High-Pressure Mineral Phases

Mineral forms that are stable only at the extremely high pressures typical of Earth’s deep interior, but not its surface. Such pressures also are generated instantaneously during meteorite impact. For example, coesite and stishovite are high-pressure polymorphs of SiO2 (silica) and diamond is a high-pressure modification of graphite (carbon).

Image Source: www.le.ac.uk, J. Tarney

The minerals in mantle rocks undergo phase changes with depth, transforming into denser forms. Particularly notable are the transformations that occur near 400 and 700 km depth. The former corresponds to pyroxene transforming into a garnet structure.

Image Source: www.le.ac.uk, J. Tarney

Some or all content above used with permission from J. H. Wittke.

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