How does quartz transform into stishovite under high pressure?

Quartz transforms into stishovite through a structural rearrangement driven by high pressure, typically occurring at approximately 8 GPa.1

Under normal conditions, quartz consists of a three-dimensional array of silicon atoms coordinated by four oxygen atoms in a tetrahedral arrangement. When subjected to sufficiently high pressure, this structure becomes unstable, forcing the silicon atoms to coordinate with six oxygen atoms instead. This transition results in a denser, more closely packed atomic arrangement characterized by a rutile-type tetragonal structure.213

Because this process requires extreme pressure, stishovite is rarely found in Earth's crust. It is most commonly observed in meteorite craters, where the kinetic energy from large-scale impacts imparts the necessary pressure to convert quartz-rich sandstones into this dense polymorph.435