A 3K-year-old copper smelting site could be key to understanding origins of iron

Summary

Copper smelters at the site used copper ores that lacked iron. Adding the iron oxide hematite to the furnace helped the copper metal to separate more easily from the impurities in the ore. Credit: Dr. Nathaniel Erb-Satullo Research from Cranfield University sheds new light onto the transition from the Bronze Age to the Iron Age, showing how experimentation with iron-rich rocks by copper smelters may have sparked the invention of iron. Published in the Journal of Archaeological Science, the work reanalyzed metallurgical remains from a site in southern Georgia: a 3000-year-old smelting workshop called Kvemo Bolnisi. During the original analysis in the 1950s, piles of hematite (an iron oxide mineral) and slag (a waste product of the metal production) were found in the workshop. Finding those iron oxides, the original excavators thought the workshop was an early iron smelting site. However, new research shows that those assumptions were wrong. Rather than iron, workers at Kvemo Bolnisi were smelting copper using iron oxide as a flux—a substance added into the furnace to increase the resulting copper yield. These discoveries give weight to a long-discussed theory that iron was invented by copper smelters. This evidence shows that ancient copper metalworkers experimented with iron-bearing materials in a metallurgical furnace, which was a crucial step towards iron smelting. Sparkly hematite mineral was used as a flux by copper smelters. Its distinctive appearance may have helped to attract attention from ancient miners and prospectors. Credit: Dr. Nathaniel Erb-Satullo The importance of iron While the Iron Age marked the beginnings of widespread iron production, the metal itself wasn't a new discovery. Iron artifacts have been found dating from the Bronze Age, most famously an iron dagger with a gold and rock crystal hilt from the tomb of Egyptian king Tutankhamun. But the earliest iron objects were forged from naturally occurring metallic iron found in meteorites, not ext...