Quartz (SiO₂), also known as silicon dioxide, is a common mineral that is the product of the two most prevalent elements in the Earth's crust--silicon and oxygen. It can be found as giant crystals or small grains, and is the main component of most types of sand. It is the hardest common mineral and for this reason is often used in the making of sandpaper, grindstones, polishers, and industrial cleaners. Though it is clear and glassy in its large crystal form, called rock quartz, it also can be found in several shades of coloration, the most familiar being rose quartz (pink), smoky quartz (brown), and amethyst (purple).

Quartz has a variety of scientific and industrial uses, chiefly because it possesses piezoelectricity. Discovered by the French physicist Pierre Curie, the piezoelectric effect is a phenomenon demonstrated by certain crystals: when squeezed or stretched, a voltage is produced across the...