Clay

Clay is a fine-grained sediment composed of extremely small particles (with grain sizes below a specific threshold). It consists largely of minerals known as clay minerals, which are layered in structure. When water is added, clay becomes plastic and can be shaped; when it dries or is fired, it hardens and retains its form.

Clay forms from the long-term weathering of rocks, particularly rocks containing feldspar minerals. Rain, heat, frost, and chemical weathering break down rock into fine particles. Rivers and wind then transport these particles and deposit them in valleys, basins, and on beaches, where they accumulate as clay.

Physical Properties

The most important property of clay is plasticity—the ability to be shaped without breaking. This comes from the structure of clay minerals and the water between their layers, which allows them to move relative to one another. Clay also does not allow water to pass through easily, making it useful for sealing water systems in wells and reservoirs.

Use in Pottery and Construction

Pottery made from clay is one of humanity's oldest technologies. A shaped pot is fired in a kiln at high temperature; the heat transforms the mineral structure of the clay, so the pot does not return to being clay when water is added. In construction, clay is used to make sun-dried bricks or fired bricks, and also for the traditional earth walls of houses in many parts of Somalia.

Agriculture

Soils with a high clay content retain water and nutrients well, but have poor aeration and can become hard when dry. Farmers often add compost or organic matter to loosen the soil and help plant roots penetrate. Soils with a balanced mixture of clay, sand, and silt are generally considered most suitable for farming.