Direct transition from cristobalite to post-stishovite α-PbO2-like silica phase

In situ, x-ray studies in diamond anvil cells at pressures over 80 GPa were used to determine a stable silica phase at extreme conditions. We demonstrate that so far unidentified phases obtained on compression of α-cristobalite and a new dense silica polymorph discovered in the Martian meteorite Shergotty is the α-PbO₂-type silica.