Clays and Clay Minerals in Natural and Synthetic Systems

The study of clay minerals and clay assemblages has been and still
is, for that matter, greatly hampered by the innate character of a
material which, by its definition, is of small particle size. Little
things are at times easier to study than big ones as witnessed by the
immense advances in nuclear physics. 1lowever.in the case of natural
silicates this is not true. Since the material has a small grain size,
different phases can be easily mixed mechanically, making it difficult to
separate them physically one from the other and difficult to identify them
optically since their diameter approaches the limit of common optical
resolution. One is left with X-ray diffraction or techniques which deal
with energy absorption by a crystalline structure as means of investigation. Since these methods have only recently become commonly available
to geologists and mineralogists, much of the pertinent information on
clay minerals is still relatively new. A parallel interest has developed
in experimental silicate phase equilibria concerning phyllosilicates in
recent years which has allowed development of systematics in mineral stability studies.