Bentonites. Geology, mineralogy, properties and uses / Бентониты. Геология, минералогия, свойства и использование

The name bentonite was suggested in 1898 by Knight for a peculiar claylike material with soapy properties from its occurrence in the Fort Benton unit of Cretaceous age formations in Wyoming (U.S.A.). Hewitt (1917) and Wherry (1917) first established that this particular clay is an alteration product of volcanic ash, although an earlier observation by Condra (1908) suggested this origin for a similar clay from northern Nebraska. Ross and Shannon (1926) presented the following definition which has been widely quoted: “Bentonite is a rock composed essentially of a crystalline clay-like mineral formed by the devitrification and the accompanying chemical alteration of a glassy igneous material, usually a tuff or volcanic ash”. These authors further stated that, “the characteristic clay mineral has a micaceous habit and facile cleavage, high birefringence, and a texture inherited from thevolcanic tuff or ash, and it is usually the mineral montmorillonite, but less  often beidellite”. The term bentonite is now well established (Wright, 1968) for any clay which is composed dominantly of a smectife clay mineral, and whose physical properties are dictated by this clay mineral; this is the definition used in this volume. <...>