sodium silicate, any one of several compounds containing sodium oxide, Na₂O, and silica, Si₂O, or a mixture of sodium silicates. Sodium orthosilicate is Na₄SiO₄ (or 2Na₂O·SiO₂); sodium metasilicate is Na₂SiO₃ (or Na₂O·SiO₂); sodium disilicate is Na₂Si₂O₅ (or Na₂O·2SiO₂); sodium tetrasilicate is Na₂Si₄O₉ (or Na₂O·4SiO₂). All these compounds are transparent, glassy or crystalline solids that have high melting points (above 800°C;) and are water soluble. They are produced chiefly by fusing sand and sodium carbonate in various proportions. The product is commonly known as water glass. The greatest single use of sodium silicates is as a raw material for making silica gel.

silicate, chemical compound containing silicon, oxygen, and one or more metals, e.g., aluminum, barium, beryllium, calcium, iron, magnesium, manganese, potassium, sodium, or zirconium. Silicates may be considered chemically as salts of the various silicic acids. For a long time classified as ortho-, meta-, di-, or trisilicates according to the acid from which they are (theoretically) derived, they are now also classified by an X-ray diffraction method according to their crystalline structure. Silicates are widely distributed in nature, making up most of the earth's outer crust. Most of the common rock-forming minerals (e.g., quartz, feldspar, mica, and pyroxene) are silicates, as are asbestos, beryl, aquamarine, emerald, serpentine, and talc. Clay consists essentially of hydrous aluminum silicates mixed with other substances. Glass is a mixture of silicates, as is water glass. See sodium silicate.

Any of a large group of silicon-oxygen compounds that are widely distributed throughout much of the solar system. The silicates make up about 95percnt of the Earth's crust and upper mantle, occurring as the major constituents of most igneous rocks and in appreciable quantities in sedimentary and metamorphic rocks. They also are important constituents of lunar samples, meteorites, and most asteroids. In addition, planetary probes have detected them on the surfaces of Mercury, Venus, and Mars. Of the approximately 600 known silicate minerals, only the feldspars, amphiboles, pyroxenes, micas, olivines, feldspathoids, and zeolites are significant in rock formation.

Learn more about silicate mineral with a free trial on Britannica.com.