https://phys.org/news/2018-10-scientists-results-inorganic-pigments-apatite.html

The search for a crystalline matrix that promotes stabilization of the rare oxidation states of manganese and chromium is relevant due to the fact that such compounds have a persistent green or blue color (or their intermediate shades). Therefore, it is possible to use them as inorganic pigments, which, in addition to their specific shades, feature a sufficiently high thermal stability.

The studies of inorganic pigments with the apatite structure have been carried out at the Faculty of Chemistry of the Lobachevsky University by the team headed by Prof. A.V. Knyazev and Dr. E.N. Bulanov since 2010. The team's latest achievements include obtaining a high-purity sample of the composition Ba5(MnO4)3Cl and its physico-chemical characterization. According to Evgeny Bulanov, within the framework of this research, the features of the crystal structure and chemical environment were established, allowing the degree of manganese oxidation to be stabilized.