high pressure dressing for quartz

At relatively low pressures, three crystalline minerals of silica are stable: quartz, tridymite and cristobalite. High-pressure solid phases, such as coesite and stishovite, can be safely disregarded for our purposes. Quartz and cristobalite have a low- and a high-temperature modification, called α- and β-, respectively (Deer et al., 1992).