Mineralogical and technical features of zeolite deposits from northern Latium volcanic district

Six pyroclastic formations from volc anic district s of northern Latium have been inves tigated. These formations were subjected to post-depositiona l diagenetic processes which gave rise to the crystallization of chabazite and subordinate philli psite. 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 vari able as far as the different formati ons are considered, but Ca and K generally prevail over the other extrafr amework cation s. A very high Ca content is responsible for incomple te cation exchange process, both due to the prefe rentia l 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. RIASSUNTO. - Sono state studiate sei formazioni piroclastiche, appartenenti a diversi distretti vulcanici del Lazio settentrionale. Tali formazioni sono state zeolitizzate a seguito di processi diagenetici post­ deposizionali che hanno dato luogo alla formazione