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Encyclopedia > Silicate

In chemistry, a silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. This definition is broad enough to include species such as hexafluorosilicate ("fluosilicate"), [SiF6]2−, but the silicate species that are enocuntered most often consist of silicon with oxygen as the ligand. Silicate anions, with a negative net electrical charge, must have that charge balanced by other cations to make an electrically neutral compound. Chemistry (from Greek χημεία khemeia[1] meaning alchemy) is the science of matter at the atomic to molecular scale, dealing primarily with collections of atoms, such as molecules, crystals, and metals. ... An anion is an ion with negative charge. ... General Name, Symbol, Number silicon, Si, 14 Chemical series metalloids Group, Period, Block 14, 3, p Appearance dark gray, bluish tinge Atomic mass 28. ... In chemistry, a ligand is an atom, ion, or molecule (see also: functional group) that generally donates one or more of its electrons through a coordinate covalent bond to, or shares its electrons through a covalent bond with, one or more central atoms or ions (these ligands act as a... General Name, Symbol, Number silicon, Si, 14 Chemical series metalloids Group, Period, Block 14, 3, p Appearance dark gray, bluish tinge Atomic mass 28. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ...


Silica, or silicon dioxide, SiO2, is sometimes considered a silicate, although it is the special case with no negative charge and no need for counter-ions. Silica is found in nature as the mineral quartz, and its polymorphs. R-phrases R42 R43 R49 S-phrases S22 S36 S37 S45 S53 Flash point non-flammable Supplementary data page Structure and properties n, εr, etc. ... Minerals are natural compounds formed through geological processes. ... Quartz is one of the most common minerals in the Earths continental crust. ... Polymorphism in materials science is the ability of a solid material to exist in more than one form or crystal structure. ...


In the vast majority of silicates, including silicate minerals, the Si atom shows tetrahedral coordination by 4 oxygens. In different minerals the tetrahedra show different degrees of polymerization: they occur singly, joined together in pairs, in larger finite clusters including rings, in chains, double chains, sheets, and three-dimensional frameworks. The minerals are classified into groups based on these anion structures; a list is given below. The silicate minerals make up the largest and most important class of rock-forming minerals. ... A tetrahedron (plural: tetrahedra) is a polyhedron composed of four triangular faces, three of which meet at each vertex. ... Minerals are natural compounds formed through geological processes. ... Polymer is a term used to describe large molecules consisting of repeating structural units, or monomers, connected by covalent chemical bonds. ...


Silicon may adopt octahedral coordination by 6 oxygens at very high pressure, as in the dense stishovite polymorph of silica that is found in the lower mantle of the Earth, and which is also formed by shock during meteorite impacts. Lack of space around the oxygen atoms makes this coordination for Si very rare at normal pressure, but it is known in the hexahydroxysilicate anion, [Si(OH)6]2−, as found in the mineral thaumasite. An octahedron (plural: octahedra) is a polyhedron with eight faces. ... Stishovite is a form of silicon dioxide that is formed at very high pressure (~ 100 kbar) and temperature (> 1200 ° C), so far as is known only in meteorite impact craters and their ejecta. ... The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... Willamette Meteorite A meteorite is an extraterrestrial body that survives its impact with the Earths surface without being destroyed. ...


Silicate rock

In geology and astronomy, the term silicate is used to denote types of rock that consists predominantly of silicate minerals. Such rocks include a wide range of igneous, metamorphic and sedimentary types. Most of the Earth's mantle and crust are made up of silicate rocks. The same is true of other terrestrial planets. World geologic provinces Oceanic crust  0-20 Ma  20-65 Ma  >65 Ma Geologic provinces  Shield  Platform  Orogen  Basin  Large igneous province  Extended crust Geology (from Greek γη- (ge-, the earth) and λογος (logos, word, reason))[1] is the science and study of the solid matter of a celestial body, its composition... A giant Hubble mosaic of the Crab Nebula, a supernova remnant. ... The rocky side of a mountain creek near Orosí, Costa Rica. ... Igneous rocks are formed when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ... Quartzite, a form of metamorphic rock, from the Museum of Geology at University of Tartu collection. ... Two types of sedimentary rock: limey shale overlaid by limestone. ... Earth cutaway from core to exosphere. ... Earth cutaway from core to exosphere. ... The eight planets and three dwarf planets of the Solar System. ...


