Quartz is a very common mineral in the Earth’s crust. Chemically, quartz is silica, or silicon dioxide, SiO₂. It is found in most types of rocks: igneous, metamorphic and sedimentary.

Quartz is physically and chemically resistant to weathering. When quartz-bearing rocks become weathered and eroded, the grains of resistant quartz are concentrated in the soil, in rivers, and on beaches. The white sands typically found in river beds and on beaches are usually composed mainly of quartz, with some white or pink feldspar as well.

Because of its abundance and distinctive crystal shape, quartz has been recognized as a mineral for thousands of years. The name has an uncertain origin, possibly derived from the German word quarz, a word of ancient and uncertain origins.

When water-clear, quartz is known as rock crystal or mountain crystal. However, quartz can contain a number of different impurities, which create different color varieties. Purple quartz is known as amethyst; white is milky quartz; black is smoky quartz; pink is rose quartz, and yellow or orange is citrine.