Any one of the crystalline metal aluminosilicates belonging to a class of minerals known as zeolites. These minerals are found widely scattered in nature in relatively small quantities. Synthetic forms of the naturally occurring minerals, as well as many species having no known natural counterpart, have been prepared by a hydrothermal process. An important characteristic of the zeolites is their ability to undergo dehydration with little or no change in crystal structure. The dehydrated crystals are honeycombed with regularly spaced cavities interlaced by channels of molecular dimensions which offer a very high surface area for the adsorption of foreign molecules.