Excavations at the Roman villa of Noheda (Spain) revealed the remains of an exceptionally elaborate fourth-century floor mosaic that contains a surprisingly large number of glass tesserae, representing a broad spectrum of colors. This paper presents the results of the chemical (LA-ICP-MS) and microstructural analyses (SEM-EDS, XRPD) of 420 glass tesserae from these mosaics. The high number of data allowed us to establish the compositional variability and to elucidate questions of supply in relation to a large-scale artistic campaign. The tesserae from Noheda were almost exclusively made from recycled mixed Roman Mn and Sb base glass, thus demonstrating that recycling of Roman base glasses was common practice in the fourth century, occurring on a near industrial scale. It also suggests that the workshops specializing in the production of mosaic tesserae might have been in the western Mediterranean. A limited number of coloring and opacifying additives (Mn, Co, Cu, Sb, Pb) were identified, which resulted in a wide range of hues. These were differentially associated with various trace elements, which implies the use of different raw materials. A sub-set of red, green, and orange tesserae reflect distinct base glass characteristics as well as coloring technologies that point to an Egyptian provenance.
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