Something old, something new: the late antique mosaics from the catacomb of San Gennaro (Naples)

Compositional and artistic evidence points to the existence of regional mosaic schools in Italy and local variations during the late antique period. Comparing the material characteristics of 285 glass tesserae from the catacomb of San Gennaro in Naples to those of contemporary Italian mosaic assemblages, suggests that a mosaic school flourished in Naples during the late antique period. Using a combination of LA-ICP-MS, SEM-EDS and micro-Raman, it is shown that the mosaics dating to the fourth to ninth century CE were to a large extent produced from reused Roman base glasses opacified with calcium antimonate. At the same time, there is evidence of new, late antique glass groups (Levantine I, HIMT, Foy-2 and Foy-3.2) being used occasionally together with calcium antimonate as opacifying agent. This conservation of a Roman tradition sets the Neapolitan mosaics apart from the rest of Italy. While calcium antimonate has been previously reported in post-Roman base glasses only in four samples from Padova, this is the first time that calcium antimonate has been more systematically detected in late antique glass groups. It appears that antimony was still used in Naples during fifth and sixth centuries, possibly in the form of recycled Roman tesserae. In contrast, none of the novel opacifying techniques that have been recognised at northern Italian sites could be identified at Naples. The relatively high incidence of Levantine I glasses finds a counterpart only in contemporary Ravenna, reflecting Naples’ politico-economic significance within late antique Italy.