Analysis of a “rusty treasure” excavated during industrial gravel extraction at Deinham, Austria reveals it is the largest mass find of prehistoric iron bars in Europe, pointing to iron production and trade during the Iron Age on an unprecedented scale.
During the Late Iron Age La Tène period (mid fifth–first centuries BC), Europe saw a vast increase in iron production, with huge quantities and varieties of iron objects becoming common across the continent.
Despite knowing iron was produced at dedicated iron-production centres, the exact scale of the trade is poorly understood as iron semi-products often escape the attention of finders and are difficult to date precisely.
Therefore, the discovery of numerous double-pointed iron objects during gravel extraction along the River Danube provided a unique opportunity to investigate large-scale prehistoric iron production and trade.
“It is nothing short of a minor miracle that the largest mass find of prehistoric iron bars in Europe did not end up at scrap dealers, but was reported to the Austrian monument authority”, says lead author of the research, Professor Peter Trebsche from the University of Innsbruck. “I am sincerely grateful to the finders that they decided to donate this extraordinary trove to a state museum collection.”
Professor Trebsche and Dr Marion Berranger from the Université de Technologie de Belfort Montbéliard analysed and radiocarbon dated the find, concluding that it is a huge assemblage of iron bars dating to the La Tène period.
Comprising at least 500 iron semi-products together weighing more than one tonne, the Deinham mass find is the most abundant assemblage of Iron Age bars currently known in Europe.
Likely lost in a shipwreck, the iron was probably being transported down the River Danube for trade, highlighting the large-scale, well-organised inland shipping capabilities of later prehistoric Central European societies.
The primary destination of the iron bars remains unknown, but they were likely forged in Bavaria, where several iron-production sites have been found in the vicinity of oppida: Iron Age Europe’s iconic large-scale fortified towns.
“The iron semi-products found at Deinham weigh around one tonne of iron, which is enough to forge approximately 500 swords with an average weight of 1.5–2kg”, Trebsche explains. “Even if we take material losses during manufacture into account, the iron from Deinham would have been sufficient to equip a large group of warriors with weapons.”
The cargo’s value must have therefore been immense.
The La Tène period is known for its large hoards of gold coins, such as the 443 coins totalling 3.7kg of gold found at the major oppidum of Manching in Bavaria. Manching is located near to a large iron mining area, from which the iron for the bars could have been sourced.
These coins could have plausibly been equivalent in value to a tonne of iron, so it is possible that transactions of this scale were facilitated by increasing monetarisation during the La Tène period.
"It is incredible that such a large quantity of iron was transported at once and was available in a single exchange transaction in the Late Iron Age”, Trebsche concludes. “This finding demonstrates the increased capacities of iron production that were reached in the 3rd/2nd century BC in the Danube region.”