Akaogiite

Akaogiite (IMA symbol Aka) is an exceedingly rare mineral, one of the natural forms of titanium dioxide (TiO₂). It is a high-pressure polymorph of TiO₂, along with anatase, brookite and another high-pressure phase called "TiO₂ II". Rutile is the stable polymorph of TiO₂, most commonly found at standard temperatures and pressures.

Akaogiite can be found at the Nördlinger Ries Crater, a meteor crater in Germany, where the extreme pressure during the impact allowed its formation.