Italian zeolitized rocks of technological interest

Abstract

Abstract. Large areas of Italian territory are covered by thick and widespread deposits of zeolite-bearing volcaniclastic products. The main zeolites are phillipsite and chabazite spread over the whole peninsula, and clinoptilolite recorded only in Sardinia. A trachytic to phonolitic glassy precursor accounts for the formation of the former zeolites characterized by low Si/A1 ratios (~< 3.00), while clinoptilolite is related to more acidic volcanism. The genesis of most of these zeolitized deposits is linked to pyroclastic flow emplacement mechanisms characterized by quite high temperatures and by the presence of abundant fluids. The main utilization of these materials has been and still is as dimension stones in the building industry. Currently, limited amounts are also employed in animal farming (dietary supplement, pet litter and manure deodorizer) and in agriculture as soil improvement and slow-release fertilizers. New fields of application have been proposed for these products on account of their easy availability, very low cost, their high-grade zeolites (50 70%), and good technological features such as high cation exchange capacities and adsorption properties. minerogenetic processes leading to their formation have received substantial stimulus. In particular, studies have focused on the products of Quaternary volcanism in central-southern Italy, although researches highlighting the presence of zeolitized materials within the Apennine sedimentary successions and Sardinian pyroclastites have also been completed.The extremely complex question of zeolitization has been tackled, taking into account both mineralogical and all the geological, volcanological, petrographical and geomagnetic information required to draw up valid genetic models. Valuable contributions to our knowledge of zeolitization processes have also been provided by laboratory simulations, which followed the evolution of the chemical and mineralogical composition of fluids and solid phases respectively, in the course of the interaction between volcanic glass and solutions.The present study updates knowledge on Italian zeolitized volcaniclastic rocks and the perspectives for their exploitation in technological fields.

Humic acid sorption properties of calcium-rich derivatives of Neapolitan Yellow Tuff

“…This is the most recent (12,000 years ago) zeolitized formation of the Phlegraean Fields (Naples, Italy), which covers an area of about 13 km 2 [12]. The typical composition and the physical-chemical properties of this rock have been reported previously [11].…”

Frontal polymerization as a convenient technique for the consolidation of tuff

“…A substantial portion of this volcaniclastite (> 50 vol.-%) was involved in diffuse zeolitization processes that determined the crystallization of phillipsite and, subordinately, chabazite and analcime. The main content of these authigenic phases generally exceeds 50 wt.-% and sometimes can reach 70±80 wt.-% [34][35][36][37]. It owes its fame to the lithified facies that have been used as a building material since ancient times because of its color, light weight, and good insulating properties; at the same time, it is weak enough to be easily sewn into dimension stones.…”

Hydrothermal Conversion of Trachytic Glass to Zeolite. 3. Monocationic Model Glasses

“…This is evidence of the decisive role played by the glass composition on the phases formed and on the typical phillipsite-chabazite-analcime assemblages usually found in trachytic volcaniclastic deposits, such as in Italy, Germany, and Canary Islands (de' Gennaro et al, 1995;de' Gennaro and Langella, 1996). In fact, the above phases are the only zeolites formed in nature by the transformation of glasses with a Si/A1 ratio ranging between 2.33-2.88 (de' Gennaro et al, 1987a;1987b).…”

“…(1994). Scanning electron microscope (SEM) observations showed that phillipsite crystallization often preceded chabazite, although a later formation of phillipsite could not be excluded in some cases (Scherillo and Scherillo, 1990;de' Gennaro and Langella, 1996). The present study examines more closely the role of cations, either in the precursor glass or in the contact solution, in the transformation of trachytic glass into phase assemblages characteristic of Neapolitan yellow tuff and other Italian tufts (phillipsite, chabazite, and/or analcime).…”

“…The zeolitization of this glassy precursor by the action of fluids, in a genetic environment linked to the eruptive mechanism (de' Gennaro et al, 1995), gave rise to phillipsite, subordinate chabazite and, in some cases, analcime (de' Gennaro et al, 1982a(de' Gennaro et al, , 1987a. The former two zeolites show a very similar chemical composition, except for small differences in exchangeable cations (de' Gennaro and Langella, 1996).…”