Copper Ingots Buried Under a Malawi Tree Traveled 500 Miles From a Congo Mine
Lead isotopes trace a hoard found by a farmer in 1967 to the Kipushi deposit, pointing to a centuries-old trade route that likely ran by canoe down the Kafue and Zambezi rivers.
In 1967, a farmer in Malawi dug up eight copper ingots hidden beneath a large tree. Nearly six decades later, scientists have traced the metal to a mine about 800 kilometers, or 500 miles, away in what is now the Democratic Republic of the Congo, and in doing so have sketched out one of southern Africa's early long-distance supply chains.
The study, published in the Journal of Archaeological Science: Reports, focused on the five ingots that survive from the Chombe hoard; the other three have gone missing. They are X-shaped, like ingots found across Zambia and Zimbabwe and dated between the 14th and 18th centuries, but they are oddly light and rough. The researchers concluded they were not made by skilled metalworkers. Instead, someone appears to have pressed ordinary ingots into moist sand and poured copper into the crude impressions, producing thinner copies that lacked the originals' fine detail.
Why they were then buried is unknown. "It's a complete mystery," said Jay Stephens of New York University. "The fact that someone decided to hide these ingots under a large tree is quite curious. Perhaps they intended to come back for them, but never did."
Malawi has no copper ore of its own, so the metal had to come from elsewhere. Small deposits in neighboring Mozambique were little used, leaving the huge Copperbelt on the Zambia-Congo border and the old Kipushi mine near Lubumbashi as the likely candidates. To decide, the team measured lead isotopes, versions of the element that differ slightly in weight and whose mix acts like a fingerprint for each ore body. Stephens compared the mass spectrometer to a racetrack: the lighter isotopes, like a nimble sports car, hug the inside of the curve while heavier ones, like a school bus, drift outward. The isotopic signature matched Kipushi.
A direct overland route to Chombe was possible, but the researchers suggest traders more likely chose a longer, easier path of more than 1,000 kilometers by water. "Look at the trade route these ingots followed: from the copper mines of what is now the DRC, down the Kafue River by canoe, east along the Zambezi, then overland through Mozambique into central Malawi," said Smeda Matundu, chief curator of the Chichiri Museum. "That is not a random path; that is a deliberately engineered supply chain, centuries before the word 'logistics' existed." The authors note that the river route is a proposal and has not been confirmed.
The Chombe hoard may mark a stopping point on that corridor, roughly midway between the Copperbelt and the capital of the Maravi state in Malawi. The findings also lend weight to Chewa oral traditions holding that the Maravi founders migrated from the Copperbelt. "It's a proud moment for Malawian archaeology and a great reminder that our ancestors were far more connected to the wider world than is often appreciated," Matundu said. "Malawi has always been a trading nation."
