Oyu Tolgoi, in southern Mongolia just north of the Chinese border, is key to Rio’s efforts to move beyond its dependence on iron ore and expand in copper, the metal that underpins the clean energy transition.

As demand for copper surges, supply is increasingly likely to come from mines like this one on the arid steppe: expensive, technically complex, outside traditional copper jurisdictions and operating under the eye of governments jealously guarding their natural resources.

“There’s a huge crisis,” said Doug Kirwin, one of the earliest geologists to work at the deposit that became Oyu Tolgoi, or Turquoise Hill, named after the area’s rocks, stained by oxidised copper.

“There’s no way we can supply the amount of copper in the next 10 years to drive the energy transition and carbon zero. It’s not going to happen,” added Kirwin, now an independent consulting geologist.

Analysts at Wood Mackenzie estimate a greener world will be short about six million tonnes of copper by the next decade, meaning 12 new Oyu Tolgois need to come online within that period.

But they aren’t – there are simply not enough new mines, much less enough large ones. The result is a gap: BloombergNEF estimated appetite for refined copper will grow by 53% by 2040, but supply will climb only 16%.