Akaogiite
Akaogiite is a high-pressure polymorph of titanium dioxide (TiO2), specifically the rutile structure. It is named after Masaki Akaogi, a professor at Gakushuin University in Tokyo, Japan, who has made significant contributions to high-pressure mineral physics. Akaogiite is formed under extreme pressure conditions, typically found within the Earth's lower mantle.
Unlike rutile, anatase, and brookite (the common low-pressure polymorphs of TiO2), akaogiite's crystal structure is denser due to the immense pressure under which it forms. This increased density affects its physical properties, such as its refractive index and hardness. It is believed to play a role in the geochemical cycling of titanium within the Earth's interior and can influence seismic wave velocities.
Akaogiite is not typically found on the Earth's surface due to its instability at ambient pressure. However, it can be preserved in shock-metamorphosed meteorites that have experienced high-pressure events upon impact. The presence of akaogiite in such meteorites provides valuable information about the conditions and processes that occurred during those impact events.
The study of akaogiite involves high-pressure experiments in laboratories using diamond anvil cells or multi-anvil presses to simulate the conditions of the Earth's mantle. These experiments help scientists understand the behavior of TiO2 at extreme pressures and its implications for the Earth's internal structure and dynamics. The determination of its stability field and physical properties contributes to our understanding of the composition and evolution of the deep Earth.