Les sources de l’or du décor entre Orient et Occident (IVe-XIIe s.)

The paper explores the source of gold in the gold mosaics between fourth to twelve century, one of the best expression of Byzantine and early Islamic art. Many historical and technical issues point to the use of coins to make the gold leaves used in the tesserae. Not only the dynamic of the circulation of gold, strictly controlled, but also the relatively important quantity of gold used and the indications of the medieval recipes suggest the use of monetary gold to produce gold leaves. The archaeometric analyses performed in the Western and Eastern sites show a good match between circulating monetary alloys and the gold leaf compositions until the sixth century and, together with the type of glass, can provide criteria to date the tesserae. A diversification of the supply is also displayed from the eight century.