Quartz is one of the most abundant minerals and is composed of silicon dioxide (SiO2). It has a complex crystal structure and exists in several polymorphs including alpha-quartz, beta-quartz, tridymite, cristobalite, coesite, and stishovite. The stability of these polymorphs depends on temperature and pressure conditions. Cryptocrystalline varieties of quartz include chalcedony, agate, jasper, chert, and flint. Macrocrystalline varieties include rock crystal, milky quartz, amethyst, rose quartz, citrine, and smoky quartz.

1. SILICA MINERALS Quarz, Trydymite and Crystobalite.

5. Mineral Groups – Silicates Quartz light silicates (pure SiO 2 ) no cleavage (conchoidal fracture) hard, resistant to weathering Quartz

8. 1 - C Systems 1. The system SiO 2 Fig. 6-6. After Swamy and Saxena (1994), J. Geophys. Res., 99, 11,787-11,794 . AGU