Which compound is the primary component of quartz?

Silicon dioxide is the primary component of quartz.

Silicon dioxide, also called silica, has the chemical formula SiO₂. In quartz, each silicon atom is bonded within a large three-dimensional network of silicon and oxygen atoms. This structure gives quartz considerable hardness and chemical stability.

Quartz is one crystalline form of silica, but silica can also occur in other forms, including amorphous glass and minerals such as tridymite and cristobalite. Quartz is widespread in Earth’s crust and is a major component of many rocks, especially granite, sandstone, and some sedimentary deposits.

Silicon dioxide is not the same as silicon carbide, which contains carbon and is much harder. Calcium carbonate is the main compound in many limestones and shells, while aluminum oxide occurs in minerals such as corundum. Those compounds can appear in rocks alongside quartz, but they do not define quartz’s composition.