Microstructural Observations of α-Quartz Amorphization

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Abstract
Solid-state amorphization is a transformation that has been observed in a growing number of materials. Microscopic observations indicate that amorphization of a-quartz begins with formation of crystallographically controlled planar defects and is followed by growth of amorphous silicon dioxide at these defect sites. Similar transformation microstructures are found in quartz upon quasihydrostatic and nonhydrostatic compression in a diamond-anvil cell to 40 gigapascals and from simple comminution. The results suggest that there is a common mechanism for solid-state amorphization of silicates in static and shock high-pressure experiments, meteorite impact, and deformation by tectonic processes. In general, these results are consistent with recently proposed shear instability models of amorphization.