The first occurrence of centimeter-thick PS-15 polygonal serpentine veins from ultramafics of Monte Avic, Val d'Aosta, is here reported. The combined mineralogical study led by three techniques with different resolutions has provided new analytical tools capable of recognizing the PS-15 polygonal serpentine. In particular, X-ray powder diffraction data (XRPD) and micro-Raman recognize polygonal serpentine more quickly and easily than transmission electron microscopy (TEM) but equally rigorously.

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.

The mineralogical and chemical heterogeneity of the mantle is poorly known because it is not able to be directly investigated. Melt–peridotite interaction processes play a fundamental role in controlling the mantle composition. The results of our reaction experiments help us to evaluate the role of temperature and melt composition in the modification of the mantle through the interaction with pyroxenite-derived melts with implications for the evolution of a veined mantle.

Amphibole–liquid partitioning of elements of geological relevance is experimentally derived at conditions compatible with those of the Earth's upper mantle. Experiments are carried out at different oxygen fugacity conditions and variable Cl content in order to investigate their influence on the amphibole–liquid partition coefficients. Our results point to the capability of amphibole to act as filter for trace elements at upper-mantle conditions, oxidized conditions, and Cl-rich environments.

Detailed knowledge of the mechanisms ruling water incorporation in amphibole is essential to understand how much water can be fixed at upper-mantle conditions by this mineral. We provide the experimental evidence of the Cl effect on the oxo-substitution and the incorporation of water in amphibole. Finally, we highlight the versatility of confocal micro-Raman spectroscopy as an analytical tool to quantify water in amphibole.

Unusually large lizardite (Lz) crystals from Monte Fico serpentinites, Elba (Mellini and Viti, 1994), have allowed several subsequent studies. During a µ-Raman study of serpentine minerals (Compagnoni et al., 2021), the careful microscopic examination of this Lz showed spongy microstructure. TEM observations confirmed that the Lz hosts voids, filled with chrysotile and polygonal serpentine; their mutual relationships indicate that Lz grew up with a skeletal habit and fibres epitactically.