasomatized pyroxenitic mantle source. Isotopic data support a subduction-related origin around 1550 Ma, with magmatic signatures preserved despite later alteration.

Kayupovaite is a new mineral named in honor of Maria Mikhailovna Kayupova (1921–1980), the mineralogist who studied the Ushkatyn-III deposit (Kazakhstan), the type of locality of the described mineral. Kayupovaite is monoclinic and of space group C2/c. The mineral belongs to the group of modulated manganese phyllosilicates and is structurally related to stilpnomelane. The absence of iron in the mineral is a result of oxidative Mn–Fe fractionation during the formation of braunite-rich Mn ores.

The paper describes an analysis of the crystal structures of the minerals of the triphylite, alluaudite, zwieselite, and graftonite groups, from the perspective of the ubiquitous presence of 2-polyhedra-wide ribbons formed from corner linking of M₂(PO₄)₂Φ₈ cyclic tetramers. The study helps to unify the crystal chemistry of the four most dominant primary Fe and Mn phosphate mineral groups in granitic pegmatites.

The two most recent eruptive events of Nisyros volcano (Greece) record the interaction between variably evolved magmas by the presence of mafic enclaves, indicative of multiple recharge events within the magma chamber. We use the mineral chemistry composition to constrain the location of the main eruptible reservoirs and their evolution at the transition from explosive to effusive activities, with implications for magma migration and storage in the crust.

During project STARDUST, over 5500 specimens were recovered. Among them, a micrometeorite from Oslo (NMM/L2) revealed a new Al–Cu alloy with Al₄Cu₉ stoichiometry. This phase was approved as a new mineral named jonlarsenite. The microspherule shows features typical of micrometeorites. Its extraterrestrial origin is confirmed by oxygen isotope composition and chondritic chemistry, similar to previously known Al–Cu meteoritic materials.

Calcium silicate perovskite (Ca-pv) is the third most abundant mineral in Earth's interior. Knowledge of its elasticity is significant for deciphering the origins of seismic signatures. Elasticities and sound velocities of Ca-pv have been theoretically investigated. Compositional effects on elastic properties and velocity anisotropies of Ca-pv are significant at lower-mantle pressures. Ca-pv may be related to the observed seismic anomalies associated with subducted oceanic crust in the lower mantle.

Suenoite is a new Pnma amphibole discovered in the Mn ore deposit of Scortico–Ravazzone, Apuan Alps, Tuscany, Italy. Its discovery adds further complexity to the amphibole supergroup, and it represents the first Pnma amphibole with ^BMn²⁺.

A suite of clinopyroxenes from ankaramitic magmas of the Miocene Teno massif and Roque del Conde shield volcanoes (Tenerife, Canary Islands) were studied to obtain geothermobarometric information on the anatomy of the volcano plumbing system.

Marioantofilliite, ideally [Cu₄Al₂(OH)₁₂](CO₃)•3H₂O, is a new member of the hydrotalcite supergroup occurring as a supergene mineral in the Cu–Fe deposit of Monte Copello–Reppia (Liguria, Italy). Its name honours Mario Antofilli (1920–1983) for his contribution to the knowledge of the mineralogy of Liguria. Its discovery and description improve the knowledge of layered double hydroxides (LD), with implications for the group of Cu–Al LDH actively studied for its technological properties. 

Seventeen tourmalines from Brazil were investigated by structural and chemical techniques. Most samples are Na-dominant and belong to the alkali group. They correspond to fluor-elbaites or elbaites, except one sample, which corresponds to a rossmanite. Structural data indicate that the B site is fully occupied by boron, that the T site is occupied by Si, and that the Z site is mainly occupied by Al. The X site contains vacancies, Na, K, and Ca, and the Y site is mainly occupied by Li, Al, and Fe²⁺.

Single-crystal X-ray diffraction has been used to characterise the structural properties of a CaIrO₃ orthorhombic perovskite-type structure under ambient and high pressures. It has been found that the structure of this compound is more distorted than other CaO perovskites. Structural determination at high pressure also shows a peculiar compression behaviour that is different from the other CaO perovskites. This explains why this material is much stiffer than expected.

Zircon in highly differentiated systems such as rare-metal granites often exhibits unusual texture and composition that need to be clarified. Based on a detailed study on zircon from the Beauvoir rare-metal granite (France), we show that zircon crystals were partially replaced during the magmatic–hydrothermal transition of these systems, resulting in a significant change in their crystal texture and chemistry.

The Léon region in France offers a window into the dramatic geological processes that shaped continents. Studying ancient rocks called eclogite, we uncovered a history of magma generation, deep burial and rapid crustal movement between 390 million and 300 million years ago. The area was shaped by subduction dynamics, where shifting tectonic plates stretched and compressed the crust. These findings help us understand how ancient geological processes continue to influence the Earth’s surface today.

A new rare-earth-bearing silicate is described from a manganese ore deposit in the Pyrenees. It belongs to the epidote family and is characterised by the formula Mn²⁺Ce(MgAlMn²⁺)(Si₂O₇)(SiO₄)F(OH).  This new mineral commonly contains inclusions of an Mn-rich yttrium borosilicate, a potentially new mineral of the hellandite family. This is a new type of occurrence for hellandite – while rare earths are under the spotlight.

Chromites found within the fusion crust of ordinary-chondrite meteorites display significant differences with respect to chromites found in the interior of the same meteorites. Chromites within the fusion crust, when compared to those in the interior of the meteorite, display a significantly higher Mg / (Mg + Fe) ratio; moreover, ca. 15 % of the chromites formed within the crust display small but detectable amounts of Ni.

We conducted this research to gain understanding of the mineral rouxelite, which contains elements like antimony, copper, mercury, and lead. Using advanced X-ray techniques, we re-examined its crystal structure and discovered new details, such as unit-cell parameters, symmetry, and substitutions. These findings provide accurate information about how the mineral forms and behaves. This work not only updates scientific knowledge of rouxelite but also offers insights into its chemical complexity.

This study investigates the order–disorder phase transition in ankerite samples that vary in Fe content within their crystal structure. Results indicate that both the temperature and the character of the order–disorder phase transition are significantly influenced by the amount of Fe in the mineral's crystal structure. The obtained results might have significant implications for ankerite mineral physics under non-ambient conditions and significance in geophysical modeling of the Earth's mantle.

Natrolitised Early Cretaceous metaplutonites (melteigites, ijolites) contain various accessory minerals. The natrolitisation was a very low-temperature process, which did not affect most of the primary minerals, including most of the accessories. The evidence shows the release of barium and strontium, possibly from feldspathoids, from primary Na–Ca feldspars, and optionally also from glass, during the natrolitisation.

The thermal reaction Fe²⁺ + OH^- → Fe³⁺ + O^2- + e^- + H⁺ in hydrous silicates has tremendous implications in planetary-scale phenomena like electrical anomalies, water cycling, seismicity, volcanism, and ore generation. We annealed riebeckite crystals up to 750 °C and P = 0.7 GPa and show that the amphibole stability is extended without any Fe oxidation, implying that thermally activated electron hopping contributes to the electrical conductivity of lithospheric rocks during subduction.