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Asit Roy | asitroy

What are Clay Minerals?

Aug 20th 2015 at 11:37 PM

Definition

Clay is one of the soil separates, an important mineral component of soil. They are the most important chemical weathering product of the soil containing significant amounts of alkali metals, iron and alkaline earths. Research has found clay minerals are composed of silica, alumina or magnesia or even both.

Origin

Clay can be found in nature as well as certain types of clay minerals can be synthesised.

  • Nature

In nature, clay is formed out of natural weathering processes which are determined by a few factors namely, the nature of the parent rock, climatic conditions, vegetation, time period, etc. Development of clay minerals by natural hydrothermal processes requires the presence of alkalis and alkaline earths.

  • Synthetic

Clay minerals can be synthesised at normal temperature and pressure by way of mixing the reactants slowly and then diluting them to a great extent. Clay minerals of some types can also be combined by way of chemical treatments. For example vermiculite can be formed by an elongated process in which mica is combined with hydrated alkali.

Occurrence

All types of clay materials have been reported to occur in soil. Clay minerals like Allophane, imogolite and hydrated halloysite are the essential components in ando soils (soils developed on volcanic ashes).

Whereas dominant components like vermiculite, chlorite and smectite are found in podzolic soils. Kalinite and sepiolite are predominantly found in lateritic soils.

Structure

The basic structure of clay minerals is in the ratio of 2:1, that is, two silicon tetrahedral layers and one aluminium octrahedral layer.

Clay minerals are basically composed of two basic building blocks, namely Silicon-oxygen tetrahedron and Aluminium octahedral.

In Tetrahedron sheets, every individual tetrahedrons share three out of four oxygens. They are arranged in such a manner that hexagonal patterns are linked with basal oxygens and the apical ones point up or down.

Octahedral sheets are made up of individual octahedrons that share the portions of oxygen with Aluminium, Magnesium and Iron. Even these octahedral sheets are constructed in a hexagonal pattern, also known as a gibsite sheet.

Properties

The properties of clay minerals are as follows.

  • Clay minerals are extremely small for measuring optical properties. They tend to form microscopic crystals.
  • Mild changes in weather and humidity can make clay minerals water absorbent.
  • Once mixed with water, they can be moulded to give new forms and shapes. Also, there is expansion because water fills up the empty spaces left in between the layers.
  • When heated at temperatures, the structure gets destroyed depending on the composition of the substance.
  • Solubility of clay materials varies in acids, depending upon the nature, temperature, duration and concentration of both, acid and clay.

KPL International Ltd is the largest Kaolin Clay Supplier of India. In the last two decades KPL has stood up to the position of marketing quality products in India, satisfying thousands of customers in throughout the world.

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