Mineralogical and petrographic analysis of early-Hellenistic mortars from a Punic-Roman residential area discovered at Palermo (Sicily)

Lime based mortars dated back to 4th-3rd century BC were sampled in a Punic-Roman residential area recently brought to light in the historical centre of Palermo. The collected mortars have been analyzed by optical microscopy (PLM), X-ray powder diffraction analysis (XRPD) and scanning electron microscopy coupled with energy dispersive spectrometry (SEM-EDS). The study was aimed to characterize these materials from the textural and compositional point of view in order to define the recipes. The mineralogical and petrographic investigations allowed to establish 4 different recipes used for the formulation of the studied floor and wall mortars in terms of both compositional and textural features. The aggregate resulted to be composed by different proportions of alluvial calcareous and siliceous sand or else by “cocciopesto”. Aerial lime based mortars (for the most part magnesium-bearing) have been used for wall coatings and decorations, while the use of hydraulic lime based mortars was mainly documented for floor covering. Furthermore, it is interesting to report an unusual mosaic floor covering manufactured with “tesserae” obtained from over fired limestone scraps (locally produced) and aerial lime-based binder. These results contribute to improve the knowledge concerning raw materials and recipes (relative to the end-use) employed for mortar manufacturing at Palermo in antiquity. A diachronic correlation with previously studied mortars manufactured in Baroque and Neoclassic periods was also made. It allowed to demonstrate a surprising continuity both in the selection criteria of the raw materials and in the formulation of the specific recipes. Moreover, through the study of the ancient recipes it will be possible to formulate restoration mortars with full awareness.