Dating the mosaics of the Durres amphitheatre through interdisciplinary analysis

This article presents the results of an interdisciplinary investigation of the mosaics in the main chapel of the Durres amphitheatre, the interpretation and chronological attribution of which have been the subject of debate. Art historical considerations about the mosaic's cultural and artistic affiliations are combined with in situ assessments of the mosaic techniques and physico-chemical analyses of 111 glass tesserae by means of scanning electron microscopy with an energy-dispersive detector (SEM-EDS) and laser ablation inductively coupled mass spectrometry (LA-ICP-MS). Our results show that the raw glass used for the mosaic tesserae derives from two primary production centres but with evidence of substantial recycling: Foy-2, possibly of Egyptian origin, and Levantine I from the Syro-Palestinian coast. While lead stannate, copper and manganese are colorants found commonly in tesserae from different Mediterranean contexts, cobalt correlated with nickel and lead-tin associated with arsenic and antimony have been attested in mosaic tesserae here for the first time. The chronological range of the raw glasses and colorants provides strong evidence for a sixth- to eight-century CE date for the tesserae. The stylistic and iconographic parallels of contemporary mosaic decorations and the mosaic techniques reflected in the plaster layers, preparatory paint and particular setting of tesserae corroborate this timeframe. In terms of the material provenance and artistic features, the mosaics of the Durres amphitheatre clearly reflect the merging of eastern and western elements, typical of the early medieval Adriatic, while visual references to Byzantine imperial iconography may have served to reassert a link with Constantinople and the Byzantine court. Taken together, the material, technical and artistic data reveal the cultural and economic connectivity that shaped the art of mosaic making in the late antique and early medieval period.