Blue shadows of Roman glass artefacts

Glass is one of the ancient human products most often traded for long distances from the place of raw material supply. Provenance studies on this kind of artefact are mainly based on the comparison of major and trace elements among archaeological samples. The paper proposes a step-by-step geochemical organized protocol that considers the elements with prominent influence on glass composition, helping in a fine discrimination of compositional groups and, consequently, an easier identification of provenance in archaeological artefacts. The proposed approach is presented through the case study of Roman blue glass samples, dated from the 1st century to Late Antiquity and coming from the Palatine Northeast archaeological site. Optical Microscopy, SEM-EDS, EMPA and LA-ICP-MS results are discussed to gather information on network former, flux, colourants and decolourants. In addition, the comparison with literature provides additional information on chemical groups of ancient glass spanning from the 1st to the 5th century.