It is shown here that the H₂O content of hydrous minerals can be determined from their mean refractive indices with high accuracy. This is especially important when only small single crystals are available. Such small crystals are generally not suitable for thermal analyses or for other reliable methods of measuring the amount of H₂O. The results are compared with the observed H₂O content evaluating 157 zeolite-type compounds and 770 non-zeolitic hydrous compounds, showing good agreement.

The paper presents experimental results on the growth of diamonds in Fe–Ni melt together with silicate minerals at high P–T. The morphology of the grown diamonds was studied, as well as the chemical composition of the synthetic silicates. This work builds on our preliminary experimental work presented in Zhimulev et al. (2012), which was an experimental evidence to confirm the hypothesis of crystallization of diamonds from metallic liquids explained in a pioneer paper by Smith et al. (2016).

Our research found that the cookeite crystallized within a closed space (e.g., crystal-rich inclusion, CI, in pegmatites) at relatively high P–T conditions might bear distinct and high-purity Raman signals. As a result, this type of cookeite is unusual and provides an indicator of cookeite crystallized in the closed spaces of a primary inclusion (e.g., CI), beneficial for recognizing the primary nature of the CIs in pegmatites and understanding the formation mechanisms of CIs and pegmatites.

This paper describes the characterization of a new mineral from the Oumlil mine in the Bou Azzer cobalt mining district in Morocco. This mining district is one of the world's largest producers of the important element cobalt. This study on the new mineral halilsarpite provides useful information on the results of chemical weathering processes on the primary arsenide minerals at the mine.

The Neolithic polished stone industry of Chiomonte was studied with a multi-analytical approach, with the aim of providing information about the raw material origins and supply sources. Most tools are made of greenstones. Specific mineral and chemical markers were found, pointing to an origin in the Monviso area. The presence on roughouts and broken tools with raw surfaces ascribable to pebbles or cobbles suggests that these rocks had been picked up from glacial or alluvial secondary sources.

Feldspars are the most abundant minerals in the Earth's crust. Their structural behaviour is complicated because order/disorder reactions, phase transitions, and unmixing processes interact. Liu et al. (2018) claim that the water content in the nominally dry feldspars has a profound influence on the transformation behaviour. Their arguments, however, are not sound. We point to a number of errors and omissions.

We experimentally explored direct entrapment of breyite (CaSiO₃) by diamond at upper-mantle conditions in a model subducted sediment rather than formation by retrogression of CaSiO₃ perovskite, implying a deeper origin. Anhydrous low-T melting of CaCO₃+SiO₂ precludes breyite formation. Under hydrous conditions, reduction of melt results in graphite with breyite. Thus, breyite inclusions in natural diamond may form from aragonite + coesite or carbonate melt at 6–8 GPa via reduction with water.

There have been many different ages found for ophiolite. We have researched these ages through fieldwork and microscopy to identify three types of dunite. These are useful ways to research the origin of ophiolitic magma. The Purang ophiolite, which crops out over an area of about 650 km² in the western Yarlung–Zangbo suture zone, chiefly consists of mantle peridotite, pyroxenite and gabbro. It is a useful ultra-massif for showing the multistage nature of ophiolite.