Rio Tinto plc (RIO) Stock Price Slips as Boyne Smelter Support Fails to Offset Mining Selloff

March 26, 2026
Rio Tinto plc (RIO) Stock Price Slips as Boyne Smelter Support Fails to Offset Mining Selloff

London, March 26, 2026, 11:30 GMT

Rio Tinto plc shares in London slipped to 6,362 pence early Thursday, down from their last close at 6,563 pence. Shares saw action between 6,345 and 6,448 pence, keeping the stock far off its 52-week peak of 7,557 pence. 1

Why does it matter? Rio is pushing further into aluminium and copper, aiming to cut back on iron ore dependence at a time when governments are moving to support smelters and regional aluminium prices are getting squeezed. Back in February, Rio pointed out iron ore would still make up roughly 60% of group earnings in 2025. Copper? About 30%. 2

Australia’s federal and Queensland governments are putting up A$2 billion over the next decade to back Boyne Smelters, a move Rio says should help the Queensland facility stay competitive after its current power contract ends and keep aluminium output alive through at least 2040. “This partnership will ensure Boyne Smelter remains internationally competitive,” Aluminium & Lithium chief executive Jérôme Pécresse said. 3

That timing coincided with a swing higher in aluminium prices across Asia. Japanese buyers locked in premiums of $350 to $353 per metric ton for shipments covering April through June—the steepest in more than a decade. Producers in the mix included Rio and South32. The premium marks the regional standard over London Metal Exchange cash prices. 4

Copper buys Rio more time, but the short-term view is anything but clean. Katie Jackson, head of Rio’s copper unit, said the company was “quite committed” to moving Resolution Copper forward “as quickly as we can.” The plan is for the Arizona project to be online in the early-to-mid 2030s. Still, she noted that current U.S. market conditions “don’t support the Kennecott smelter.” Treatment and refining charges—what smelters get for converting concentrate—have dropped below zero as concentrate becomes harder to find. Rio, meanwhile, has kicked off a $500 million drilling push at Resolution. 5

That goes some way toward clarifying the choppy action in the stock. Last year, copper pulled in twice the profit for Rio, yet iron ore remains the main engine for both cash flow and payouts. Aluminium and lithium fill in the gap. 2

Rio’s shares weren’t alone in slipping. Anglo American, Glencore, and BHP all traded lower than their prior closes in London on Thursday morning, signaling selling pressure hitting the major miners, not just Rio. 6

Yet risks linger for the company. Jackson flagged that Kennecott’s underground mine is staying shut for several weeks following a worker fatality. Resolution might also have to ship out copper concentrate, given soft U.S. smelting margins. And for Boyne, the outlook still hinges on the rollout of renewable power Rio is backing in Queensland. 5

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