Quartz

Quartz is an abundant mineral in the Earth's continental crust. It 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. There are many different varieties of quartz, several of which are semi-precious gemstones. Throughout the world, varieties of quartz have been, since antiquity, the most commonly used minerals in the making of jewelry and hardstone carvings.