Quartz is a crystalline form of

Quartz is made up of a continuous framework of SiO₄ silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO₂. Tridymite and cristobalite are hightemperature polymorphs of SiO₂ that occur in highsilica volcanic rocks. Coesite is a denser polymorph of quartz found in some meteorite impact sites and in metamorphic rocks.