Rio Tinto has announced the start of commercial production at its A21 underground mine, part of the Diavik Diamond Mine in the Northwest Territories.
This marks the beginning of a new phase of operations at the site, which will extend the mine’s life until at least early 2026. The transition to underground production at A21 follows a $40 million investment made in February 2023, with a second phase recently approved with an additional $17 million committed.
Transition from Open Pit to Underground
The A21 pipe, which was first commissioned in 2018 as an open-pit mine, is the final pipe developed at Diavik. Rio Tinto’s move to underground operations is part of a strategy to extract additional value from existing resources. The A21 underground project consists of two phases. The first, now complete, included the construction of over 1,800 metres of underground tunnels to access the orebody. It is projected to produce an additional 1.4 million carats of diamonds. Phase two is expected to yield another 800,000 carats and will help maximise the value of the deposit before the mine’s closure.
“The A21 underground operation is positive news for our employees, partners, suppliers, and local communities in the Northwest Territories, as it will enable operations to continue through to closure,” said Diavik’s Chief Operating Officer, Matt Breen. “Rio Tinto’s decision to proceed with phase two is a testament to the excellent performance of our Diavik team in successfully developing the underground mine beneath the previously mined A21 open pit.”
Safety and Operational Milestones
Rio Tinto has emphasised the safe execution of the A21 underground development, noting that more than 100,000 labour hours were worked over 20 months of construction without any lost-time injuries. This highlights the importance the company places on safety, particularly in a challenging environment less than 150 miles south of the Arctic Circle.
The successful completion of phase one of the project ensures that Diavik remains one of Canada’s key diamond mines, having produced more than 144 million carats of rough diamonds since operations began in 2003. It is one of only three remaining active diamond mines in the country, alongside Ekati and Gahcho Kué.
Closure and Remediation Efforts
While underground production extends Diavik’s operational life, Rio Tinto is also preparing for the eventual closure of the mine. The company is already investing in closure readiness, including earthworks, site clean-up, and the procurement of necessary equipment. Progressive reclamation is part of this process, with Rio Tinto committed to restoring the site after mining ends.
Additionally, earlier this year, Rio Tinto completed the construction of a solar power plant at Diavik. The plant, which features bi-facial solar panels capable of generating energy from both direct sunlight and reflected light from snow, will supply up to 25% of the energy needed for closure activities. This shift towards sustainable energy reflects the company’s environmental commitments during the closure phase.
