Azione delle crescita dei licheni sulla pietra nell'area archeologica di Fiesole

Abstract

The archaeological area in Fiesole, where a local sandstone (Pietra Serena) was mainly used, was taken into consideration with the purpose of investigating the mechanical and chemical alteration possibly due to lichen growth. The taxonomic data allowed identification of almost 40 species. Distribution data allowed definition and localization of the most frequent species, therefore permitting a choice of those to be taken into consideration in relation to their effect on the stone. Observation of stone specimens under optical and scanning electron microscopes showed the morphology of mechanical alterations caused by the growth of some lichen species. The map of distribution of calcium determined by analysis carried out under SEM equipped with an energy dispersive X-ray spectrometer (EDS) showed that some species cause modification of the mineralogical stone composition. Moreover, analyses by X-ray diffractometry, in connection with the above results, allow the identification of the production of calcium oxalate due to tlhe growth of some species.