Silicate mineral group

 The Silicate Group

The silicate mineral group is of the most important because they continue about 90% of the earth's crust, occurring as the major constituents of most igneous rocks and in appreciable quantities in sedimentary( except limestone) and metamorphic varieties as well.  most common silicate mineral are made up chiefly of a few of the following 9 element Na, K, Al, Mg, Fe, Li, Si and O. These include minerals such as quartz, feldspar, mica, amphibole, pyroxene, olivine, and a great variety of clay minerals.

 Every Silicate mineral contains Oxygen and Silicon. The basic unit in all silicate mineral is the Silicon-oxygen tetrahedron. The silica tetrahedron, a combination of four oxygen atoms and one silicon atom. These are arranged such that planes drawn through the oxygen atoms form a tetrahedron. Since the silicon ion has a charge of +4 and each of the four oxygen ions has a charge of –2, the silica tetrahedron has a net charge of –4.

Type	Similar names	Ratio	Examples
Nesosilicates	orthosilicates, independent tetrahedra or island silicates	Si:O = 2:7	olivevin Zircon gypsum kyanite
Cyclosilicates	Ring silicates	Si:O = 1:3	Beryl and tourmaline ( all hexagonal system)
Inosilicates	Chain silicates	Single chain Si:O = 1:3 Double chain Si:O = 4:11	single chain pyroxenes, Asbestos Double chain Enstalite, Amphiboles
Phyllosilicates	Sheet silicates	Si:O = 2:5	Mica, chromite and kaolinite (Al  is an imp.)
Tectosilicates	Framework silicates and network structure	Si:O = 1:2	Quartz feldspar and felspathoid