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silicates

The Silicates are the largest, the most interesting, and the most complicated class of minerals by far. Approximately 30% of all minerals are silicates and some geologists estimate that 90% of the Earth's crust is made up of silicates. With oxygen and silicon the two most abundant elements in the earth's crust, the abundance of silicates is no real surprise.

The basic chemical unit of silicates is the (SiO₄) tetrahedron shaped anionic group with a negative four charge (-4). The central silicon ion has a charge of positive four while each oxygen has a charge of negative two (-2) and thus each silicon-oxygen bond is equal to one half (1/2) the total bond energy of oxygen. This condition leaves the oxygen with the option of bonding to another silicon ion and therefore linking one (SiO₄)) tetrahedron to another and another, etc.

 There are Orthosilicates,

Example:phenacite, Be₂SiO₄ and willemite, Zn₂SiO₄

Pyrosilicates:

Thortveitite, Sc₂Si₂O₇ is a pyrosilicate

Ring and chain silicates: Benitoite BaTi(SiO₃)₃

_{Double chain silicates, Silicates with sheet structure etc.}