Roman glass across the Empire: an elemental and isotopic characterization
This study focuses on natron glass, dated from the 1st to 5th century AD, excavated in different areas of the Roman Empire. The eastern side of the Roman Empire is accounted for by three archaeological sites, Petra and Barsinia, both in Jordan, and Gonio, in Georgia. The Italian peninsula is represented by the Iulia Felix and Embiez shipwrecks, and by samples from Augusta Praetoria. Samples from Barcino in Spain are examples of the western side of the Empire, and the sites of Tienen and Oudenburg represent the northern provinces. No clear distinctions in glass composition and origin between the different regions of the Roman Empire can be made based on the major elemental compositions. However, the western, central and eastern Roman Empire samples can be divided into two groups, coloured and colourless, which also are reflected in the K2O contents. Sr–Nd isotopes, used for provenancing geological raw materials in primary glass production, indicate an eastern Mediterranean origin (εNd between −2.5 and −6.0) for most of the samples. Conversely, samples with more negative εNd, between −7.02 and −10.8, indicate a western Mediterranean origin. By applying this technique on samples from well known archaeological contexts, this study demonstrates that several primary glass factories were located throughout the Roman Empire. This is in contrast with current interpretations of late Roman to early Byzantine data.