In nature,zeolites are often formed where Volcanic rock of specific chemical composition is Immersed in water so as to leach away some of The components . composition and pore size , of Course , depend upon what kind of rock minerals Are involved . Millions of years ago ,zeolite Deposits formed when volcanoes erupted Enormous amounts of ash-aluminosilicates of Alkaline and alkaline earths. the chemical reaction Of volcanic ash and salt water resulted in the Formation of natural zeolites. Natural zeolite are Also form as a devitrification product (the Conversion of glass to crystalline material) of Volcanic glass in tuffs. Tuffs are consolidated Pyroclastic rocks . the devitrification occurs when The glass is in contact with saline waters . natural Zeolites are also found in the vesicles of volcanic Rocks such as basalts , rhyolites and andesites