Quartz is the second most abundant mineral on the Earth's surface. It consists of one part silicon and two parts oxygen, with a chemical composition of SiO2. It occurs in hexagonal crystal forms and exhibits a variety of colors and shapes, but it is commonly colorless or white. Quartz is known for its glassy luster and has a hardness of 7 on the Mohs scale, meaning it can scratch glass and all types of iron. It also displays conchoidal fracture.