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.

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.

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.

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 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.

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.

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.