Building Stones and Technological Materials of the Campi Flegrei Caldera, Italy

This chapter highlights how, lacking high value rocks in the Campanian area (South Italy), those produced by the activity of the Campi Flegrei volcanic field, have represented a fundamental resource that has made possible to carry out important architectural works. These works can be admired in the numerous archaeological sites, hamlets and most notably throughout the city of Naples, whose Ancient Centre is a splendid example of a stratified city. Phlegraean Tuffs (i.e., Neapolitan Yellow Tuff, various facies of the Campanian Ignimbrite) and Lavas are the “stones” that mostly have marked the architectural history of the city. In some cases, thanks to the mastery of the lapicidi (Italian for stone craftsmen), these stones have been worked to obtain works of art of priceless value. The use of imported stones (marbles, granites, etc.) solely for particular architectural elements (i.e., church and building portals, columns) further corroborates the aforementioned. When the Phlegraean rocks were used for purely structural functions, they were covered with plaster made with Phlegraean sands and aggregates, or, less frequently, with stone slabs from other exploitation sites in the Campania region. However, these rocks have had an important role not only in the building industry. As demonstrated by numerous researches carried out in over sixty years, the Neapolitan Yellow Tuff and the yellow facies of the Campanian Ignimbrite with a high content of zeolites (phillipsite and chabazite), can be used, exploiting the peculiar properties of these minerals, in numerous technological sectors, in particular in those with environmental implications.