Clay minerals and iron oxides-oxyhydroxides as fingerprints of firing effects in a limestone monument

Abstract Different Portuguese limestones-Encarnadao, Amarelo de Negrais, Lioz and Gresoso-have been widely used as building materials and ornamental stones in the architecture of Lisbon (Portugal) area. The aim of the study of those materials was focused on fire-induced stone damage, mainly on identifying the thermal transformations of clay minerals and iron oxides-oxyhydroxides. Taking into account an applied component to the cultural heritage, a special attention was given to one of the most ancient Portuguese monuments — Lisbon Cathedral, specifically its cloister that was severely damaged by a fire that occurred right after the 1755 earthquake. A set of samples collected from outcrops were studied and subjected to artificial heating. The results were compared with those obtained from samples collected in the monument. XRD, SEM-EDS and 57Fe Mossbauer spectroscopy were used. The