The palaeo-Christian glass mosaic of St. Prosdocimus (Padova, Italy): archaeometric characterisation of tesserae with antimony- or phosphorus-based opacifiers

► Multi-methodological approach on 55 palaeo-Christian opaque and coloured tesserae. ► Identification of production technologies of glass tesserae. ► Subdivision into two main groups having different glassy matrixes and opacifiers. ► The same “glass base compositions” were used for transparent and opaque tesserae. ► The opacifiers identified, and not the colourants, support technological transition.