Coupon Accepted Successfully!


Silicates and Glass

The earth's crystal rocks and their breakdown products like clays, soils and sands, are mostly silicates and silica. Mica, asbestos, quartz, feldspar, zeolites, etc. are some of the important silicate minerals.
Basically all the silicates and silica contain tetrahedra. They differ only in the way the tetrahedra are linked together. They can be classified as given below.


These contain individual discrete tetrahedral (Fig. 12.12). Phenacite (Be2SiO4) and zircon(ZrSiO4) minerals provide examples of orthosilicates.



These contain discrete, ions are formed when one oxygen atom of two SiO4 tetrahedra is shared. Thorteveitite (Sc2Si2O7) is an example of the mineral containing ion.

Chain and Cyclic Silicates

In these silicates two oxygen atoms per tetrahedron are shared. The resulting structure may be the chain type or the cyclic type.

Sheet Silicates

Sheet Silicates

The sharing of three oxygen atoms by each tetrahedron giving an infinite two-dimensional sheet of the empirical formula forms these silicates, .

Three-dimensional Silicates

In these silicates, all the four oxygen atoms of a SiO4 tetrahedron are shared with other tetrahedra resulting in a three-dimensional lattice. In case there is no replacement of silicon by other metals, the resulting formula is SiO2 (quartz). Felspar, zeolites and ultramarines also belong to this class. In these silicate minerals, other metals replace some of the Si atoms.

Silica (SiO2) occurs both in the free and combined state in nature. In the free state it is found in several amorphous and crystalline forms.

Silica is extensively used in industry. It is used in the manufacture of glass, porcelain, sand paper, firebricks, sandstones, etc. Silica gel finds use as a desiccant and as a chromatographic support. Quartz (crystalline form of silica) glass is used in the manufacture of optical instruments, chemical apparatus, etc.

Test Your Skills Now!
Take a Quiz now
Reviewer Name