Evaluation of Numidian quartz sandstones from Southern Italy for industrial applications

Abstract

Numidian quartz-rich sandstones collected from four different reconstructed sections along the Apennine chain of Southern Italy, have been studied for their textural, petrographic and geochemical characteristics to verify their potential industrial use. Sampling was carried out along a NW-SE transect: Monteverde and Aquilonia sections at NW (Campania Region) and Valsinni and Rotondella ones at SE (Lucania Region). The sandstones from NW successions are subarkoses with subordinate sublitharenites. High compositional maturity is shown by these sandstones containing high SiO2 values (93wt% in average) and lowest amounts of CaO (0.08 wt%), MgO (0.1wt%), Fe2O3 (0.9 wt%) due to the absence of carbonate components (cement and lithics) and scarce presence of clay-ferruginous cement. The sandstones from SE successions show lower contents of SiO2 (87 wt% in average) and relatively higher contents of CaO (up to 7.4 wt%), MgO (up to 1.9 wt%) and Fe2O3 (up to 4.6 wt%) as compared to the previous ones, connected to the presence of calcite and clay-ferruginous cements; these can be classified as Fe-sands with subordinate sublitharenites. The sandstones from NW area show a better potential vocation to be used in the glass industry. However, the coloring elements contents are too high for clear or optical glass production. They are it is suitable as raw material for colored glass, insulating fibres, foundry molds or air Crete. With the aim of assessing the possible improvement of chemical characters, four granulometric fractions (A< 63 μm, B 63-125 μm, C 125-250 μm and D >250μm) were analyzed considering four samples from NW successions. Based on chemical composition, C and D fractions from Aquilonia area, are the most suitable for a coloured glass, while fractions A (<63 μm) and B (63-125 μm) mixed in proportions of 40 % (A) and 60 % (B), appropriately cleaned of clays, heavy minerals and iron hydroxides, could be used as raw material for the paint industry. The obtained results suggest a complete exploitation of this type of sandstones in the manufacturing industry, reducing waste materials and enhancing the economic value of these resources from southern regions of Italy.