Partition coefficients are key to petrological modelling yet hard to estimate independently of measurements. Here we model the partitioning of Cr between garnet and clinopyroxene ab initio. Incorporation of Cr into crystal structures causes strain, and its energetic toll defines whether Cr favours one mineral or another. Comparing to Cr content in metamorphic rocks shows how mineral composition and structure set equilibrium partition coefficients and how kinetics hampers equilibrium.

Laurentthomasite is a new mineral from Madagascar showing a very strong dichroism going from deep blue to yellow-green colours. The physical and chemical characteristics of this gem quality mineral bring it to the attention of the jewel industry as well as collectors of cut stones.

Molybdates are of a great interest due to their ionic conductivity, negative thermal expansion, and immobilization of radionuclides. The new mineral tancaite-(Ce), FeCe(MoO₄)₃•3H₂O, shows a new structure type never observed in natural and synthetic molybdates. Its cubic average structure may be described as a derivative of the perovskite structure, in which Fe-centred octahedra are linked through MoO₄ groups. The ordering of Mo and O atoms results in one or more complex superstructures.

Rhönite in the Cenozoic alkali basalts of the Changle area occurs as a reaction product; the host basalts are generated in an extensional setting of intracontinent and are tectonically located above the old subduction zone. Rare-earth-element patterns of rhönite resemble those of kaersutitic amphibole and kaersutite. Compositions of Changle rhönites covering the two types of metasomatic mantle amphiboles further suggest that rhönite could be seen as the role of petrogenetic indicator mineral.

Quartz is a very common form of almost pure silica. It can contain a small concentration of hydrogen-bearing defects whose nature is still debated. Here, we use a theoretical approach to unravel the atomic-scale geometry of these defects. Our findings help explain some important quartz properties.