Silicate
From Freepedia
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 acids.
In common conditions, the most stable form is silicon dioxide, SiO2, often called quartz, and similar species. This always has, in equilibrium, a minute amount of silicic acid, H4SiO4. Chemists consider quartz as insoluble, but it moves around at longer timescales. Also, in basic conditions, we find H2SiO42-.
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:
- Olivine (single tetrahedron) - Nesosilicates
- Epidote (double tetrahedra) - Sorosilicates
- Tourmaline (rings of tetrahedra) - Cyclosilicates
- Pyroxene (single chain) - Inosilicates
- Amphibole (double chain) - Inosilicates
- Micas and clays (sheet) - Phyllosilicates
- Feldspars (framework) - Tectosilicates
- Quartz (SiO2 framework)
Silicate was also the name given to the bone-sucking monsters in the British horror movie Island of Terror (aka Night of the Silicates). These were silicon-based organisms created by cancer research gone wrong, which consumed the calcium phosphate in the bones of carbon-based lifeforms.
