Rio Tinto Group has dug its last diamond and will close its final mine for the precious gemstone, marking the end of a business that lasted more than half a century.

The world's second-biggest miner said in a statement the Diavik diamond mine in the Northwest Territories of Canada had delivered final production with stones set to be cut and polished before final auctions.

Diavik was an engineering marvel as the mine was located under a frozen lake, and steep walls were required to keep the water at bay. The largest stone uncovered at Diavik was yellow and weighed in at 552.74 carats.

The closure will mean Rio has exited diamond mining entirely, as part of a broader plan to focus on key commodities including iron ore, copper, aluminum and lithium. The miner also plans to sell off its titanium and borates businesses as part of that strategy.

Rio has had a long history in diamond mining, first finding the gems in Western Australia's Kimberley region, which eventually led to the famous Argyle diamond mine that opened in the 1980s. The company's first discovery was made by geologists who found diamonds glinting in giant anthills at Argyle.

That mine was closed in 2020 and unlike Diavik, which produced predominantly white and yellow stones, delivered pink gems that fetched a significant premium.

Rio's diamond business floundered in recent years due to a supply glut and the ongoing impact of synthetic stones. It posted a US$79 million loss from the unit for 2025.

The world's biggest diamond producer, De Beers, has also struggled to sell stones at recent sales and has made sweeping cuts to its elite diamond-buying club.

"Forty years ago there were very few people who believed there were diamonds in Canada," Rio Tinto Iron & Titanium and Diamonds Managing Director Sophie Bergeron said in the statement. "To arrive at this milestone has required vision, courage and determination to overcome significant challenges to mine diamonds beneath a frozen lake in one of the world's most remote and pristine ecosystems."