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Zeolites, The Sharing Minerals

( EXCERPTS FROM A LONGER ARTICLE)

Zeolites are hydrated silicates of aluminum, calcium, sodium and potassium. They provide fine specimens for the collector. The word zeolite means “boil stone”, referring to the water expelled when zeolites are heated. The approximately 50 minerals of this group have unique physiochemical properties. When heated,, the water of hydration is lost gradually and continuously, rather than at a certain temperature. They also easily exchange their original alkali ions for other minerals. These two things make them very useful in the home and in industry.

Zeolites have alumino-silicate framework structures containing channels filled with water and exchangeable ions. The ratio of aluminum and silicon to oxygen is always one to two. The ion exchange at low temperature is the basis of the water softening process. When dehydrated, zeolites may absorb not just water, but vapors, gases and fluids. At 250 degrees C. water is lost and can be reabsorbed at room temperature. Therefore, zeolites are excellent desiccants. Synthetic zeolites are the compositions used extensively..... in water softening and purification. Natural zeolites could do the job if a low cost source was to be had Permutit is the synthetic used in water softening and the sugar industry.

Zeolites have a low specific gravity and are soft with a range of 3.5 to 5.5 Good crystals are common., usually colorless and translucent. They occur in cracks, vugs, and crevices in basic igneous rocks such as basalt, and are also found in granite and mica schist. (I read the much more technical article because I have always wondered just what kind of a thing a zeolite was. Now I have a better idea.)

Author Lloyd L. Brown. Via Breccia Dec. 0/6-Jan.07 (Santa Clara CA) and several sources over a 6 year period.