Twenty-five glassy samples, including fragments of objects, molten glass and glass drops originating from a Proto-Byzantine glass workshop of the Catania Roman Amphitheatre, were analysed for major, minor and trace elements. Two main groups of natron-based silica–lime glass were identified, as well as one sample of obsidian (from Lipari Island). The majority of the samples (20) are High Iron, Manganese and Titanium (HIMT) glass. Specifically, most of them (18) can be classified as HIMT1, with only two HIMT2 glasses, according to the latest classification proposed in the literature. Three samples belong to the Levantine I type. In regard to the geochemical signatures of HIMT raw materials, the high abundance of HREE relative to LREE and of HFS elements (Zr, Nb, Ta, Ti, Hf, Th), suggests the use of impure sand, particularly enriched in heavy minerals and/or in mafic phases. Furthermore, the noticeably different contents of all the HFSE in the two main sample sub-groups – enriched HIMT and depleted Levantine I – allow us to propose these elements as discriminating factors between the two glass categories, which were present at the same time.