Stone materials used in the masonry of Ortigia (Siracusa, Sicily)

Abstract

This chapter describes the study of the natural stones used as constructional materials in the buildings of Ortigia. Identification and classification of lithotypes used and knowledge of their places of origin; macroscopic survey of their state of conservation; and determination of porosity characteristics and possible presence of soluble salts, in relation to their state of conservation are also described. The samples of surface materials in a variety of states of conservation were taken from different types of buildings, in different parts of the area under study. As a means of establishing provenance, samples of living rock were taken from the outcrops and quarries, extant or in disuse, in various parts of the province. The studies that were carried out on the collected samples were mineralogical and petrographic analysis by observation of thin sections and by X-ray diffraction (XRD) analysis; quantitative analysis by atomic absorption spectrophotometry; porosimetric analysis; and measurement of soluble salts content by ions chromatography. The stones recognized were classified as: fine and coarse Palazzolo stone (Pf and Pc groups); fine and compact oolitic calcarenites (Op and Oc groups); and fine packstone-wackestones, Cc group. The importance of the study carried out on the constituent stones of Ortigia lies in the documentation of the historically used building materials and with regard to the choices concerning future conservation works. It is necessary to bear these intrinsic characteristics of the materials for selection of methods and products to be used in their conservation or their replacement.