As industrial minerals, clays are a complex group that consists of several mineral commodities, each having some-what different mineralogy, geologic occurrence, technology, and uses. In this section, these commodities are organized as follows: (1) bentonite and fuller's earth; (2) kaolin, ball clay, halloysite, and refractory clays; and (3) miscellaneous clay and shale. Bentonite and fuller's ... [Show full abstract] earth are grouped together because they are closely interrelated. Though bentonite is a term based on mineral composition and fuller's earth is a term based on use, the two are virtually inseparable, because much clay sold as fuller's earth is actually bentonite. Kaolin, ball clay, halloysite, and refractory clays are grouped together because they consist mainly of minerals of the kaolin group. Miscellaneous clay and shale is a grouping of several fine-grained materials referred to as common clay.