New geochemical and isotopic insights into the Late Antique Apulian glass and the HIMT1 and HIMT2 glass productions—the glass vessels from San Giusto (Foggia, Italy) and the diagrams for provenance studies

The research focused on a collection of 37 Late Antique glass fragments, found at the archaeological site of San Giusto (southern Italy). The analyses performed by SEM- EDS, EMPA and LA-ICP-MS showed that all samples are constituted by natron-based soda-lime silica glass and allowed clarifying the distinction between Egyptian HIMT1 and HIMT2 productions. The comparison with the composition of the available glass reference groups was verified through three ternary diagrams (provided here for the first time). The results grouped San Giusto samples into HIMT1 (7 samples), HIMT2 (8 samples) and Levantine (13, plus maybe other 3 samples) productions. A convincing provenance assignment was not feasible for six samples only. The isotopic analyses (87Sr/86Sr and 143Nd/144Nd), performed on a selected set of ten samples, provided further information both in terms of glass technology and provenance, as well as in terms of reference groups characterisation. Particularly, the results demonstrated that nine out of a total of ten samples were made using a limestone-bearing sand enriched with variable amount of marine shells and provided further evidence for the distinction of the HIMT1 and HIMT2 groups; the latter overlapping the Levantine field in the 87Sr/86Sr versus εNd binary diagram. From a technological point of view, the importance of separating the likely ‘fresh’ materials from those intentionally recycled or coloured was put into clear evidence, especially in relation to provenance assignments. Lastly, an interesting technological feature has been observed in sample no. 9, where the composition of the main body of the vessel turned out to be different from that of the handle. This result provided clear evidence of the fact that different glass batches could have been used for the different parts of a single vessel body.