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About Zeolites

About Zeolites

Q. What is a zeolite?

A. Natural zeolites are naturally occuring porous minerals with over 40 different varieties. Zeolites are mined from large ore deposits that were formed when volcanic ash reacted with salt water. Some applications of zeolites are odor absorbers (found in kitty litter), food additives, and waste water filtration systems. The background of this page is zeolite powder magnified 20 times.

The above picture shows part of the St. Cloud Mining Company's zeolite mine in Winston, New Mexico. Photo courtesy of Patrick Freeman, President of St. Cloud Mining Company

Synthetic zeolites are manufactured by artificially heating similar raw materials that are found in natural zeolites. Synthetic zeolites have a smaller silicon-to-aluminum ratio and are less resistant to acid than natural zeolites.

The subcommitte on zeolites of the International Mineralogical Association, Commission on New Minerals and Mineral Names, proposed this definition of a zeolite in 1998:

A zeolite mineral is a crystalline substance with a structure characterized by a framework of linked tetrahedra, each consisting of four O atoms surrounding a cation. This framework contains open cavities in the form of channels and cages. These are usually occupied by H20 molecules and extra-framework cations that are commonly exchangeable. The channels are large enough to allow passage of guest species. In the hydrated phases, dehydration occurs at temperatures mostly below 400 degrees C and is largely reversible. The framework may be interrupted by (OH,F) groups; these occupy a tetrahedron apex that is not shared with adjacent tetrahedra. [Armbruster et al., 2001]

For More Information

International Zeolite Association
This organization was formed in 1973. They "promote and encourage the development of all aspects of zeolite science and technology." They organize conferences and other activities, and their web site has links to publications and databases.

ZEO Agronomic Technology
This site has lots of information about zeolites, what they are, and their applications.

Synthetic Zeolite Manufacturing
This web page is from Japan's National Institute of Materials and Chemical Research's web site. The page describes the process of making a synthetic zeolite.