ETYM German quarz.
Crystalline form of silica SiO2, one of the most abundant minerals of the Earth’s crust (12% by volume). Quartz occurs in many different kinds of rock, including sandstone and granite. It ranks 7 on the Mohs’ scale of hardness and is resistant to chemical or mechanical breakdown. Quartzes vary according to the size and purity of their crystals. Crystals of pure quartz are coarse, colorless, and transparent, and this form is usually called rock crystal. Impure colored varieties, often used as gemstones, include agate, citrine quartz, and amethyst. Quartz is used in ornamental work and industry, where its reaction to electricity makes it valuable in electronic instruments (see piezoelectric effect). Quartz can also be made synthetically.
Crystals that would take millions of years to form naturally can now be “grown” in pressure vessels to a standard that allows them to be used in optical and scientific instruments and in electronics, such as quartz wristwatches.
A hard glossy mineral consisting of silicon dioxide in crystal form; present in most rocks (especially sandstone and granite); yellow sand is quartz with iron oxide impurities.

The 2-D drawing engine that forms the imaging foundation of the Mac OS X Aqua interface. The Quartz graphics application programming interface (API) is based on Adobe’s Portable Document Format (PDF) standard.