Structural Principles
In the vast majority of silicates, including silicate minerals, the Si occupies a tetrahedral environment, being surrounded by 4 oxygen centres. In these structures, the chemical bonds to silicon conform to the octet rule. These tetrahedra sometimes occur as isolated SiO44- centres, but most commonly, the tetrahedra are joined together in various ways, such as pairs (Si2O76-) and rings (Si6O1812-). Commonly the silicate anions are chains, double chains, sheets, and three-dimensional frameworks. All such species have negligible solubility in water at normal conditions.
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