Introduction
What are Silicates?
A member of an ionic compound found in the anion family and containing oxygen and silicon. Silicates are formed from groups of silicates and form rocks. They are the most abundant minerals in the earth's crust, making up 90% of the crust. Due to rework and formation processes, various silicate minerals occur in great combinations on Earth. The processes are diagenesis, weathering, splitting, melting, metamorphosis and crystallisation.
The minerals found on Earth are concentrated by the silicon atom of the tetrahedron, on which are four atoms of covalent oxygen. Additionally, silicates of minerals are grouped into seven groups based on the composition of the silicate ion.
Types of Silicates: Major groups include nesosilicates, sorosilicates, cyclosilicates, inosilicates, phyllosilicates, and tectosilicates.
Types of Silicates
The silicate tetrahedral units consist of silicon and oxygen-containing minerals linked together in multiple patterns. Based on how the tetrahedral units are joined, silicates are classified into the following types:
1. Orthosilicates (or Nesosilicates)
2. Pyro silicate (or Sorosilicates)
3. Cyclic silicates (or Ring silicates)
4. Chain silicates (or pyroxenes)
5. Amphiboles
6. Sheet or phyllosilicates
7. Tectosilicates
Amphibole Silicate Minerals
Uses of Silicates
Uses of Silicates in Industries like glass, ceramic, cement, etc.
Glass manufacturing: Glass is made from silicate. This is one of the major and most productive uses of silicate. Formless and hard materials such as clay or sand are burned at high temperatures. The material formed after heating is malleable, so glasses can be made for drinking.
The use of silicates in ceramics: Silicates are used to make ceramics. Ceramics made of silicate have thermal characteristics. Therefore, they are a major advantage in the engineering and technology industries. In one such example, the spacecraft uses ceramic silicate tiles as a barrier from intense atmospheric temperatures. Silicates also benefit borehole walls when drilling to prevent the walls from cracking.
Use of Silicates in Ceramics
Microchips: Microchips are a form of silicon cut into small proportions that have controlled printed orders through photographic processes. Silicates have unique properties, for example, producing thermal insulation, conducting electricity, providing a high-frequency vibration, and being able to conduct electricity. The most central component of silicates is silicon. The crystal is very strong and can be cut into smaller sizes, thus conducting electricity. These properties make silicon the best material for making microchips, passing through computers, mobile phones and gaming devices.
Quartz Uses in Everyday Life
Quartz crystals are silicate with the unique ability to produce a rhythmic high-frequency vibration. For this reason, these crystals are used to make oscillators used in clocks, radios and pressure gauges. The crystal emits a rhythmic beat that when connected to an electronic source and movement pieces can be logged, usually in the form of megahertz (MHz), which is 1 million cycles per second. In the example of a watch, the rhythmic beat of the crystal moves the other hand. Quartz crystals are also used in mysticism.
Quartz Crystals
Why are the Silicates Important?
Silicates occupy about per cent of the Earth's crust and upper mantle, as a major component of most igneous rocks and also in appreciable amounts in sedimentary and metamorphic types. They are also important components of lunar samples, meteorites and most asteroids.
Solved Questions
1. Write the three most important types of Silicates.
Ans: Three important types of Silicates are:
Orthosilicates (or Nesosilicates)
Pyro silicate (or Sorosilicates)
Cyclic silicates (or Ring silicates)
2. Write one use of Quartz crystals.
Ans: Quartz crystals are used to make oscillators in clocks, radios and pressure gauges.
Learning by Doing
Write True or False.
Glass is made from silicate.
Silicates are the minerals found on Mars.
Quartz crystals are used in mysticism.
Orthosilicates are ring silicates.
Summary
As we have already read this chapter thoroughly, now we know the actual meaning of silicates and understand their uses and importance in our life. There are many types of silicates found. Some of them are mentioned in this chapter. We have also explained Quartz uses in a separate heading.
FAQs on What are Silicates?
1. What exactly are silicates in the context of chemistry?
Silicates are a very large and important class of minerals that constitute the majority of Earth's crust. Chemically, they are compounds containing silicon and oxygen atoms. The fundamental building block of all silicates is the [SiO₄]⁴⁻ tetrahedron, which consists of a central silicon atom covalently bonded to four oxygen atoms.
2. What is the basic structural unit of all silicates and its chemical formula?
The basic structural unit for every silicate is the silicate anion, [SiO₄]⁴⁻. This unit is shaped like a tetrahedron, with a silicon (Si) atom at the center and four oxygen (O) atoms at the corners. The overall charge of this independent unit is -4.
3. What are the main types of silicates based on their structure?
Silicates are classified into several types based on how the [SiO₄]⁴⁻ tetrahedra are linked together by sharing oxygen atoms. The main types are:
- Orthosilicates (Nesosilicates): Discrete [SiO₄]⁴⁻ tetrahedra.
- Pyrosilicates (Sorosilicates): Two tetrahedra sharing one oxygen atom.
- Cyclic Silicates (Ring Silicates): Tetrahedra linked in a ring, each sharing two oxygen atoms.
- Chain Silicates (Inosilicates): Tetrahedra linked in a linear chain, including single and double chains.
- Sheet Silicates (Phyllosilicates): Tetrahedra linked in a two-dimensional sheet, each sharing three oxygen atoms.
- Three-dimensional Silicates (Tectosilicates): A 3D framework where each tetrahedron shares all four oxygen atoms.
4. How does the sharing of oxygen atoms determine the classification of silicates?
The classification of silicates is fundamentally determined by the number of shared oxygen atoms per [SiO₄]⁴⁻ tetrahedron. When tetrahedra do not share any oxygens, they are discrete units (orthosilicates). As they share more oxygen atoms—one, two, three, or all four—they form progressively more complex structures like pairs, chains, sheets, and finally, a complete three-dimensional network. This sharing reduces the overall oxygen-to-silicon ratio and defines the properties of the resulting mineral.
5. What is the key structural difference between single-chain (pyroxenes) and double-chain (amphiboles) silicates?
The key difference lies in their assembly. Single-chain silicates (pyroxenes) are formed when each tetrahedron shares two of its oxygen atoms to form a long, simple chain with the general formula (SiO₃)n²ⁿ⁻. In contrast, double-chain silicates (amphiboles) are formed when two single chains are linked together side-by-side by sharing additional oxygen atoms, resulting in a more complex structure with the general formula (Si₄O₁₁)n⁶ⁿ⁻.
6. Why are three-dimensional silicates like quartz so hard and chemically stable?
Three-dimensional silicates, also known as tectosilicates, like quartz (SiO₂), are exceptionally hard and stable because all four oxygen atoms of each tetrahedron are shared with neighbouring tetrahedra. This creates a strong, continuous, and rigid 3D covalent network throughout the entire crystal. Breaking these strong Si-O bonds requires a large amount of energy, which translates to high hardness, high melting points, and low chemical reactivity.
7. What are some important examples and uses of silicates in industry and daily life?
Silicates are essential in many applications due to their diverse properties. Some common examples and uses include:
- Quartz: Used in glassmaking, electronics (as piezoelectric material), and as a gemstone.
- Feldspar: A key ingredient in ceramics and glass manufacturing.
- Zeolites: Used as catalysts in the petroleum industry and as water softeners in detergents.
- Talc and Mica: Used in cosmetics, paints, and as industrial lubricants due to their sheet-like structure.
- Cement: Primarily composed of calcium silicates, forming the backbone of modern construction.
