Prior to the eighteenth century, cobalt was exclusively employed as a colouring agent for vitreous materials, and its use appears to be concurrent with the earliest large-scale production of glass during the Late Bronze Age (LBA). LBA cobalt deposits with a distinctive elemental signature have been identified in the oases of the western Egyptian desert, while cobalt mines in Kashan (Iran) and in the Erzgebirge (Germany) are known to have been exploited during the later Middle Ages. For most of the first millennium BCE and CE, however, the identity of cobalt sources and their supply patterns remain elusive. The aim of this study is to characterise the chemical composition of cobalt colorants used during the first millennium CE. Compositional variations indicate the use of different raw materials and/or production processes, which in turn has implications for the underlying exchange networks. Using mainly correlations between cobalt, nickel and zinc as discriminants, our results show that the compositional signature of cobalt underwent two major changes. An increase in the CoO/NiO ratios occurs between the late fourth and the beginning of the sixth century, while a new zinc-rich source of cobalt begins to be exploited during the second half of the eighth century in the Islamic world.

Le recyclage du verre ne date pas de 1974, année où la première collecte en France de verres d’emballage est organisée en Haute-Marne. Si cette initiative est désormais intégrée à notre quotidien, elle n’est néanmoins qu’un jalon récent de l’histoire de cette pratique.À partir de plusieurs exemples de cargaisons antiques et byzantines chargées de verre brisé, de récits de vols de fenêtres et de vestiges archéologiques d’ateliers, nous proposons d’en retracer le cours, de l’Antiquité romaine au Moyen Âge.La physique et la chimie permettent désormais de reconnaître ces activités de recyclage à partir d’analyses de la composition élémentaire du verre, nous faisant cheminer à la croisée des sciences humaines et des sciences dures.