Thirty-two glass objects (third to ninth centuries ad) have been investigated by means of SEM-EDS, EMPA, ICP-MS and LA-ICP-MS. Siliceous sands and natron were identified as the vitrifying and the fluxing agents, respectively. Colouring agents were iron for yellow/-green, aqua blue and blackish glass; cobalt for blue and, combined with iron, for brownish glass; and copper and lead antimonates for one emerald green glass. Antimony was the main decolourizer, while manganese was rarely used or effective. Half of the collection was probably of Levantine origin, while the other half was assigned to the North African coast (Egypt?). The reliability of the CaO-rich HIMT glass group has been consolidated. [ABSTRACT FROM AUTHOR]