Clay refers to an earthy substance that is composed of very tiny particles of rock that has been weathered. It also consists of different minerals, including illite, montmorillonite, attapulgite, and kaolinite. The mentioned minerals are made up of silica and alumina, as well as iron, sodium, calcium, and magnesium.
The small particles of clay have a diameter of around 0.004 mm, and is even smaller compared to particles of sand. Clay that is dry normally feels oily and is powdery when they are rubbed. However, when clay is combined with water, it can easily be molded.
Small quantities of clay are important for good soil because it can retain water and other essential substances that play important roles in the growth of plants. On the other hand, too much of it can make the soil too stiff and difficult to cultivate. The soil with large amounts of clay can be described as rock-like when it is dry, and too sticky when it is wet.
There are two types of clay, namely sedimentary and residual. The former refers to the type which is formed when the tiny particles of rocks that have been weathered are transported (usually by water streams) from their place of origin to another place where it will be deposited. This sedimentary type of clay usually comes in layers. The other type called residual clay directly comes from the rock that is weathering. This type of clay is formed when the small particles of these weathering rocks are combined with water and other materials that are found in the surrounding soil.
Clay can also be categorized depending on its properties and composition. It can be classified as common clay, fire clay, bentonite, ball clay, fuller’s earth, and kaolin. Generally, the major uses of clay are in the field of pottery and ceramics making.