Colloidal and Metacolloidal Sedimentary Minerals and their Origin

Abstract

Coagulates, i.e., sediments of colloidal solutions, may settle out in a fine-granular or a gelatinous form; the latter are called gels. The coagulates of lyophobic (and hydrophobic) colloids are fine-granular, rarely flocculent precipitates. In particular, coagulates of the hydrous oxides of iron and aluminum are generally flocculent. The coagulates of lyophilic (and hydrophilic) colloids are gelatinous or very bulky flocculent sediments. The gels of hydrophilic have a very high water content. Some substances, such as silica, may form either gelatinous or fine-granular coagulates, depending on the environment. The coagulation of hydrosols, widespread in nature, leads to the formation of hydrogels. Gelatinous (the first time) coagulates of lyophilic colloids are called actual gels or coagula; these arise by gelatinization of a solution, with no separation from the solvent. Coagulators may cause gelatinization (i.e., yield coagel) in inorganic colloids such as hydrous silica, aluminum hydroxide, etc. It is quite natural that the consistency of a gel depends on the content of water in it.