· The definition of clay raises the important issue of clay constituents and, implicitly, the definition of 'clay mineral'. Mackenzie (1963, p. 15) noted the inappropriateness of defining clay mineral as "any mineral which occurs in clay" since, among several reasons, it would include many accessory minerals that are not characteristic of clay.
FOR MINERALS THE ROLE OF CLAYS IN FIXING LITHIUM By HARRY C. STARKEY ABSTRACT Lithium, in small amounts, is widespread in clay minerals. It may be present in clays as impurities, as inclusions, in lattice cavities, adsorbed on the surface, or by isomorphous substitution. Isomorphous substitution is the most common occurrence. The clay contain