The glass mosaics tesserae of “Villa del Casale” (Piazza Armerina, Italy): a multi-technique archaeometric study.

A wide selection of glass tesserae from mosaics of the Roman “Villa del Casale” (Piazza Armerina, Enna, Italy) were characterized from a chemical and textural perspective, with the aimof providing archaeometric information about the raw materials and manufacturing techniques utilized at this archaeological site of utmost importance. The studied samples are vitreous colored tesserae, both opaque and transparent. The textures and chemical compositions of the coloring and opacifying agents were determined through a multi-technique approach based on scanning electron microscopy, X-ray diffraction, electron microprobe analyses for major elements, and inductively coupled plasma mass spectrometry for trace elements. On the basis of major element contents, the samples can be classified as natron-based silica–lime glasses. As regards the opacifiers/coloring materials, a substantial use of Pb and Ca antimonates, and metallic copper was observed. A slight enrichment of heavy rare earth elements (REE) relative to light REE, and a number of positive correlations between high field-strength elements suggest that the raw materials used for the production of the Piazza Armerina tesserae included a mature sand, enriched in quartz and heavy mineral phases.