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Copper climbed back to within half a cent of its record high on Tuesday as an outage at the smelter that processes ore from the giant Grasberg mine compounded a supply squeeze that has held London benchmark prices above $14,000 a tonne for an unprecedented run of sessions, while aluminum jumped to a seven-week high after a Brazilian alumina plant halved output.
Copper for September delivery touched $6.7005 a pound ($14,772 a tonne) on the Comex, four-tenths of a cent short of the $6.7045 record set on August 5, before easing to $6.6360, up 0.3% on the day. The December contract traded as high as $6.7980, and further out the curve, copper for delivery in the second half of 2027 changed hands above $7 a pound.
On the London Metal Exchange, three-month copper was little changed at $14,195.50 a tonne, leaving the Comex premium at about $435. Cash metal settled $138 above the three-month contract on Monday, the widest premium on near-term deliveries since October and a textbook signal of physical scarcity. Benchmark prices first topped $14,000 a tonne early this month. LME warehouse stocks fell another 4,675 tonnes on Monday to 218,300 tonnes.
Buyers of copper from the Gresik smelter in Indonesia were told the plant will be shut for assessment and repair over the coming weeks after a boiler leak on August 8, Bloomberg reported. Gresik processes ore from Grasberg and is operated by PT Smelting, jointly owned by Mitsubishi Materials and PT Freeport Indonesia. Mitsubishi confirmed operations are suspended with no restart date decided.
Freeport’s own Manyar smelter in East Java is due to resume production in September, with the two plants together expected to turn out close to 400,000 tonnes of cathode this year, while the Grasberg mine is still recovering from last September’s fatal mudslide and is not targeted to reach full production until the end of 2027.
Alumina shock
Aluminum rose as much as 1.9% in London and was trading 1.7% higher at $3,373 a tonne after Norsk Hydro said its Alunorte refinery in Brazil, one of the world’s largest sources of alumina, had cut output to half of capacity when a supplier flagged disruptions to natural gas availability. Alumina futures closed 1% higher at 2,724 yuan a tonne in Shanghai.
The Middle East accounts for roughly a tenth of global aluminum output and flows have been disrupted since the Iran war began, draining LME inventories to about 255,000 tonnes, the lowest since November 1990. Hydro warned last month the annual global shortfall could widen beyond 900,000 tonnes if Strait of Hormuz traffic is not normalized.
“Negotiations in the Middle East are not proceeding smoothly, which should provide some support for aluminum prices,” said Yan Weijun, head of nonferrous metals research at Chinese trader Xiamen C&D, in a Bloomberg note.
Elsewhere on the LME, tin held near $55,750 a tonne for a 37% gain in 2026, zinc slipped to $3,728 and lead was steady at $1,908. Nickel was the laggard, down 1% at $16,782 and barely changed for the year.
Miners go the other way
Freeport-McMoRan fell 3% in New York, Lundin Mining 3.8% and First Quantum Minerals 1.8%, while Vale dropped 3.9%. Southern Copper, which went ex a 1.012-for-1 stock split on Tuesday, was down 4.5%. Teck Resources fell 1.2%, Ivanhoe Mines was little changed and Glencore added 0.6%. In Asia, Zijin Mining shed 6% and Jiangxi Copper 3.5%. The S&P 500 was down 0.3% and the materials sector eased by a similar margin.
Copper is up nearly 18% in 2026 and has gained roughly half its value in 12 months.
(With files from Bloomberg)
