Mosaic Tesserae from the Roman Villa of Aiano in Tuscany (Italy): Characterization via a Non-Invasive Protocol

Highlights: Glass tesserae from the archeological site of Aiano have never been studied in depth. The composition of the glass is important to understand the area and period of production. Non-invasive investigations provided a first characterization of the tesserae in terms of coloring agents and opacifiers and allowed the identification of recycled glass. The use of a well-established non-invasive diagnostic protocol was a winning tool for a first classification of the glass. The mosaic tesserae that are the topic of this study were found during an archeological excavation in a Roman villa at Aiano, in the municipality of San Gimignano, Tuscany (Italy). Many thousands of tesserae were found in the site in many different stratigraphic units (US). For this study, 392 tesserae mainly from three US (US 1095, US 5010 and US 5015 being the most consistent ones) were selected for non-invasive analyses. They might be tesserae coming from different places, collected to be reused or melted down to create new glass objects. The characterization of the tesserae, divided in various groups depending on their color, is an important tool in evaluating their compositional homogeneity/inhomogeneity. The presence of certain markers, such as the opacifiers based on Sb or Sn, could be helpful also in approximately dating the tesserae, since, as reported in the literature, various opacifiers were used in different periods. A well-established diagnostic protocol, based only on non-invasive techniques, allowed us to study a large number of tesserae, which certainly did not derive from a single mosaic and could have been of very different ages, compositions and origins. This procedure has proven to be a winning tool for this aim.