Kvemo Bolnisi: From iron to copper in a 3,000-year-old workshop
In southern Georgia, a 3,000-year-old workshop called Kvemo Bolnisi has long puzzled archaeologists. Early excavations in the 1950s unearthed piles of hematite (an iron oxide mineral) and slag, which led researchers to declare the site an early iron-smelting workshop. New analyses, however, rewrite that history: the remains indicate copper was produced there, with iron oxide acting as a flux to increase copper yield. This nuanced reinterpretation reshapes our understanding of how the Iron Age began and where iron metallurgy first took root.
The new interpretation: iron oxide as flux in copper smelting
The key finding is that iron oxide was not being smelted into iron tools at Kvemo Bolnisi. Instead, workers likely used iron-bearing materials as flux within a copper-smelting furnace. Fluxes help manage the chemical environment inside a furnace, facilitating slag formation and metal separation. The presence of hematite and related iron minerals, therefore, signals deliberate experimentation with iron-bearing materials during copper production. In this light, Kvemo Bolnisi becomes a crucial case study in early metallurgical experimentation rather than a straightforward iron-producing site.
Why this matters for the origin of iron
This discovery feeds a long-standing hypothesis that iron metallurgy did not spring into full bloom with the Iron Age but emerged from the tinkering of metalworkers who already understood the properties of iron-bearing materials. If copper smelters were manipulating iron oxide within furnaces, they were collecting knowledge about iron-rich minerals that would later become ore for iron extraction. The Kvemo Bolnisi evidence does not claim iron production started here; it highlights a cognitive and practical bridge between copper technology and later iron smelting.
Context: iron in ancient technology
Iron artifacts appeared in Bronze Age contexts long before broad iron production transformed civilizations. The earliest iron objects were often meteoritic iron, a rare material prized for its extraordinary provenance. The shift to extractive metallurgy—smelting iron ore to produce workable iron—catalyzed monumental changes, from weaponry to infrastructure. Kvemo Bolnisi provides a tangible link in this continuum, illustrating how early metalworkers engaged with iron-bearing materials as part of refining metallic processes.
Methodology and publication
Researchers integrated slag analysis with modern geology and materials science to illuminate ancient decision-making. The study, titled Iron in copper metallurgy at the dawn of the Iron Age: Insights on iron invention from a mining and smelting site in the Caucasus, appears in the Journal of Archaeological Science. The work is supported by the British Institute of Ankara, the Gerda Henkel Foundation, and the American Research Institute of the South Caucasus, reflecting an international, interdisciplinary effort.
Looking ahead
Kvemo Bolnisi invites scholars to reassess copper-smelting sites across the Caucasus and beyond for signs of similar metallurgical experimentation. If iron oxide was used as a flux in copper production, other slag heaps may similarly contain traces of early iron thinking. By blending geology, materials science, and archaeology, researchers are rewriting not just a site’s history but the broader narrative of how humans first harnessed the iron in their world.
