Quartz

Quartz is a hard, crystalline mineral composed of silica. It classified structurally as a framework silicate mineral and compositionally as an oxide mineral. Quartz is the second most abundant mineral in Earth’s continental crust, behind feldspar.

There are many different varieties, several of which are classified as gemstones. Since antiquity, varieties of quartz the most commonly used minerals in the making of jewelry and hardstone carvings. Especially in Europe and Asia.

It is the mineral defining the value of 7 on the Mohs scale of hardness, a qualitative scratch method for determining the hardness of a material to abrasion.