Archeological discovery confirms steel used earlier than first thought
A new archeological discovery has confirmed that tempered steel was used by artisans in the Iberian Peninsula to carve intricate motifs into hard rock stelae during the Final Bronze Age, earlier than previously thought.
Only fragments – no pun intended – of archeological history are known about western Iberia during the Final Bronze Age (FBA, 1,200 to 800 BCE) and the Early Iron Age (EIA, 800 to 600 BCE). The dating of stelae from the region, which feature carvings of anthropomorphic figures, animals, and images of weaponry, varies, with previous studies placing the stelae somewhere between the thirteenth and sixth centuries BCE.
Archeologists have conducted analyses of Iberian stelae and found that most had carvings that were made into extremely hard rocks. To date, there has been almost no research into the tools and carving technologies used to create these stelae, including using an expert stonemason to replicate the carvings and noting the differences between hard and soft rocks.
An archeological team led by Dr Ralph Araque Gonzalez has now examined the stone stelae from the Iberian Peninsula in south-western Europe to determine what kind of tools were used to make the carvings.
The stelae were first petrographically analyzed. Petrography is the study of rocks in thin sections by means of a petrographic microscope, an instrument that uses polarized light vibrating in a single plane.
Many of the stelae originated from the Sierra de la Moraleja, a long narrow elevation in the Badajoz region of Spain, and were found to be composed of hard quartz-sandstone common to the area. Two rocks, chosen for their compositional similarity to the original stelae, were used for the purpose of experimentation.
Analyzing an iron chisel found at a site in Rocha do Vigio in Alentejo, Portugal, the researchers determined it was made from 30% ferrite and 70% pearlite. Three reproductions of the chisel were forged, with one left in a soft state for comparison. The manufactured chisels were deemed suitable for carving into silicate quartz-sandstone.
The researchers tested the iron chisel, as well as chisels made from bronze alloys, on the replicated stelae. They found the bronze chisel could not penetrate the surface of the quartz-sandstone, whereas the iron "Rocha do Vigio chisel" produced an almost-exact replica of the original carvings.
Tools made from quartzite were also tested and discarded as tools that could have been used to carve the markings. Although the researchers could not prove metallographically that the chisel’s edge was made of hardened steel, experiments revealed that only hardened steel could successfully carve the stelae rock.
“The chisel from Rocha do Vigio and the context where it was found show that iron metallurgy, including the production and tempering of steel, were probably indigenous developments of centralized small communities in Iberia, and not due to the influence of later colonization processes,” said Araque Gonzalez.
The research shows a definite connection between stelae carving and iron metallurgy during the FBA-EIA. Considering all the tools available during that era, the researchers determined that the Iberian stelae could only have been carved using steel chisels.
The iron chisel found at Rocha do Vigio confirms that steel was available during the FBA, that is, 2,900 years ago. It had been assumed that steel production was impossible in the EIA and certainly not available during the FBA; that steel only came to be used in Europe following its invasion by Roman forces between 200 BCE and 14 CE.
“The people of the Final Bronze Age in Iberia were capable of tempering steel. Otherwise, they would not have been able to work the stelae,” Araque Gonzalez said. “This also has consequences for the archeological assessment of iron metallurgy and quartzite sculptures in other regions of the world.”
The study was published in the Journal of Archaeological Science.
Source: University of Freiburg