Zeolites are the main mineral components in altered volcaniclastic rocks
ranging in age and composition. They form by alteration mainly of volcanic glass in
various geological environments, under variable geochemical and temperature
conditions. Proposed genetic models of zeolite deposits include weathering, diagenesis
in open or closed hydrologic systems, low temperature hydrothermal systems, primary
magmatic environments and impact craters. The most common zeolite species, which
may occur in mineable deposits, are clinoptilolite-heulandite, mordenite, chabazite,
analcime, and phillipsite. Mineable zeolite deposits are widespread in many countries
worldwide. The world annual production of natural zeolites remains essentially constant
over the last 10 years at ca 3 million tons. Although several large high grade zeolite
deposits are currently under operation and numerous studies on the suitability of the
zeolite materials in various applications have been carried out, most of the annual
zeolite production is consumed in massive low value applications like additives in
pozzolanic cement and lightweight aggregates.
Keywords: Formation, deposits, geology, volcaniclastic rocks, geothermal
gradients, metamorphic processes, hydrothermal zeolites, geoautoclaves,
metamorphism, chemical gradients, zonation.
