Mineralogical and technical features of zeolite deposits from northern latium volcanic districts

Six pyroclastic formations from volcanic districts of northern Latium have been investigated. These formations were subjected to post-depositional diagenetic processes which gave rise to the crystal lization of chabazite and subordinate phillipsite. Zeolite grades are greater than 50 wt% for most of the analysed samples. Generally, the phillipsite content does not exceed 20 wt%. The chemical composition of chabazite is quite variable as far as the different formations are considered, but Ca and K generally prevail over the other extra frame work cations . A very high Ca content is responsible for incomplete cation exchange process, both due to the preferential selectivity of the zeolite towards cations of higher valence and to the steric hindrance of the «ingoing» cation. The cation exchange capacity of the bulk rock is not influenced by the joint presence of the two zeolites. The large available tonnages of these materials and the well known selectivity of chabazite towards many polluting cations offer good potential for applications in several technological fields.