Multimethod approach proves very early steel processing in the late Bronze Age
Freiburg, 22.09.2025
A research team from the University of Freiburg is using geological analyses, experimental archaeology, and 3D documentation to identify the manufacturing process of western Iberian stelae. New investigations confirm the results of an earlier study that already suggested the very early use of hardened steel 2,900 years ago.
An international and interdisciplinary research team led by Freiburg archaeologist Dr. Ralph Araque Gonzalez used a multi-method approach to investigate the manufacturing process of western Iberian stelae from the late Bronze Age and early Iron Age. This enabled the researchers to confirm the results of a study from 2023, which concluded on the use of hardened steel in the Iberian Peninsula as early as 2,900 years ago.
The scientists analyzed four stelae made of hard rocks such as silicate quartz arenite (quartzite), granite, and arkose using petrological investigations to determine rock microstructures and hardness. The team then produced replicas of the originals from the same rocks, allowing engravings to be compared and manufacturing processes to be simulated experimentally.
Detailed results were also provided by 3D scanning documentation, which calculated a below-millimeter-precise image of the engravings. These 3D models were converted into digital elevation models, which made it possible to measure exactly how deep, wide, or steep the lines were. This method was developed in collaboration with Maria Eugenia Polo from the Spanish University of Extremadura. “This multi-method approach allowed us to reconstruct the engravings very accurately. Through digital analysis, we were able to identify not only tool types, striking techniques, and manufacturing sequences, but also reveal misstrikes, wear, and resharpening,” says Araque Gonzalez. “At the same time, this approach also confirms what we were already able to hypothesize in 2023: only hardened steel could be used to make engravings on steles made of silicate quartz arenite at that time.”
“This multi-method approach allowed us to reconstruct the engravings very accurately. Through digital analysis, we were able to identify not only tool types, striking techniques, and manufacturing sequences, but also reveal misstrikes, wear, and resharpening.”
Dr. Ralph Araque Gonzalez
Project Manager, Institute for Archaeological Sciences (IAW), Department of Prehistoric Archaeology, University of Freiburg
Combination of methods enables precise engraving evaluation
The evaluation of 444 engraving profiles revealed that 94 percent of all engravings have profiles that can only be created by striking with sharp-edged tools. It often turned out that these were indirect strikes, which means that chisels and hammers or mallets were used. Bronze chisels with tin content between 10 and 16 percent became blunt or broke after a short period of use. Stone tools made of quartzite could be used to work softer granites to a limited extent, but had to be resharpened after a few minutes.
Engravings in silicate quartz arenite, from which over 20 percent of all known steles are made, were only possible with hardened steel.
“With our methodological approach, we can not only reliably reconstruct prehistoric stoneworking techniques, but also lay the foundation for gaining even deeper insights into the metallurgy and culture of past societies in future studies. That is why we now want to investigate how refined steel and different degrees of hardening have influenced the engravings and extend our multi-method approach to other stelae and rock art,” says Araque Gonzalez
Further information:
- Original publication Araque Gonzalez R., Polo M. E., Paniego Díaz, Rammelkammer V., Asmus B., Kaiser M. J., Richter A., Vintrici G., Ferreiro Mählmann R. (2025) Traceological analyses of tool marks on western Iberian stelae and their replications: Stones and steel at the end of the Bronze Age. Journal of Archaeological Science. First Release: 12. August 2025.
DOI: 10.1016/j.jas.2025.106340 - Dr. Ralph Araque Gonzalez is project manager of the DFG project “The Iberian Steles of the Late Bronze Age: Visual Arts, Technology, and Knowledge Transfer between the Atlantic and the Mediterranean” at the Institute of Archaeological Sciences at the University of Freiburg.
- The study was funded by the German Research Foundation (DFG project number: 446739573).