Silicate is an anion consist of silicon and oxygen. Its general formula is (SiO.4-x)n. Silicate mineral is composed of silicate groups. Silica sand or quartz sand is silica ore. These are rock-forming minerals. It consists of SiO4-4 tetrahedra. In silicates only Si-O bonds are present. The hybridization of silicon in silicate is sp3. The Si is present at the centre of the tetrahedra with oxygen occupying the four corners of the tetrahedra.
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Silica is a crystalline polymer. It is a giant molecule with a tetrahedral SiO4-4 monomer. The silica monomer unit polymerizes through the Si-O-Si bonds. The oxygen atom is surrounded by two silicon atoms. The hybridization of silicon in silica is sp3. In the silica structure, silicon is present at the centre of the tetrahedral unit.
1. Orthosilicates Mineral
It is represented by SiO4-4. These contain discrete SiO4-4 tetrahedra. The corner in Orthosilicates is not shared.
Examples of orthosilicate mineral are willemite (Zn SiO4) and olivine (MgSiO4). These type of silicates are formed by metals. Therefore, also known as metal silicates.
2. Pyro Silicate
It is represented as Si2O7-6. It is also known as soro-silicate or disilicate. In this type of silicate two tetrahedra units are joined together by sharing one oxygen. These are also called island silicates.
Examples of pyro silicate mineral are Thortveitite (Si2 (Si2O7)) and hemimorphite (Zn4(OH)2 (Si2O7). H2O).
3. Cyclic or Ring Silicates
It is represented as (SiO3-2)n. In this type of ring silicates, two oxygen atoms per tetrahedron are sharing to form closed rings.
Examples of cyclic or ring silicate minerals are wollastonite Ca3(Si3O9) and benitoite BaTi (Si3O9).
4. Chain Silicates
It is represented as (SiO3)n-2n. These type of silicates are also known as Ino-silicates, metasilicates, pyroxenes, linear silicates. When two oxygen atoms are being shared with two tetrahedra to form a chain.
Example of chain silicates are: spodumene (Li Al (SiO3)2) and diopside (Ca Mg (SiO3)2)
Double chain silicates are also formed, by joining two chains. These type of silicates are called amphiboles.
Examples of double chain silicate minerals are tremolite (Ca2 Mg5 (Si4O11)2 (OH)2), asbestos.
5. Sheet Silicates
These type of silicates are also known as Phyllosilicates. These are formed by sharing three bridging oxygen per silicon atom. So a two-dimensional sheet is formed.
Structure of sheet silicates.
In the structure of sheet silicates, three oxygen of tetrahedra is being shared. So there is one unit negative charge per tetrahedral. This negative charge is neutralised by cations between the sheets.
Examples of sheet silicates are mica, clay, talc, and muscovite.
6. Three-dimensional Silicates-
It is represented as (SiO2)n. When all the four corners oxygen atom of tetrahedra are shared, a three-dimensional network of silica is formed. These type of silicates are neutral.
Examples of such silicates are quartz and tridymite.
What is Silica Rock?
Silica rock is a type of sedimentary rock. It is composed of silica dioxide, commonly known as silica. In silica rock, silica exists in the crystalline form like quartz or an amorphous form like cristobalite. The common rock of silica is known as chert.
Use of Silicates
Silica used in making concrete material like glasses.
It is used in making silica refractive bricks.
It is used in making abrasive material. These materials are used for grinding, polishing, and cleaning.
Silicates are used in making prism, eyeglasses, and cuvette.
It is used in making different types of laboratory apparatus.
Did You know?
Chert rock is a type of microcrystalline rock, which is composed of chalcedony and quartz.
Chert rock is the second most abundant precipitated rock.
The most abundant chemically precipitated rock is limestone.
Quartz is the purest form of silica.
Silica rocks are sedimentary rocks.