Zeolite Deposit of the Aftar Region, West Semnan, Central Alborz, Iran

Larger deposits of potential economic interest are at: 1) Aftar, at 40 km west Semnan, 2) Sartakht at 20 km south-east Semnan and 3) Melheh at 30 km south-east Semnan. All three deposits are of Eocene age and rich in clinoptilolite. The sedimentary zeolites, clinoptilolite, mordenite and heulandite occur in Aftar region as diagenetic products of rhyolitic to dacitic tuff rocks of the Semnan Formation at the north of Aftar village. Different diagenetic silicate minerals occur in upper, middle and lower parts of Semnan Formation. Smectite, mordenite, clinoptilolite, quartz, opal-CT and feldspar in the upper part, clinoptilolite, mordenite, with minor amounts of opal-CT and quartz in the middle part, and heulandite as the major component of the lower part.