Geochemistry and the past: estimation of the output of a Germanic iron production site in the Netherlands

Abstract

The remains of large scale iron production in the Germanic settlement of Heeten (Prov. of Overijssel), dated from the late second to the fifth centuries AD, have been extensively studied. The timespan of the production is estimated at 30–35 year. A geochemical investigation of the ore and slags has proven to be of importance to the reconstruction of the smelting site. It is concluded that the bog iron ore must have been dressed carefully in order to concentrate the ore. The most conservative ore:slag:iron ratio is calculated to be 1.4:1:0.2 (by weight). Therefore, the site where the presence of a minimum of 45–50 tons of slag has been established represents at least 9 to 10 tons of iron. This suggests an annual production of 0.3 tons of iron, which far exceeds the need for iron for a rural settlement in that period. The large-scale production could be motivated by the historically known integration of the Salian Franks into the Roman Empire late in the first half of the fourth century [Groenewoudt and van Nie, (1995), J. Eur. Archaeol. 3, 187-215]. The fuel to ore ratio was assumed to be 1:1. Due to the charcoal production a large area around Heeten must have been deforested and the end of the iron industry could have been a result of fuel shortage.