- any of a group of hydrated silicates of aluminum with alkali metals, commonly occurring as secondary minerals in cavities in basic volcanic rocks: used for their molecular sieve properties because they undergo dehydration with little or no change in crystal structure.
- any of a large group of glassy secondary minerals consisting of hydrated aluminium silicates of calcium, sodium, or potassium: formed in cavities in lava flows and plutonic rocks
- any of a class of similar synthetic materials used in ion exchange and as selective absorbents
