Saturday, September 23, 2023

Archaeologists stunned by 2,900-year-old steel tools in Portugal

Amazing stuff! However, we learn little on how they produced this steel 

"... The study shows that steel tools were already in use in Europe around 2,900 years ago, during the Final Bronze Age. ...
The researchers conducted geochemical analyses on ancient Iberian stelaes -- upright monuments typically inscribed with information in the form of text, images, or a combination of the two -- and found these were made of silicated quartz sandstone.
“Just like quartzite, this is an extremely hard rock that cannot be worked with bronze or stone tools, but only with tempered steel,” ...
To confirm their hunch that these monuments were etched with steel tools, the researchers analyzed an iron chisel found in Rocha do Vigio, Portugal, which also dates back to the Final Bronze Age. They discovered that the chisel was made of heterogeneous yet astonishingly carbon-rich steel ...
The earliest known production of steel is seen in pieces of ironware excavated from an archaeological site in Anatolia (Kaman-Kalehöyük), which are nearly 4,000 years old, dating from 1800 BC. However, iron and steel didn't become abundant materials until around 500 BC when most Bronze Age civilizations collapsed, paving the way for the huge empires of Rome and Han China."

From the highlights and abstract:
"Highlights
• Protohistoric south-western Iberian stelae were often made from extremely hard rocks.
• The silicate quartz-sandstone stelae from Capilla could only be carved with hardened steel.
• Analyses of a Final Bronze Age iron chisel from Portugal revealed surprisingly high quality steel.
• The introduction of iron metallurgy represents a terminus post quem for stelae with this lithology.
Abstract
The south-western Iberian stelae from the Final Bronze Age (FBA) and Early Iron Age (EIA) have long been the centre of archaeological interest. These monuments show representations of human and animal figures, objects such as weapons, ornaments and chariots. Moreover, they provide insights into prehistoric stone working and sculpting techniques. On the downside, petrological studies of the rocks and consequent reflections on suitable tools are still the exception. Due to the lack of analysis and technological studies, this research will put emphasis on a multidisciplinary approach involving petrographic and metallurgic analyses, complemented by experimental archaeology.

Firstly, an accurate lithological determination of stelae from Capilla (Spain) has been established with petrographic methods. According to the results, two slabs for replications of stelae were obtained from the identified mono-mineral quartz-sandstone (“quartzite”) outcrop. The experiment involved the trial of chisels made from all expedient materials that were available in the FBA-EIA by a professional stonemason. Considering that such extremely hard rocks require robust tools for carving, a long ignored iron chisel from the FBA site of Rocha do Vigio (Portugal) was studied with metallography and exposed heterogeneous, however surprisingly high-carbon steel. The analysed rocks are amongst the hardest that can be used for sculpting, and in the course of the experiment, bronze and lithic tools could be discarded. The only tool that showed an effect was the replication of the steel chisel from Rocha do Vigio with a hardened edge. The distinct work traces were compared to the original monuments. We hypothesize that the production of carbon steel as well as its hardening were possibly already known at the FBA-EIA transition in Iberia. Hence, only the access to iron technology allowed for the making of stelae from the lithotypes that were frequently used in the Zújar basin around the municipality of Capilla."

"... The chisel is astoundingly well preserved and the corrosion layer is mainly superficial (Fig. 9, Fig. 11), with very little inter-granular corrosion into the sample ..."

Archaeologists stunned by 2,900-year-old steel tools in Portugal Steel tools were employed in Europe centuries before they became widespread during the Roman Republic era.


Fig. 9. The chisel from Rocha do Vigio, length ca. 18 cm 



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