Quartz has been extensively examined under both static and dynamic compression due to its wide application in both geophysics and materials science. SiO2 is one of the most abundant minerals on the Earth’s crusts and is widely distributed in different rock types. As a result, the behavior of quartz under dynamic loading is essential for modeling the effects of meteorite impacts and explosions. The shock compression behavior of quartz is characterized by a phase transition occurring over a broad ‘mixed-phase region’ (~15-40 GPa). Despite decades of study, the nature of this transformation and the identity of the high-pressure phase(s) remain poorly understood.
In this study, we collected in situ x-ray diffraction on shock-compressed polycrystalline quartz using natural low-porosity novaculite samples. The crystal structure of the compressed material was investigated under shock loading through a series real time x-ray diffraction measurements with peak stress ranging from 26 to 66 GPa. These results demonstrate that novaculite adopts a disordered stishovite-like structure on the Hugoniot, likely as result of kinetic limitations in transforming from four-fold alpha quartz to six-coordinated stishovite on the 100-ns timescale of gas-gun experiments.