Rio Tinto has closed one of the main pits at its Diavik mine in Canada temporarily due to unstable ground.

The miner was made aware of subsidence on part of the road leading to the A154 underground area, one of the two major mining pits at Diavik, it told Rapaport News Monday. Subsidence causes a gradual caving, or sinking of an area of land, making it unsafe.

“On the evening of Thursday, July 4, an area of subsidence was detected on an access road to the A154 pit at the Diavik diamond mine,” a company spokesperson said. “All employees are safe, but as a precautionary measure, operations underground have been temporarily suspended in the A154 pit until we have a better understanding of the cause of this event.”

The miner declined to say how long the pit would be shut, or whether the closure would affect rough production from the deposit. However, subsidence usually requires structural improvements that could take time.

Diavik, which is Rio Tinto’s only diamond asset, is due to close in 2026. In April, the company reported a 22% drop in first-quarter output following a short halt to production to allow workers to grieve for colleagues who had died in a plane crash.

Image: The Diavik mine. (Rio Tinto)