Defining mineralogy of extreme conditions as a subfield in geoscience is meaningful only with respect to specific scientific tasks that it shall address. In case of mineralogy of extreme conditions there are two principal tasks: the deep Earth and large scale impacts on Earth or between meteorite-parent bodies. There
are plausible extensions such as to pseudotachylites from earthquakes, but I focus in my talk on these two principal topics.
After briefly introducing the method, I will review the progresses in the understanding of impacts based on the recent achievements in shock-metamorphic mineralogy. Emphasis is put on the discovery of bridgmanite as a case study how solving a particular, challenging problem can open new areas of research.
Shock-induced high pressure mineralogy probes an extensive compositional space, often beyond of what is experimentally achievable. I will show how this extensive set of compositions and structures allows us to define thermodynamic mixing relations and endmembers of important rock-forming or accessory minerals with application to deep Earth. This is the second topic of my talk: I will show the mixing relations of ferrous-ferric bridgmanite and how it explains some of the properties of this mineral. Then I show that the current concept of solid solutions of majorite-bearing garnets is incorrect and outline the crystal chemistry of majoritic garnets.