Analcime and Natrolite of South Shahr-e-Rey, North Central Iran

The minerals identified in the Sahr-e-Rey region, in order of their relative time of formations, are primary calcite, tetranatrolite, analcime, natrolite, mesolite, stilbite, secondary calcite and quartz. The formation of zeolites begins with a sodium zeolite of low Si/Al ratio content. They continue to form with gradual increase of calcium and Si/Al ratio contents and terminate with secondary calcite or sometimes with silica. There has been found some similarities between the sequence of formation of zeolites in amygdales and veins of Shahr-e-Rey and Kuh-e-Aradeh. The analcime formula of the study region, Na15.6Al15.2Si32.7O9610.6 H2O, shows that it has a hydrothermal origin