Decorative stones characterization through spetroscopic methods: mosaic tesserae from an outstanding late Roman villa in Tuscany

In the framework of archeological investigations of an outstanding Roman villa in Tuscany (Villa dell’Oratorio, in the territory of Capraia e Limite, Florence), a characterization of decorative stones employed in mosaic tesserae have been carried out with the aim to identify the raw materials and their supply basin, and to value the ability of the villa owner and builders to obtain supplies at local or possible over local markets. The archaeological and historical context is particularly interesting. The villa, built in the middle of the 4th centuries, probably belonged to the great senator Vettius Agorius Praetextatus, remembered in an inscription found in the site. The importance of this figure in the Late Roman world is underlined by Macrobius, who defined the 4th century as the Saeculum Praetextati, and reflected by the architecture of the building with mosaics: this is a hexagonal structure, of almost 30 meters in diameter, equipped with apsed rooms (at least 5) and similar to some monumental triclinia of Constantinople, dated in the fifth century and related to the Imperial Court. The mosaics unveiled in the villa consist in cubic tesserae made by decorative stones ranging in color from white, to black, from red to yellow and green, along with blue and green glazed elements. To achieve the aim of the study, spectroscopic analysis through X-ray fluorescence (XRF), laser induced breakdown spectroscopy (LIBS) and Raman spectroscopy have been carried out, supported by classical minero-petrographic mehods. The obtained results have been compared with reference data on decorative stones provided in literature for ancient marbles, delineating the commercial movements undertaken the construction of Villa dell’Oratorio and supporting the archeological overview of a such relevant and unique late Roman villa in Italy.