Formation of clay minerals

Extract

Among early observers of the origin and occurrence of clay minerals were those geologists who described the hyarothermal alteration of felspar in granite to kaolinite and of some basic igneous rocks to fuller's earth. There were speculations into the origin of bauxite and laterite and of the effect of weathering on various rocks and minerals in different climates. Little progressr however, was made until clay minerals could be identified by X-ray diffraction and other methods.

Modern studies (Grim 1953) of the formation of clay minerals begin with Noll's hydrothermal synthesis of montmorillonite (1930), pyrophyllite, kaolinite, and mica (1936); since then, most of the clay minerals have been synthesised from their oxides, though attapulgite and hydrated halloysite have not yet been made in the laboratory. Even to-day not enough experimental observations have been made to allow really convincing phase-rule diagrams of these hydrated systems to be made.