Recent  

Bobtraillite is an extremely rare cyclosilicate with a unique composition and complex structure. In this paper, we describe the second occurrence of the extremely rare complex zirconium silicate. The results suggest that the ideal formula of bobtraillite could be written as (Na, □)₁₂(□, Na)₁₂Sr₁₂Zr₁₄(Si₃O₉)₁₀[Si₂BO₇(OH)₂]₆·12H₂O.

When detecting the light element boron in solid materials with, in part, considerably lower concentrations of boron than present in natural tourmalines by using the electron microprobe, irregularities become visible in the analyses. This was for the first time experienced in synthetic diamond that was contaminated with boron to achieve a blue color. With this work, one can check if boron analyses are reasonable, and if not, one can correct them.

Using neural networks with experimental data, we infer the relationship between pressure, temperature and shear properties of MgO. Fixing the form of the relationship, which is a common practice, provides the properties that are largely constrained by the form and not the data. Our approach provides realistic uncertainties in shear properties, which should improve uncertainty quantification in interpretations of observed shear wave speed to infer the structure and dynamics of the Earth’s mantle.

Members of the epidote supergroup, epidote, clinozoisite, allanite, and ferriallanite, are described from the calcium–aluminum silicate and thermometamorphic zones in drill cores obtained from the Mofete and San Vito wells in the Campi Flegrei (Italy) geothermal field. Compositional zoning is ubiquitous. The epidote group encompasses nearly the complete range of coupled Al–Fe³⁺ substitution, and the allanite group is light rare earth element enriched.

Distribution of major and trace elements during anatexis at the source area was investigated in a portion of Variscan mid–lower crust exposed at Palmi (Calabria, Italy). Reactive migration of migmatitic melt imparted a mineralogical and chemical signature in mafic rocks associated with migmatites and promoted the crystallization of amphibole by a coupled dissolution–precipitation process. Amphibole and accessory allanite control the distribution of incompatible elements from the anatectic zone.

Serpentines, magnesian clay-like minerals formed in subduction zones, contain iron in either ferrous or ferric form. The oxidation state of the iron form controls the composition of fluids that form when they are destabilized by heating. Results obtained here with Mössbauer spectroscopy are compared with X-ray spectroscopy and shown to be more reliable for serpentines and magnesium-rich chlorites. Fluids released by serpentines in subduction may be less oxidized than previously thought.

The near-infrared spectra of hydrous minerals involve OH stretching vibrations, but their interpretation is not straightforward due to anharmonicity and vibrational coupling. We analyze the spectra of well-ordered samples of talc, brucite and lizardite to better assess the various factors contributing to the absorption bands. The results clarify the relations between the overtone spectra and their fundamental counterparts and provide a sound interpretation of the two-phonon combination bands.

We present a detailed petrographic, microanalytical and bulk-chemical investigation of 36 mafic rocks from drill hole GT3A from the dike–gabbro transition zone. These varitextured gabbros are regarded as the frozen fillings of axial melt lenses. The oxide gabbros could be regarded as frozen melts, whereas the majority of the rocks, comprising olivine-bearing gabbros and gabbros, show a distinct cumulate character. Also, we present a formation scenario for the varitextured gabbros.

Combined Raman-scattering and wavelength-dispersive electron microprobe (WD-EMP) analyses of natural biotites expanding over the whole biotite solid-solution series demonstrate that the chemical composition of the MO₆ octahedra, TO₄ tetrahedra, and interlayer space can be non-destructively determined by Raman spectroscopy with relative uncertainties below 8 %. The content of critical minor elements such as Ti at the octahedral site can be quantified as well with a relative error of ~ 20 %.

In this work we report a new locality for the rare mineral hydroromarchite, Sn₃O₂(OH)₂. It was found not in a submarine environment but in soil at the Saint James Church archaeological site in Creussen, Germany. A tin artefact (a tin button) was exposed to weathering in soil for about 300 years. We solved and refined its structure based on single-crystal X-ray diffraction analysis.

We determined the physical conditions at the time of its entrapment for an inclusion pair hosted in a Siberian diamond (Udachnaya kimberlite) and found that it equilibrated under relatively oxidized conditions, near the enstatite–magnesite–olivine–diamond (EMOD) buffer, similarly to Udachnaya xenoliths originating from comparable depths. These results can be reconciled with models suggesting relatively oxidized, water-rich CHO fluids as the most likely parents for lithospheric diamonds.

It was determined that growth bands showing the straight birefringence in octahedral sectors and the enrichment of graphite inclusions in cuboid sectors of Zimbabwean mixed-habit diamonds may both be due to the fluctuation of temperature during crystallization, and they displayed positive anomalies of plastic deformation, residual stress, nitrogen concentration, and VN₃H defects. This conclusion clearly revealed the correlation between birefringence and spectroscopic properties of diamonds.

Minerals have complex crystal structures, but many common minerals are built from the same chemical building blocks. TotBlocks is a novel, open-source tool for investigating these structures. It consists of 3D-printed modules representing the silica tetrahedra and metal–oxygen octahedra that form the shared chemical building blocks of rock-forming minerals. TotBlocks is a low-cost visualization tool that relates mineral properties (habit, cleavage, and symmetry) to crystal structures.

We investigated the effect that fluoride and protons have on each other as structural neighbors in the mineral topaz. This was done using spectroscopic methods, which measure the interaction of electromagnetic radiation with matter. The forces between atoms distort the spectroscopic signals, and this distortion can thus be used to understand the corresponding forces and their effect on the physical properties of the mineral.