Mobility of Scandinavian commodities in the Middle Ages and modern period: identification of Norwegian whetstones in northern France, Belgium and the Netherlands

• Norwegian whetstones from medieval sites in northern France, Belgium and the Netherlands. • Whetstone trade supplied the North Sea basin from the Viking Age to the 20th century. • SEM observation and EDS analyzes confirm their Norwegian origin. • Phyllosilicates analyses discriminate Eidsborg from Mostadmarka. The sampling of several series of whetstones from medieval sites in the northern quarter of France and Belgium has revealed the (omni-)presence of specimens originating from Norway. This origin, assumed by macroscopic observation of the rocks, has been verified by previously unpublished EDS analyses acquired using the Scanning Electron Microscope (SEM). The rock is a fine ash-grey to green-grey micaceous quartz schist, rich in flakes of muscovite, chlorite and biotite, sometimes extending as far as the green-tinted quartz mica schist. The phyllosilicates bear a signature that ascertains their identification. The first Norwegian whetstones appeared in Western Europe with the arrival of the Vikings in the late 8th − 9th centuries, and the same supply seems to have lasted throughout the Middle Ages and the modern era. The production area of these whetstones is well known in the county of Telemark in Norway, where the exploitation of multiple quarries began in the Iron Age and ended around 1950. This study distinguishes Eidsborg stone from the macroscopically similar Mostadmarka stone, which crops out in the Caledonides region of western Norway and supplied whetstones from the 8th to the 11th century. The latter material appears to be absent from our collections, whereas the Eidsborg quarries supplied the French-Belgian region. These observations are in line with those made over the last decades around the North Sea basin, and illustrate that its southern part was connected to the same trading system. These discoveries shed light on an underestimated part of the medieval economy and reveal an exceptionally long-lived trading circuit.