Natural zeolites exhibit three distinct types of solid solutions, including framework substitution of Si for Al, extraframework substitution between cations, and vacancy-based solutions between fully hydrated and zeolites and their dehydrates.  The extent and compositions of natural and experimentally-modified zeolites will be reviewed to elucidate the extent of these solutions and coupling between them.  Recent theoretical and experimental progress now permits quantification and modeling of the thermodynamic consequences of these solutions.  One unanswered question in zeolite science is why the compositional ranges observed in nature for many zeolites are considerably more limited than observed experimentally.  Thermodynamic calculations of the compositions of common rock-forming zeolites coexisting with other minerals and aqueous solutions reveal that in addition to crystal-chemical limits on zeolite composition, the compositions of these minerals in natural systems are often limited by the stability of other phases.

Zeolite solid solutions: Crystal chemistry, solution thermodynamics, and controls on the compositions of zeolites in natural systems

239th National Meeting (2010)

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