Recent  

This work presents new thermoelastic parameters and the structural evolution of burbankite at high pressure and high temperature, obtained by in situ synchrotron radiation single-crystal diffraction measurements. Burbankite is a carbonate that may potentially play a key role as an upper-mantle reservoir of light REE³⁺. We observed that the density of burbankite is greater with respect to carbonatitic magmas, indicating a possible fractionation of this phase in upper-mantle conditions.

Magmas transport large amounts of CO₂ from Earth's mantle into the atmosphere and thus contribute significantly to the global carbon cycle. We have developed an experimental method to homogenize at high pressure small liquid droplets trapped in magmatic crystals to gain access to the initial composition of the parental magma (major and volatile elements). With this technique, we show that magmas produced by melting of the subcontinental mantle contain several weight percent of CO₂.

The name sigismundite has been reinstated for what was previously arrojadite-(BaFe). Sigismundite honours Pietro Sigismund (1874–1962), and this paper outlines his significant contributions to Italian mineralogy.

A very representative type of historic brick, made of Mg- and Ca-rich illitic clays fired at high temperatures and used in the city of Padua, was studied. The mineral phases formed during the firing and the processes that took place after firing have enhanced the durability of the bricks, so the data obtained may be significant to the current ceramic industry. This study was framed within the CLAYONRISK project (MSCA-IF-2018) and was performed based on archeometric methodologies.

Rocks containing the serpentine mineral lizardite occur in many tectonic settings. Knowing the crystal orientation of lizardite in these rocks tells us how they deform and gives insights into their physical properties. The crystal orientation of lizardite is challenging to obtain using standard techniques. To overcome this challenge, we developed a method using Raman spectroscopy to map the crystal orientation of lizardite with minimal preparation on standard thin sections.

In this study we present a novel method for the automatic detection of minerals and elements using hyperspectral transmittance imaging microscopy measurements of complete thin sections (HyperTIM).

Common energy dispersive methods cannot accurately analyze low concentrations of cobalt in pyrite due to the overlapping of cobalt and iron peaks. The Raman method, on the other hand, has been shown to be very sensitive to a trace amount of cobalt. In addition, it can be applied on a rough surface, does not require a vacuum chamber, and operates with a laser instead of X-rays. Thus, Raman has the potential to be used as an assaying tool for Co-bearing pyrite.

Information about the local structure of tourmaline-group minerals can be obtained from the characteristic OH stretching bands in their vibrational spectra. However, their assignment to specific atomic-scale environments is debated. We address this question theoretically by investigating a series of dravite models. Our results support a local role of cationic occupancies in determining the OH stretching frequencies and bring constraints for the interpretation of the vibrational spectra.

The study of the original material of beraunite from the type locality Hrbek, Czech Rep., from collections of the TU Bergakademie Freiberg (Germany) and National Museum Prague (Czech Republic) proved the identity of the minerals beraunite and eleonorite. Because the name beraunite has priority, we consider the name eleonorite to be redundant and proposed to abolish it. The proposal 21-D approved by the IMA discredited eleonorite and accepted the formula of beraunite Fe³⁺₆(PO₄)₄O(OH)₄·6H₂O.

A reinvestigation of angastonite from the type locality has shown that it is a mixture of crystalline phases and an amorphous phase, with the published formula corresponding to the amorphous phase. A redefinition proposal for angastonite as an amorphous mineral was approved by the IMA CNMNC. Our study showed how the amorphous phase formed and how it progressively recrystallises as new crandallite-related minerals.

The equilibrium phase of A + HP clinoenstatite = forsterite + water was experimentally investigated at aH₂O = 1 in situ. In cold subducting slabs, it is of relevance to transport water to large depths, initiating the formation of dense hydrous magnesium silicate (DHMS). At normal gradients, the huge water amount from this reaction induces important processes within the overlying mantle wedge. We additionally discuss the relevance of this reaction for intermediate-depth earthquake formation.

The inclusions and exsolution lamellae in rainbow lattice sunstone (RLS) are studied using microscopic observations, chemical analyses and single-crystal X-ray diffraction. Complicated processes producing the aventurescence and adularescence effect in RLS are revealed through the spatial relationship among the inclusions and exsolution lamellae, as well as the unique ordering pattern in the feldspar structures.

We carried out theoretical calculations of the vibrational and thermophysical properties of Mg₂SiO₄ ringwoodite, a major mineral phase of the Earth's mantle transition zone. We tried to understand why current data on volume thermal expansion are still controversial by performing a detailed analysis of vibrational spectra. We proposed a reliable parametrization for thermal expansivity of ringwoodite in the transition zone which could be useful for numerical simulations of mantle convection.