Over 10,000 years ago, peoples around the Mediterranean basin were hammering unheated rock rich in pretty green copper ore and making objects with it: beads, pendants and other small ornaments. After thousands of years of hammering, people began heating tiny amounts of copper ore in small clay pots called crucibles, producing metal. Now, Israeli archaeologists report on evidence of the next stage: a furnace smelting, dating to about 6,500 years ago in Be’er Sheva – using ore imported from Wadi Faynan in Jordan, more than 100 kilometers distant.
The discovery of fragments of furnaces, crucibles and slag from a big copper smelting workshop at the Horvat Beter archaeological site was reported by Prof. Erez Ben-Yosef, Dana Ackerfeld, Omri Yagel of Tel Aviv University, Dr. Yehudit Harlavan of of the Geological Survey of Israel and Talia Abulafia, Dmitry Yegorov and Yael Abadi-Reiss of the Israel Antiquities Authority and colleagues in the Journal of Archaeological Science: Reports.
The team isn’t asserting that furnace smelting was invented in the Be’er Sheva Valley or even the southern Levant, but that their find, a fixed (immovable) furnace made of clay built into the ground, is one of the earliest of its kind. Others from the era have also been found in the Be’er Sheva area. The workshop employed a sophisticated two-stage process: furnace-based primary smelting of the rock, followed by further melting or refining of the metal in crucibles.
The furnace technique could produce larger amounts of product compared with wee crucibles, but note ye that it still didn’t have any pragmatic application – if only because copper is too malleable.
“They say necessity is the mother of invention," Ben-Yosef tells Haaretz. "We need a better weapon so we invent a new material. But the story of metal shows it isn’t necessarily so.” Metal might have filled a need, but it wasn’t a material one, rather something more esoteric. “It started with an aesthetic. For thousands of years the use of metals was nonfunctional, not to do with material improvement,” he says.
He also believes that the development and progress of metallurgy didn’t happen by chance. “They were the result of prehistoric R&D by groups of people as curious as we are today, investing time. Scientific exploration wasn’t invented today – it’s human nature,” Ben-Yosef says. “Human nature is to be curious and to explore. Society encouraged them to explore, to find new cool stuff.”
The primal technique of crucible smelting involved putting bits of copper ore into a small clay pot, adding charcoal, and igniting it to melt the copper out of the rock. The pot wasn’t covered. The embryonic metallurgist would blow air into it to raise the temperature, Ben-Yosef explains: “It was a kind of very small portable furnace.” The earliest evidence of crucible smelting was found in Anatolia and Iran, dating to the late sixth millennium B.C.E.
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The earliest furnace was slightly bigger and was a fixed structure, not a portable one, built into the ground with an elevated rim, he explains.
Not all scholars agree that the advance from a portable tiny crucible to a fixed slightly bigger furnace was a huge step forward, he adds, but leaving the nomenclature of the step aside – technically, a furnace is a big crucible stuck in the ground, he sums up.
So the crucibles and the furnace were both made of pottery. The ore has to be heated to at least 1,200 degrees Celsius to melt out the copper, Ben-Yosef says. Asked about the melting temperature of the pottery vessels, he explains that the ancients tempered the clay (adding other substances) to make it more heat-resistant. Indeed, much investment in R&D was likely made, given that the technique of potting had only reached the Levant one or two thousand years before this advent of metallurgy.
Elaborating on the R&D aspect, Ben-Yosef stresses that you can’t just take copper ore, throw it onto an open fire and expect anything much to happen. It’s not hot enough. A bonfire on the beach may reach 500 degrees Celsius, which isn’t even halfway to copper melting temperature. You need to control the oxygen flow, he explains.
These early metallurgists in the Be’er Sheva Valley and the southern Levant in general are associated with the so-called Ghassulian culture of the Chalcolithic period, which existed about 6,500 to 5,800 years ago and spanned from the Upper Galilee and Golan in the north to the Judean Desert and the northern Negev in the south. The Ghassulian culture still used stone tools for everyday use, and also smelted copper – which at least some of them crafted magnificently. In 1961, archaeologists discovered a cache of gorgeous copper statuettes, bowls and other artifacts in a cavern overlooking Nahal Mishmar, a stream that flows into the Dead Sea that dated to about 6,500 years ago.
So from the primordial stage of banging a rock and winding up with a pretty shiny substance that could be hung from the neck, the Be’er Sheva find indicates that by around 6,500 years ago, there was a high degree of craft specialization, the team suggests. That speaks to the social organization of the people living in the region.
How likely is the Be’er Sheva furnace to be the first-ever? Maybe earlier ones will be found one day – Ben-Yosef notes that the evidence of ancient metal production is very fragmented and easy to miss. In any case, the consensus among researchers is that metallurgy was invented once and then spread, and that it wasn’t a case of convergent evolution. “After hundreds of years of making pottery and plaster, they had the background,” he says. “The R&D people were on the threshold of this invention and once invented there was a constant effort to improve the technology, to make bigger quantities in each smelting cycle, to make the process more efficient. The technological evolution varies by region. After several hundred years of using crucibles, some places introduced furnaces, possibly in Be’er Sheva for the first time. Then they spent thousands of years perfecting the technique.”
By the time of the so-called King Solomon’s Mines in Timna 3,000 years ago, the technology was almost unrecognizable. If a crucible could produce perhaps 20 to 30 grams of copper in each smelting cycle of three to four hours, an Iron Age smelting furnace could produce several hundred grams – larger by an order of magnitude.
Finally, isotopic analysis nailed down the source of the ore the ancient Be’er Shevans were smelting to Jordan. One wonders why the furnace wasn’t built by the mine. The answer likely lies in trade – and secrecy. The inventors or possessors of the breakthrough technique were guarding it as jealously as we guard industrial secrets today.