Roman and late-Roman glass from north-eastern Italy: The isotopic perspective to provenance its raw materials

The majority of glass analysed, independent from age, shows values of strontium isotope ratios close to that of modern seawater, indicating that the source of lime in the glass was marine shell, and likely coastal sands were used in its production. The Nd signature of all late-Roman glasses from Aquileia and of the majority of the Roman ones from Adria, independent from their chemical composition, is homogeneous and higher than −6 εNd, supporting the hypothesis of an eastern Mediterranean origin, probably located on Syro-Palestinian coast. However, the composition of late-Roman samples with HIMT signature, with lower 87Sr/86Sr values correlated to higher contents in Fe2O3, TiO2, MgO and lower contents in CaO, suggests an area of origin for this glass on the Egyptian coast. In addition, the different Nd signatures of two Adria Roman glasses (εNd < −7) suggest their primary production in western Mediterranean. Oxygen isotopes proved to be a further diagnostic method to discriminate natron and soda plant ash glass, and different silica sources, in the case of the soda plant ash glass. The combination of isotopic and chemical data supports the hypothesis of an eastern Mediterranean origin for late-Roman glass, which may be produced in few primary workshops on the Syro-Palestinian and Egyptian coast, although not necessarily in the same ateliers as have been identified so far. In the case of the Roman glass investigated, although the majority of data suggests an eastern Mediterranean origin, on the basis of Nd isotopes and chemical compositions, the existence of other primary glass producers located in the western Mediterranean can be suggested.