On Earth, a wide variety of silicate minerals occur in an even wider range of combinations as a result of the processes that form and re-work the crust. These processes include partial melting, crystallization, fractionation, metamorphism, weathering and diagensis. Living things also contribute to the silicate budget near the Earth's surface. A type of plankton known as diatoms construct their exoskeletons, known as tests, from silica. The tests of dead diatoms are a major constituent of deep ocean sediment In physics, melting is the process of heating a solid substance to a point (called the melting point) where it turns liquid. ... Crystal (disambiguation) Insulin crystals A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ... Fractional distillation is the separation of a mixture of compounds by their boiling point, by heating to high enough temperatures. ... Metamorphism can be defined as the mineralogical, chemical and crystallographic changes in a solid-state rock, i. ... Weathering is the process of disintegration of rocks, soils and their minerals through direct, or indirect contact with the atmosphere. ... This article or section does not cite its references or sources. ... Diatoms (Greek: (dia) = through + (temnein) = to cut, i. ... An exoskeleton, in contrast to an endoskeleton, is an external anatomical feature that supports and protects an animals body. ... The deep ocean is the lowest layer in an ocean, existing below the thermocline. ... Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of water or other liquid. ...


Mineralogy

Mineralogically, silicate minerals are divided according to structure of their silicate anion into the following groups: Mineralogy is an earth science that involves the chemistry, crystal structure, and physical (including optical) properties of minerals. ... The silicate minerals make up the largest and most important class of rock-forming minerals. ...

  • Nesosilicates (lone tetrahedron) - [SiO4]4−, eg olivine.
  • Sorosilicates (double tetrahedra) - [Si2O7]6−, eg epidote.
  • Cyclosilicates (rings) - [SinO3n]2n−, eg tourmaline group.
  • Inosilicates (single chain) - [SinO3n]2n−, eg pyroxene group.
  • Inosilicates(double chain) - [Si4nO11n]6n−, eg amphibole group.
  • Phyllosilicates (sheets) - [Si2nO5n]2n−, eg micas and clays.
  • Tectosilicates (3D framework) - [AlxSiyO2(x+y)]x−, eg quartz, feldspars, zeolites.

Note that tectosilicates can only have additional cations if some of the silicon is replaced by a lower-charge cation such as aluminium, to give a negative charge overall. This substitution can also take place in other types of silicate. Olivine basalt The mineral olivine is a magnesium iron silicate with the formula (Mg,Fe)2SiO4. ... Epidote from Slovakia Epidote is a calcium aluminium iron sorosilicate mineral, Ca2(Al, Fe)3(SiO4)3(OH), crystallizing in the monoclinic system. ... The tourmaline mineral group is chemically one of the most complicated groups of silicate minerals. ... Figure 1:Mantle-peridotite xenolith with green peridot olivine and black pyroxene crystals from San Carlos Indian Reservation, Gila Co. ... For the logical fallacy, see Amphibology. ... Rock with mica Mica sheet Mica flakes The mica group of sheet silicate minerals includes several closely related materials having highly perfect basal cleavage. ... The Gay Head cliffs in Marthas Vineyard are made almost entirely of clay. ... Quartz is one of the most common minerals in the Earths continental crust. ... Feldspar is the name of an important group of rock-forming minerals which make up perhaps as much as 60% of the Earths crust. ... Zeolite Zeolites (Greek, zein,to boil;lithos,a stone) are minerals that have a porous structure. ... General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13, 3, p Appearance silvery Atomic mass 26. ...


Some rare minerals have more than one type of anion coexisting in their crystal structures, or complex-shaped anions that are intermediate between the simple types above.


  Results from FactBites:
 
Silicate Structures, Olivines, Garnets, & Aluminosilicates (1029 words)
In order to discuss the silicates and their structures it is first necessary to remember that the way atoms are packed together or coordinated by larger anions, like oxygen depends on the radius ratio of the cation to the anion, Rx/Rz.
Thus, this group is often referred to as the island silicate group.
In this case the basic structural group is Si The micas, clay minerals, chlorite, talc, and serpentine minerals are all based on this structure.
  More results at FactBites »

 
 

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