This phase diagram shows the different crystal structures that silica (SiO2) can take on depending on temperature and pressure conditions. At normal atmospheric pressure and temperatures, silica exists as alpha quartz. However, as pressure or temperature increases, it transitions to other structures like tridymite, cristobalite, coesite, and eventually stishovite at very high pressures over 10 GPa.

7. Stishovite
Coesite
α- quartz
β- quartz
Liquid
Tridymite
Cristobalite
600 1000 1400 1800 2200 2600
2
4
6
8
10
Pressure(GPa)
Temperature oC

8. P6P6222222
P3P3222121