A term now used to designate any one of a family of minerals, hydrous silicates of alumina, with lime, soda, potash, or rarely baryta. Here are included natrolite, stilbite, analcime, chabazite, thomsonite, heulandite, and others. These species occur of secondary origin in the cavities of amygdaloid, basalt, and lava, also, less frequently, in granite and gneiss. So called because many of these species intumesce before the blowpipe.
(1) (Geology) Any of various hydrous silicates that are analogous in composition to the feldspars, occur as secondary minerals in cavities of lavas, and can act as an ion-exchanger. (2) (Chemistry) Also, any of various natural or synthesized silicates of similar structure used especially in water softening and as an adsorbent and catalyst. (3) (Water Quality) A type of ion exchange material used to soften water. Natural zeolites are siliceous compounds which remove calcium and magnesium from hard water and replace them with sodium. Synthetic or organic zeolites are ion exchange materials which remove calcium or magnesium and replace them with either sodium or hydrogen.