Quartz (SiO2), also known as deep quartz or α-quartz, belongs to the group of minerals and has a crystalline, external structure (trigonal symmetry). Quartz is the stable variant of silicon dioxide, a mineral found on the earth's surface. After feldspar in its various forms, quartz is the second most common mineral in the earth's crust. It has a Mohs hardness of 7 and is therefore a hard mineral. Quartz occurs in different forms and colors and is mainly used in the cement, ceramics and glass industries.
