Occurrence, Diagenesis and Crystal Structure of Zeolites

From about 80 known types of natural zeolites, at least 20 have been reported from repositories in zeolitically altered rocks. However, only the following nine (analcim, chabazite, clinoptilolite, erionite, ferrierite, heulandite, laumontite, mordenite and phillipsite) are known to occur in repositories large enough to mine. These zeolites, which were formed by the natural alteration of volcanic aluminosilicate ash, occur in either closed system or open system deposits. Clinoptilolite is by far the most common zeolite. These minerals occur in rocks and sediments, seemingly formed in widely disparate environments, which include deep sea sediments, continental accumulations in thick basin fills or in shallow lakes, and also in some lava flow sections. Currently, over thousand occurrences of zeolite minerals have been reported, predominantly from sedimentary rocks of volcanic origin in more than 50 countries of the world. The ready availability of zeolite-rich rocks at low cost and the shortage of competing minerals are probably the most important factors for its large-scale use. In this chapter crystal structure of sodalite, LTA, faujasite, erionite and clinoptilolite is described, in conclusion focussing on the Slovakian clinoptilolite-rich tuff, respectively.

Keywords: Clinoptilolite, crystal structure of zeolites, deep marine sediment, diagenesis, erionite, faujasite, geothermal system, hydrologically closed and open systems, LTA, occurrence, Slovakian clinoptilolite-rich tuff, sodalite.