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.

A thorough multimethod characterisation of the green dolomite sampled at the Malentrata magnesite mine has been carried out. We observed (1) a peculiar reduction of the cell volume and (2) the origin of the peculiar green colour, mainly determined by the Fe electronic transitions, probably in combination with those of Cr. In fact, the green dolomite of Malentrata contains aliquots of a number of environmentally relevant elements, in particular Mn, Cr, and Ni.

This study describes the elbaite neotype, found in crystals from a site on Elba island, Italy. Researchers analyzed these nearly colorless crystals and found that their formation was influenced by earlier changes in the surrounding rock. As different minerals formed first, they set the stage for elbaite to develop later in deeper spaces. This work helps us understand how changes in the local environment affect how and when certain minerals grow.

In this work, we present the most iron-rich chrysoberyl discovered to date, found in the Sabatini Volcanic Complex (Latium, Italy). We provide a comprehensive overview of its chemical, structural, spectroscopic, and optical properties. The characterization of this chrysoberyl reveals several unique features, offering valuable insights into its genetic model and geochemical constraints, which are consistent with existing literature on the Sabatini complex and with ongoing research.

Garnet crystals record the evolution of the pressure–temperature conditions during their growth. Thermodynamic modelling and the presence of coesite inclusions testifies that these rocks equilibrated along a pressure–temperature path crossing the equilibrium between quartz and coesite. This allows for discussing the role of energetic barriers during crystal growth. This was found insignificant, except for rocks that contain previous garnet crystals that have difficulties to achieve equilibrium.

An unusual tourmaline was studied using a multi-analytical approach. The sample comes from a granitic pegmatite on the island of Elba and consists of three generations of tourmaline: green prismatic tourmaline, a dark fibrous cap, and colourless acicular single crystals. The most likely scenario for its formation involves the miarolitic cavity fracturing due to mechanical shock, the subsequent circulation of the highly reactive cavity fluids, and the leaching of accessory biotite in the surrounding pegmatite.

As magma ascends, H₂O-supersaturated melt forms fluid vesicles, creating high vesicle number densities (VNDs) and increasing melt porosity, accelerating magma ascent. This study examines how VNDs vary with decompression rate as vesicles begin to coalesce. The shift from decompression-rate-independent to decompression-rate-dependent VND can strongly influence eruption styles, creating permeable channels or forming closed-porosity foams that trap pressurized gas, potentially leading to explosive eruptions.

We provide new insights into the release of H₂O from the phonolitic melt of the Laacher See volcano. Decompression experiments conducted at superliquidus conditions revealed uniformly dispersed vesicles throughout the samples, with extremely high vesicle numbers regardless of the decompression rate. These findings enhance our understanding of volcanic eruptions and might suggest that rapid volatile release due to off-critical spinodal decomposition increases explosive volcanic activity.

Understanding the chemical evolution of the earth's mantle is important in the cycling of elements through the earth system. This work shows how mantle that has previously been partially melted can be re-enriched by carbonate-rich and silicate magmas. Samples of the mantle collected from volcanic rocks in the Eifel volcanic field and the mineral clinopyroxene were analyzed to reveal its chemical signatures, which were used to determine the nature of the processes that affected the Eifel mantle.

This paper reports a new natural oxyphosphate, the first mineral that crystallizes in the α-Fe₂PO₅ structure type. It is isotypic to a series of synthetic oxyphosphates with promising magnetic and electrochemical properties.

The purpose of this paper is to present new perspectives on the pressure estimate of submicrometric white mica using energy-dispersive X-ray spectroscopy performed by a transmission electron microscope. This technique aims to explore the mineral chemistry of single grains whose dimensions do not allow for analysis by microprobe. The validation of this procedure opens a wide range of applications hitherto untested due to instrumental incompatibility with mineral phases smaller than 5 µm.

Ginelfite is a new Ag–Fe–Tl–Pb sulfosalt described from the hydrothermal deposit of Jas Roux (France). It belongs to the so-called boxwork sulfosalts, a group of species showing the highest structural complexity among this group of chalcogenides. This very complex structure is probably stabilized by the occurrence of minor chemical constituents (Tl, Fe) occupying specific structural positions. 

To understand the hydrosphere's internal cycle, we need to study the isotopic composition of hydrogen in the Earth's depths. We present a multidisciplinary approach to quantify the ratio of deuterium vs. hydrogen in nominally anhydrous minerals like olivine and its high-pressure polymorph wadsleyite. This study is a prerequisite for the determination of how heavy and light isotopes of hydrogen distribute among the different minerals hosting hydrogen in the mantle.

This review collects the most significant research on metal-based minerals in the brain, their relationship with neurological disorders, and their relationship with urban pollution. This review emphasizes the importance of medical mineralogy in investigating the effects of these minerals. Future research should focus on mineralogical characterization, evolution, and nanoscale to atomic-scale characterization of metal-based particles.

Skogbyite, with the chemical formula Zr(Mg²⁺₂Mn³⁺₄)SiO₁₂, is a new species in the braunite group of minerals. It was discovered in a complex mineral assemblage, essentially a very poor manganese ore, from the Långban Fe–Mn oxide deposit, Värmland County, Bergslagen ore province, Sweden. It is named after the Swedish mineralogist Henrik Skogby (b. 1956). It is a new mineral attesting to the localised mobility and reactivity of zirconium under very special geological conditions.