Zeolites

Abstract

Zeolites are typically hydrated aluminosilicate minerals with a complex cation chemistry that is usually dominated by alkalis and alkaline earth metals. They are formed by low-temperature (generally less than 200°C) alteration of volcanic and other feldspathic rocks and are often associated with various clay minerals. They occur in igneous, metamorphic, sedimentary and hydrothermal environments, mostly from the passage of aqueous fluids during diagenesis and very low-grade metamorphism (and thus defining a facies of metamorphism). Their presence and distribution are good indicators of hydrothermal alteration environments and their distribution can be used to determine palaeogeothermometric regimes. Their crystallographic structure and chemical composition impart numerous useful properties (particularly in ion exchange or as “molecular sieves”) which make them valuable in industry. Because of this, many hundreds of synthetic zeolites and “zeotypes” (materials with similar structures) are now manufactured and used for a variety of specific industrial applications.