A hard, crystalline form of silicon dioxide. Quartz is one of the most common minerals in the earth's crust and occurs as grains (sand), masses (agate, bloodstone, chalcedony, jasper, carnelian, etc.) or crystals (rock crystal, amethyst, citrine, smoky quartz, rose quartz, etc.). Quartz usually crystallizes in hexagonal prisms or pyramids. It has been mined or gathered as a semiprecious stone since Paleolithic times. Quartz is a piezoelectric crystal, i.e. generates an electrical force when placed under pressure. Additionally, quartz crystals are used in polarized light microscopy because they can rotate the plane of polarized light. Some crystalline forms of quartz are used as gemstones, such as amethyst and citrine. Sand is the primary component in the manufacture of glass, and is an additive in porcelain, brick, cement, and mortar. Because of its hardness, quartz is also used as an abrasive in stonecutting, sandblasting, and glass grinding.
Synonyms and Related Terms
sand; agate; bloodstone; chalcedony; jasper; carnelian; sard; rock crystal (colorless); amethyst (purple); citrine (yellow); onyx; rose quartz (pink); smoky quartz (brown to black); yellow quartz; milky quartz (milk white); chrysoprase; kvarts (Dan., Nor., Sven.); Quarz (Deut.); cuarzo (Esp.); quartz (Fr.); quarzo (It.); kwarts (Ned.); kwarc (Pol.); quartzo (Port.)
Insoluble in acids except for hydrofluoric acid. Slightly soluble in alkalis.
Trigonal crystal system. Low birefringence. Low thermal expansion.
Fracture = conchoidal. Luster = vitreous to greasy. Streak = white.
Microscopically, particles are transparent. Crossed polars shows low virefringence and first order grays
|Molecular Weight||mol. wt. = 60.08|
|Refractive Index||1.544; 1.553|
Hazards and Safety
Noncombustible. Inhalation of fine particles may cause silicosis.
Mallinckrodt Baker: MSDS
Mineralogy Database: Quartz
Sources Checked for Data in Record
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