ABSTRACT
The term clay (or clays) is used in soil science to describe any naturally occurring inorganic materials composed primarily of fine-grained minerals of particle size less than 2 jim. The term clay minerals refers to a specific group of layer-type aluminosilicate minerals, which contain structural hydroxyl groups and belong to the general class of phylosilicates [1]. They are very fine particles or crystals, often colloidal in size, and usually plate-like in shape, less commonly tabular or scroll shaped. Because of their fineness they have the surface chemical properties of colloids. Due to their overwhelming diversity, their struc tural properties, chemical composition, and related unique surface chemical properties, clay minerals are fascinating colloid systems, which have been studied extensively from various aspects and for various purposes.
