The Grez-Doiceau Merovingian cemetery contained numerous jewels, of which many were adorned with garnet. Their origin has been determined thanks to ion beam analysis carried out with the University of Liège cyclotron.

Before the opening of the building site which aimed at extending roadway RN25 as far as Grez-Doiceau in the Wallonia Brabant area, the Archaeological Department of the Walloon Region Ministry and the non profit making organisation ‘Recherches et prospections archéologiques en Wallonie’ (Archaeological Research and Prospection in Wallonia) hurried to the scene to carry out a preventative excavation of the site. It was thus that in 2002 one of the largest Merovingian cemeteries identified in Belgium was brought to light. The Grez-Doiceau site numbers over 400 graves, amongst which several belong to the highest ranks of the local aristocracy. Abundantly stocked, the site has given up numerous jewels, weapons, tools and containers made of ceramic, glass or metal. It thus bears witness to a long period of occupation which stretched from the end of the 5th century to the beginning of the 7^th century, thus covering the major part of the Merovingian era.

At first, the archaeologist in charge of the site’s excavation, Olivier Vrielynck, entrusted the study of the composition of the gold coins found on the site to the physicist François Mathis, from the University of Liège’s Centre Européen d’Archéométrie (European Archeometry Centre). These analyses, carried out with the ULg’s cyclotron, have enabled their parallel dating to be more sharpened or confirmed by numismatics. In effect, determining a coin’s composition, and in particular the proportion of gold it contains, contributes to identifying and dating it.



Over the course of discussions between the physicist and the archaeologist was born the idea of studying the chemical composition of numerous garnets contained in the Grez-Doiceau site’s jewels. These red semi precious stones were much used during the Merovingian era to make compartmentalised or cloisonné jewellery, very typical of the period: finely cut stones were placed into small metal cavities. This oriental style was spread into our regions during the time of the barbarian invasions. ‘This type of jewellery requires a constant supply of stones,’ explains François Mathis. ‘The stones could not be reused because the jewels were buried with their owner. This restocking of garnet constituted a large market at the time. Garnet is not a rare stone: it can be found almost everywhere, but the quality of the stones varies according to the place.’