a hard, light-colored, orthorhombic zeolite, NaAlSiO·2HO, characterized by crystals that radiate out, often needlelike, from a central point; hydrous sodium aluminum silicate
See natrolite in American Heritage Dictionary 4
(nāˈtrə-lītˌ)
noun
A mineral in the zeolite family with composition Na2Al2Si3O10·2H2O.