What is Clay and where does it come from? Properties Of Clay. Is Clay a mineral? What is the chemical equation of Clay? What is the composition of Clay?

Clay

The term clay is applied to those fine grained earthy materials composed of various minerals whose most prominent properties are:    

1. Plastic when wet,
2. Capable of retaining of shape when dried,
3. Formation of a hard rock-like mass without losing the originals contour when heated to red heat.

Formation: Clay is decomposed products of the igneous rocks containing mainly alumina and silica, which by the action of the weathering agencies are converted into plastic or semi plastic masses. When the parent rock contain impurities like lime magnesia, iron etc, the final products are the impure clays, but if the disintegration takes place from feldspathic rock the residual clays are comparatively pure and we get white clay known as Kaolin. The precise manner in which this decomposition occurs is still open to investigation. The basic rocks from which clays are formed are complex aluminosilicates. During the weathering this becomes hydrolysed, the alkali and alkaline earth ions from soluble salts and are leached out. The remainder consists of hydrated aluminosilicates of varying composition and structure and silica. The liberated silica is probably hydrated and ultimately converted into crystalline form.

This process can be represented by the following chemical equations:    
  

Hydrolysis: K2O.Al2O3.6SiO2 + H2O => Al2O3.6SiO2 + K2CO3

Desilication: Al2O3.6SiO2 => Al2O3.2SiO2 + 4SiO2

Hydration:  Al2O3.6SiO2 + H2O => Al2O3.2SiO2.2H2O

K₂O.Al₂O₃.6SiO₂ + 2H₂O => Al₂O₃.2SiO₂.2H₂O +K₂CO₃ + 4SiO₂

Click on the image for the best view