Direct transition from cristobalite to post-stishovite α-PbO 2 -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. This paper was presented at the EMPG VIII meeting in Bergamo, Italy (April 2000)

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