Experimental studies on zeolite formation conditions

Natural zeolite formation was simulated in experiments using both natural basaltic and rhyolitic glass, nepheline and oligoclase as starting materials; the reacting solutions were Na, K-, Ca- solutions of different concentrations. Gismondine and thomsonite were synthesized from nepheline only; faujasite-type zeolite X, levyne and scolecite from basaltic glass only; clinoptilolite, epistilbite and mordenite from rhyolitic glass only; garronite from both oligoclase and basaltic glass, heulandite from both oligoclase and rhyolitic glass; merlinoite from both basaltic and rhyolitic glass, phillipsite from nepheline, basaltic and rhyolitic glass; analcite and wairakite from all the starting materials investigated. Solution pH primarily controls zeolite Si/Al ratio, although the influence of starting material Si/Al ratio is affected profoundly by Si removal or addition (through the migrating solution). The concentration and distribution of alkali and alkaline earth cations in the zeolite being formed are determined by their amounts and concentrations both in the starting material and in the initial solution. Zeolite water content is affected by T as well as reaction time. In closed- system reactions starting material, pH, T and reaction time are factors of equal significance.