THE DEFINITION AND NOMENCLATURE OF HALLOYSITES

Abstract--This review of the literature shows that there have been many attempts to modify or revise the original definition of halloysites as distinguished from kaolinites, which was based on the greater water content of the halloysites. In general; these various attempts have arrived at definitions of halloy-sites as distinguished from kaolinites that are based on one or more particular instrumental or chemical techniques. Further investigations with almost all of these techniques have shown the apparently clear distinctions of this kind to be misleading. All such instrumentally--or chemically--based definitions were shown to either complicate and confuse the distinction between halloysites and kaolinites or to provide only empirical and subtle distinctions. It is concluded that only the original definition, with slight adaptations, enables clear and unambiguous distinctions to be made between halloysites and kaolinites. It is noted, however, that a distinctive structure for halloysite has been postulated as a result of electron diffraction studies. Further studies of this kind could well establish such a structure as being definitive of the mineral species. The literature also reveals a long-standing disagreement over the nomenclature of different forms of halloysite and particularly over the nomenclature of and distinction between the two forms of halloysite at the extreme nds of the hydration series. An analysis of experimental studies of th