Despite the fact that rock textures depend on the 3D spatial distribution of minerals, our tectono-metamorphic reconstructions are mostly based on a 2D visualisation (i.e. thin sections). For 2D a thin section scan has been combined with chemical X-ray maps, whereas for 3D the X-ray computerised axial microtomography (μCT) has been applied. This study corroborates the reliability of the thin section approach, still emphasising that 3D visualisation can help understand rock textures.

In this paper, the full description of the extremely rare [Ag₆]⁴⁺-cluster-containing new tetrahedrite-group mineral kenoargentotetrahedrite-(Zn) is reported. The structure refinement result confirms the coupling between the site occupancy factor of subvalent hexasilver clusters at the M(2) site and that of the vacancy at the S(2) site. This relationship further substantiates the charge balance substitution mechanism of S-deficiency tetrahedrites: 6^M(2)Ag⁺ + ^S(2)S^2– = ^M(2)[Ag₆]⁴⁺ + ^S(2)□.

Inclusions in natural rocks are an invaluable asset for geoscientists because they provide information about processes in the Earth's history that are otherwise hidden or subsequently overprinted. In this paper we review the development over the last 200 years of the concepts and methods to measure the remnant pressures in mineral inclusions and how they can be used to determine pressures and temperatures at which the inclusions were formed deep within the Earth.

This paper presents the results of an exploratory study on the pressure–volume–temperature behaviour of the main Mg-phosphates of geological interest, especially in high-pressure metamorphic rocks. The incentive for it was the growing body of experimental phase-equilibrium data acquired at high pressure in the MgO–(Al₂O₃)–P₂O₅–H₂O systems, the thermodynamic evaluation of which has been begging for such volumetric data.

In situ Lu–Hf geochronology of garnet is applied to date a Finnish lithium–caesium–tantalum (LCT) pegmatite from the Somero–Tammela pegmatite region. The age obtained was 1801 ± 53 Ma, which is consistent with zircon ages of 1815–1740 Ma obtained from the same pegmatite. We show the in situ Lu–Hf method is a fast way of obtaining reliable age dates from LCT pegmatites.

The structure of beryl has been a topic of research for decades but is still not entirely understood. This especially applies to substitutions by Fe ions and the occupation of the channels of beryl by H₂O and alkalis. The growing amount of studies makes it difficult to gain an overview on these topics. Therefore, this article reviews the current consensus and debates found in the literature.

The piston–cylinder apparatus is widely used to investigate rock properties at the conditions of the interior of the Earth, but uncertainty in its calibration of pressure persists, with substantial differences between laboratories. We use a ceramic of magnesium and zinc oxides to measure the conditions experienced by a sample. Routine use of such ceramics provides an archive of experimental conditions, enables interlaboratory comparisons, and resolves long-standing controversies in calibration.

This work presents the results on deformation-enhanced melt segregation and extraction in a phonolitic magma emplaced at shallow depth in the Velay volcanic province (France). We provide evidence of the segregation and subsequent extraction of the residual melt during magma ascent and final emplacement. We highlight that melt segregation started by compaction as a loose packing of microlites emerged and continued with melt filling of a shear band network.

Zvěstovite-(Fe) is a new, Ag-rich, member of the tetrahedrite group, the most widespread sulfosalts in ore deposits. Its discovery stresses the chemical variability of this mineral group, allowing for a better understanding of the structural plasticity of these compounds, which are able to host a plethora of different elements typical of hydrothermal environments. 

The paper describes the characterisation of fluor-rewitzerite, a new mineral species belonging to the paulkerrite group. The crystal structure of fluor-rewitzerite has been refined using microfocus synchrotron diffraction data, which allowed 25 of the possible 30 H atoms to be located, thus establishing key features of the H bonding. Crystallochemical trends are reviewed for seven recently characterised monoclinic paulkerrite-group minerals.