Villa del Casale (Piazza Armerina, Sicily) : stone and glass tesserae in the baths floor mosaics

The Villa del Casale at Piazza Armerina (Sicily) is world famous for its beautiful and extensive mosaic floors dating to the fourth-century A.D. Before a recent restoration of the Villa, it was possible to take a representative sampling of coloured glass and stone tesserae from the baths’ floors that were examined by chemical and minero-petrographic analysis, respectively, with the goal of determining the production-centre/s of the glass, and the provenance of the stones. The laboratory techniques used were SEM-EDS on polished sections, powder XRD and polarised OM on thin sections, extended to reference stones found in a Villa’s ancient storehouse. The obtained results had shown that the white and pinkish tesserae were exclusively made of local (from the Caltanissetta province) limestones, while the black ones were cut from an obsidian, likely of a Liparote origin; the turquoise and gold-leaf tesserae were exclusively made of glass manufactured according to the Roman and Byzantine tradition while both stone and glass were used for the dark and yellow hues (giallo antico was identified among stone yellow hues). As for the glass tesserae, the results of the chemical analysis of a few samples (mostly erratic) have allowed to date them to the fifth- to sixth-century and to the eighth- to ninth-century A.D. and thus to testify to a hitherto unknown ancient restoration of the Villa mosaics