[Chemistry Class Notes] on Silicate Mineral Pdf for Exam

Let’s talk about silicates in chemistry. Silicates are an anion that consists of both silicon and oxygen. The family of silicates consists mainly of orthosilicates, metasilicates, and parasilicates. The name is also used for any salt of such anions, for example, sodium metasilicate.

Silicate anions often are already polymeric molecules and they have an extensive variety of structures. Silicates in geology and anatomy mean silicate minerals, ionic solids with silicate anions, and rock salts that consist of these minerals predominantly.

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 [SiO{_{4}}^{4-}] tetrahedra. In silicates only Si-O bonds are present. The hybridization of silicon in silicate is [ sp^{3}]. The Si is present at the center of the tetrahedra with oxygen occupying the four corners of the tetrahedra.  

Sometimes some anions that do not fit in the formula that is mentioned above can also be called silicates, only if they have the presence of silicon. For example, hexafluorosilicate does not fit in the formula of these silicates but still, its anions, due to the presence of silicone, are referred to as silicates.

Silicate Structure

Silica is a crystalline polymer. It is a giant molecule with a tetrahedral [SiO{_{4}}^{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 [ sp^{3}]. In the silica structure, silicon is present at the center of the tetrahedral unit. 

Silica Types

1. Orthosilicates Mineral

It is represented by [SiO{_{4}}^{4-}]. These contain discrete [SiO{_{4}}^{4-}] tetrahedra. The corner in Orthosilicates is not shared.

Examples of orthosilicate minerals are willemite ([ZnSiO_{4}]) and olivine ([MgSiO_{4}]). These types of silicates are formed by metals. Therefore, also known as metal silicates.

2. Pyro Silicate

It is represented as [ Si_{2}O{_{7}}^{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 minerals are Thortveitite [(Si_{2} (Si_{2}O_{7}))] and hemimorphite [(Zn_{4}(OH)_{2} (Si_{2}O_{7}). H_{2}O)].

3. Cyclic or Ring Silicates

It is represented as [(SiO{_{3}}^{2-})]n. In this type of ring silicates, two oxygen atoms per tetrahedron are shared to form closed rings. 

Examples of cyclic or ring silicate minerals are wollastonite [Ca_{3}(Si_{3}O_{9})] and benitoite BaTi ([Si_{3}O_{9}]).

4. Chain Silicates

It is represented as [(SiO_{3})_{n – 2n}]. These types 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.

Examples of chain silicates are spodumene (Li Al [(SiO_{3})_{2}]) and diopside (Ca Mg [(SiO_{3})_{2}])

Double chain silicates are also formed, by joining two chains. These types of silicates are called amphiboles.

Examples of double chain silicate minerals are tremolite [(Ca_{2}Mg_{5}(Si_{4}O_{11})_{2} (OH)_{2})], asbestos.

5. Sheet Silicates

These types 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 tetrahedra oxygen is being shared. So there is one unit negative charge per tetrahedral. This negative charge is neutralized by cations between the sheets.

Examples of sheet silicates are mica, clay, talc, and muscovite.

6. Three-dimensional Silicates- It is represented as [(SiO_{2})_{n}]. When all the four corners of the oxygen atom of tetrahedra are shared, a three-dimensional network of silica is formed. These types of silicates are neutral. Silicate minerals that contain the three-dimensional framework are known as tectosilicates. Perhaps, they are the most structurally complicated silicates, being those that have silicon and oxygen networks that can extend into any three-dimensional area.

Examples of such silicates are quartz and tridymite. Feldspar is the most famous of them all.

Examples of Such Silicates are Quartz and Tridymite

What is Silica Rock?

Silica rocks are the type of sedimentary rocks that largely consists of silica dioxide. These silica rocks can occur or exist either in the form of quartz or as amorphous silica and cristobalite. It basically includes the rocks that are formed as chemical precipitates and it excludes the rocks whose origin is either detrital or fragmental. Siliceous Rock is a good example of silica rock and the most common silica rock is known as chert.

 Uses of Silicates

• Silica is used in making concrete materials like glasses.

• The most common use of these silicates is that they can be used in making silica refractory bricks. They are extremely high-quality bricks.

• It is used in making abrasive material. These materials are used for grinding, polishing, and cleaning. 

• Silicates are used in making prisms, eyeglasses, and cuvette. It is used in making different types of laboratory apparatus.

• For diverse manufacturing, technological and artistic needs silicates are used as they are versatile materials that are both available naturally and artificially.

• Examples of natural silicates include graphite, gravel, and garnets.

• Examples of artificial silicates include Portland cement, ceramics, glass, and water glass.

Did You know?

• Chert rock is a type of microcrystalline rock, which is composed of chalcedony and quartz.

• Chert rock is mentioned as the second most abundant precipitated rock. Precipitated rock is the one that is formed by the precipitation of minerals from water.

• The most abundant chemically precipitated rock is limestone.

• Quartz is the purest form of silica.

• All the silica rocks are sedimentary rocks, sedimentary rocks are the ones that are formed by the accumulation of or deposition of minerals or organic particles at the surface of the earth.

Conclusion

If you are taking up chemistry, then learning about Silicate Minerals will help in the long term. has covered all points to learn.