Skip to main content

Silicates

Introduction: Silicates are a fascinating and diverse group of minerals that form the foundation of the Earth's crust. They are composed of silicon and oxygen, the two most abundant elements in the Earth's crust. Silicates exhibit a wide range of chemical compositions and crystal structures, making them crucial components of rocks, soils, and various industrial applications.

The fundamental unit in the building of silicate minerals is the SiO4-4 tetrahedron in which the silicon atom is situated at the centre of tetrahedron where corners are occupied by four oxygen atoms.
The radius ratio of Si+4 to O-2 requires that Si+4  be coordinated by 4 O-2 ions in tetrahedral coordination.
In order to neutralize the +4 charge on the Si cation, one negative charge from each of the Oxygen will reach the Si cation. Thus each Oxygen will be left with a net charge of -1, resulting in a SiO4-4 tetrahedral group that can be bond to other cations. It is this SiO4-tetrahedron that forms the basis of the silicate minerals.

1. Nesosilicate/Orthosilicate/Independent silicate/Island silicate
Corner oxygen are not shared with other SiO⁴ tetrahedra, each tetrahedron will be isolated.
Silicate unit- SiO4-4
Si:O ratio- 1:2
No. Of oxygen shared- 0
Example- Garnet, zircon, kyanite, olivine
Nesosilicate

2. Sorosilicate/Paired silicate structure
In this one of the corner oxygen is shared with another tetrahedron.
Silicate unit- Si2O7-6
Si:O ratio- 2:7
No. Of oxygen shared- 1
Example- Epidote, pumpellyite, lawsonite, vesuvianite
Sorosilicate

3. Cyclosilicate/Ring structure
Two of the oxygen are shared with the neighbouring tetrahedra, structure resulting in the form of ring.
Silicate unit- Si6O18-12
Si:O ratio- 1:3 
No. Of oxygen shared- 2
Example- Beryl, tourmaline, axnite
Cyclosilicate: 3 and 4 member ring tetrahedra sharing 2 oxygen

4. Inosilicate:
(A) Single Chain
A linkage of tetrahedra similar to that of the ring silicates i.e, sharing two of the oxygen in such a way so as to form a long single chain of linked SiO⁴ tetrahedra.
Silicate unit- Si2O6-4
Si:O ratio- 1:3 
No. Of oxygen shared- 2
Example- Pyroxene, spodomene
Single chain structure sharing 2 oxygen

(B) Double chain structure
If two chains are linked so that each tetrahedra shares 3 oxygen so as to form double chain structure.
Silicate unit- Si4O11-6
Si:O ratio- 4:11
No. Of oxygen shared- 2 and 3
Example- Amphibole
Double chain structure sharing 2 and 3 oxygen

5. Phyllosilicate/Sheet silicate
If 3 of the oxygen shared and extend indefinitely in two dimensional network bor sheet.
Silicate unit- Si4O10
Si:O ratio- 2:5
No. Of oxygen shared- 3
Example- Mica, lepidolite
Each tetrahedra sharing 3 oxygen

6. Tectosilicate/3 D framework silicate
If all the corner oxygen are shared with tetrahedra to develop framework structure.
Silicate unit- SiO2
Si:O ratio- 1:2
No. Of oxygen shared- 4
Example- Quartz, feldspar, feldspathoid 
Tectosilicate

Significance of Silicates: Silicates play a vital role in shaping the Earth's crust and have immense economic importance. They are integral components of rocks, such as granite, basalt, and shale, contributing to their properties and characteristics. Additionally, silicates are essential in the formation of soil, influencing its fertility and composition.

Beyond geological significance, silicates have numerous practical applications in various industries. From construction materials like cement and concrete (which often contain silicate minerals) to ceramics, glass manufacturing, and even the production of detergents and cosmetics, silicates are omnipresent in our daily lives.

Conclusion: Silicates form the backbone of the Earth's geology and are an indispensable part of our everyday existence. Their diverse types and widespread applications underscore their significance in various fields. Understanding silicates allows us to appreciate the complexity of the Earth's composition and the impact they have on our world. So, the next time you encounter a beautiful gemstone, sturdy construction material, or a glass window, remember that you are witnessing the fascinating influence of silicates in action.

Comments

Post a Comment

Popular posts from this blog

CIPW NORMS CALCULATIONS

CIPW NORMS CALCULATIONS The CIPW norm is named after the four petrologists, Cross, Iddings, Pirsson and Washington, who devised it in 1931. What is a Norm and why it is needed? A norm is a means of converting the chemical composition of an igneous rock to an ideal mineral composition. It often reveals similarities in rocks that have quite different modes, or observed mineral assemblages. Some of the factors that can cause such variations are: • Disequilibrium (for example, zoned minerals or reaction rims isolating the interiors of grains) • Temperature • Pressure • Alteration • Water content (otherwise identical rocks might contain biotite, amphibole, or pyroxene, depending on water content) • Other minor constituents. For example, excess sulfur or chlorine might cause scapolite to form instead of feldspar. Boron typically causes tourmaline to form. The CIPW norm calculates mineral composition as if the magma were anhydrous (water is simply treated as a separate phase) and at low press...
Post a Comment
Read more

Branches Of Geology

1. Mineralogy-                       Mineralogy defined as the offshoot of geology dealing with the scientific analysis of the minerals, including chemistry, structure, physical and optical properties and its artifacts. 2. Structural Geology-                                   The   branch of geology dealing with the three-dimensional distribution of the rock and its deformational history.  3. Oceanography-                             The discipline of geology dealing with the studies of oceans and seas including their framework, physical and chemical properties, origin and its ancient history and current direction.  4. Petrology-                     Petrology is systematic studies of rocks, their origin, structure, c...
Post a Comment
Read more

FOSSILISED LEAVES FROM JURASSIC PERIOD IN JHARKHAND

 Geologists Discover Fossilised Leaves From Jurassic Period in Jharkhand Geologists have found fossilised leaves, estimated to be around 150-200million years old, in Jharkhand's Sahibganj district. A couple of 20 cm by 5 cm fossilised leaves of genus Ptilophyllum have been found in Dudhkol mountain in Taljhari area on 26/09/2020 and further excavation is underway, lead geologist assistant professor Ranjit Kumar Singh of Sahibganj PG College said. The excavation is being conducted in association with National Botanical Research Institute, Lucknow under a project of the Department of Science and Technology of the Union government. "Such leaves were consumed by herbivorous dinosaurs. Smaller fossils from Upper Jurassic to Cretaceous period were earlier found in the region. We might even find fossilised dinosaur eggs during further excavation," Singh told .
Post a Comment
Read more