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In chemistry, a silicate is a compound consisting of silicon and oxygen (SixOy), one or more metals, and possibly hydrogen. It is also used to denote the salts of silica or of one of the silicic acid s. Silicate minerals are noted for their tetrahedral form. Sometimes the tetrahedra are joined in chains, double chains, sheets, and three-dimensional frameworks. They are subclassified into groups based on the degree of polymerization of the tetrahedra, such as nesosilicates, cyclosilicates, and so forth.
In geology and astronomy, the term silicate is used to denote a type of rock that consists of silicon and oxygen (usually as SiO2 or SiO4), one or more metals, and possibly hydrogen. Such rocks range from granite to gabbro. Most of the Earth's crust is made up of silicate rocks, as are the crusts of other terrestrial planets.
Mineralogically, silicate minerals are divided according to their molecular structure into the following groups:
- OlivineThe mineral olivine is a magnesium iron silicate with the formula (Mg,Fe)SiO in which the ratio of magnesium and iron varies between the two endmembers of the series: forsterite (Mg-rich) and fayalite (Fe-rich). It gives its name to the group of minerals (single tetrahedron) - Nesosilicates
- EpidoteEpidote a mineral species consisting of basic calcium aluminium and iron orthosilicate, Ca(Al, Fe)(SiO)(OH), crystallizing in the monoclinic system. Well-developed crystals are of frequent occurrence: they are commonly prismatic in habit, the direction of (double tetrahedra) - Sorosilicates
- TourmalineThe mineral tourmaline is chemically one of the most complicated silicate minerals. It is a complex silicate of aluminium and boron but because of isomorphous replacement (solid solution) its composition varies widely with iron, magnesium and lithium and (rings of tetrahedra) - Cyclosilicates
- PyroxenePyroxenes are a group of rock-forming silicate minerals. They are comprised of single chains of silica tetrahedra and have the general formula XY(Si,Al)O. X represents calcium, sodium, iron+2 and magnesium and more rarely zinc, manganese and lithium. (single chain) - Inosilicates
- AmphiboleHornblende) Amphibole defines an important group of dark-colored rock-forming silicate minerals composed of double chain SiO tetrahedra linked at the vertices and generally containing ions of iron and/ or magnesium in their structures. In chemical composi (double chain) - Inosilicates
- MicaThe mica group of minerals includes several closely related materials having highly perfect basal cleavage. All are monoclinic with a tendency towards pseudo-hexagonal crystals and are similar in chemical composition. The highly perfect cleavage, which iss and clayFor the town in the United States, see Clay, New York. Clay is a generic term for an aggregate of hydrous silicate particles less than 4 micrometers in diameter. It consists of small crystals of the minerals silica (SiO) and alumina (AlO). These elements,s (sheet) - Phyllosilicates
- FeldsparFeldspar (from the German Feld field, and Spat a rock that does not contain ore) is the name of an important group of rock-forming minerals which make up perhaps as much as 60% of the Earth's crust. They crystallize from magma in both intrusive and extruss (framework) - Tectosilicates
- Quartz (SiO2 framework)
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