Though most known examples are small, this slag is remarkable for its size and the spectrum of colors preserved on its iridescent surface. While it is typically understood that slag is waste from the process of glassmaking, recent studies have suggested that slag was traded in antiquity, as the raw materials required for making glass were limited to a comparatively small geographic range (see S. Payner and C. Jackson, “Re-used Roman Rubbish: A Thousand Years of Recycling Glass,” Post-Classical Archaeologies 6, 2016, pp. 31-52). The slag would be melted locally and then fashioned into vessels or beads. For a related example, no. 51.1.87 in the Corning Museum of Glass.