Zeolites are minerals that have a micro-porous structure. "stone that boils," They are basically hydrated alumino-silicate minerals with an "open" structure that can accommodate a wide variety of cations, such as Na+, K+, Ca2+, Mg2+ and others. Natural zeolites form where volcanic rocks and ash layers react with alkaline groundwater. Zeolites are the aluminosilicate members of the family of microporous solids known as "molecular sieves". The term molecular sieve refers to a particular property of these materials, i.e. the ability to ively sort molecules based primarily on a size exclusion process. This is due to a very regular pore structure of molecular dimensions. The maximum size of the molecular or ionic species that can enter the pores of a zeolite is controlled by the diameters of the tunnels. These are conventionally defined by the ring size of the aperture, where, for example, the term "8ring" refers to a closed loop that is built 8 tetrahedrally coordinated silicon (or aluminium) atoms and 8 oxygen atoms. Applications: Zeolites are widely used in Nuclear Industry, Agriculture, Animal Welfare, Medical, Heating and refrigeration, Detergents, Construction, Aquarium keeping.