Kaolin or China clay, is nearly white in color. It is distinguished from other industrial clays based on its fine grained plate like particle size, plasticity and pure coloring. Its ability to disperse in water make it an ideal pigment.
The primary constituent in kaolin is the mineral kaolinite, a hydrous aluminum silicate formed by the decomposition of minerals such as feldspar. Chemical formula of kaolin is H2Al2Si2OK8-H2O.
The white color of the mineral can either be naturally occurring, or can result after processing by removing clay particles from silica & other compounds by sedimentation process. Kaolin deposit consists of various types of raw kaolin having yield content from 8 to 30% of clay particles rest being silica sand. The small particle size of the clay contributes to its white color by scattering light.
Although kaolin is found throughout the world, deposits with suitable whiteness, plasticity, viscosity and other favorable characteristics are rare. Ironically, the one of the best deposits are located in India.