Kaolinite

Article By:

Kogel, Jessica Elzea Thiele Kaolin Company, Sandersville, Georgia.

Last reviewed:November 2019

DOI:https://doi.org/10.1036/1097-8542.361900

A common hydrous aluminum silicate mineral found in sediments, soils, hydrothermal deposits, and sedimentary rocks. It is a member of a group of clay minerals called the kaolin group minerals, which include dickite, halloysite (7 Å and 10 Å), nacrite, ordered kaolinite, and disordered kaolinite. These minerals have a theoretical chemical composition of 39.8% alumina, 46.3% silica, and 13.9% water [Al₂Si₂O₅(OH)₄], and they generally do not deviate from this ideal composition. They are sheet silicates comprising a single silica tetrahedral layer joined to a single alumina octahedral layer. Although the kaolin group minerals are chemically the same, each is structurally unique as a result of how these layers are stacked on top of one another. Kaolinite is the most common kaolin group mineral and is an important industrial commodity used in ceramics, paper coating and filler, paint, plastics, fiberglass, catalysts, and other specialty applications. See also: Clay minerals; Silicate minerals

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