Zeolites The Zeolite Group Natural & Synthetic Minerals Uses

Zeolites

Zeolites are a group of microporous aluminosilicate minerals that are related in structure, habits, and occurrence. They are usually found in zeolite deposits which are of igneous origin. They are hydrous aluminum silicates that contain sodium or calcium, which can replace one another. Natural zeolites form where volcanic rocks and ash layers react with alkaline groundwater. They also crystallize in shallow marine basins over periods of thousands to millions of years. They typically form in the cavities of volcanic rocks, and are the result of very low grade metamorphism. With some zeolites only very small amounts of heat and pressure are needed for this process to occur, yet with others a great deal more is necessary. Naturally occurring zeolites are rarely pure. They are contaminated to varying degrees by other minerals, metals, quartz, and even other zeolites. The zeolite group is in the tectosilicates subdivision of the silicates group.

Naturally occuring zeolites are mined in many areas of the world, most commonly in Eastern Europe, Western Europe, Australia, and Asia. North America is also a source of zeolites, but only to a very small degree in comparison to the other locales. Zeolites are easily synthesized in the laboratory. They have even been grown on board the space shuttle. Both natural and synthetic zeolites are widely used commercially due to their unique adsorption, ion exchange, molecular sieve, and catalytic properties. The water within their structures is in microscopic channels and can be removed without altering the structure by heating the mineral. Some commercial uses for zeolites are: medical purposes, the petrochemical industry, the nuclear industry, agriculture, animal welfare, heating and refrigeration, detergents, construction, aquarium keeping, space hardware testing, cat litter, and many more uses. Zeolite specimens are also popular with mineral collectors because of their aesthetic properties. Many of the different varieties of zeolites are quite beautiful, especially when seen in clusters.

There is a member of the zeolite group which is quite popular and is occasionally seen in the jewelry industry, even though it is

considered to be rare. Thomsonite forms beautiful nodules which can be polished. When polished some may exhibit a cat's eye, or chatoyancy. They display concentric rings in combinations of colors. The most commonly seen colors are shades of black, white, orange, red, pink, and green. Some of these nodules have inclusions of copper which may be referred to as "copper eyes," or orbs. These stones are collected along the shores of Lake Superior in Minnesota and Michigan. The nodules eroded from basalt lava flows. Scuba divers can also be found scouring the bottom of the lake in search of these pretty nodules.

There are several minerals which are often found with, or are associated with zeolites, but they are only "relatives." They may have similar cage-like framework structures or have other similar properties, but they are not zeolites. Some of these minerals are: Andradite, Apophyllite, Cavansite, Epidote, Gyrolite, Hsianghuaite, Kehoeite, Lovdarite, Maricopaite, Okenite, Pahasapaite, Partheite, Prehnite, Roggianite, Tacharanite, Tiptopite, Tobermorite, and Viseite. Some may even refer to some of these minerals as zeolites, but again, they are not zeolites.

The Zeolite Group Members

Amicite, Analcime, Barrerite, Bellbergite, Bikitaite, Boggsite, Brewsterite, Chabazite, Clinoptilolite, Cowlesite,

Epistilbite, Erionite, Faujasite, Ferrierite, Garronite, Gismondine, Gmelinite, Gobbinsite,

Gonnardite, Goosecreekite, Harmotome, Heulandite, Laumontite, Levyne, Mazzite, Merlinoite,

Mesolite, Montesommaite, Mordenite, Natrolite, Offretite, Paranatrolite, Paulingite,

Pollucite, Scolecite, Sodium Dachiardite, Stellerite, Stilbite, Tetranatrolite, Thomsonite, Tschernichite,

Wairakite, Willhendersonite, and Yugawaralite.

*Pictured at the top of the page is a cluster of beautiful Pearlescent Pink Heulandite crystals on matrix from India.

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