Rio Tinto says it has approved a $40 million investment in the first phase of underground mining below the existing A21 open pit at its Diavik Diamond Mine in the Northwest Territories of Canada.

Based on the updated mine plan and production schedule including the A154N and A154S pipes, and subject to approval of the second phase of the A21 underground project, Diavik is now expected to end commercial production in the first quarter of 2026.

Phase 1 of underground mining of Diavik’s A21 pipe is expected to deliver an additional 1.4 million carats of rough diamonds. Current employees and contractors will be transitioned from other areas of the mine for both the construction and production phases of the project.

Diavik expects to seek approval for Phase 2 of the A21 underground project in the first half of 2024. Phase 2 is expected to deliver an additional 0.8 million carats of rough diamonds.

Sinead Kaufman, Chief Executive of Rio Tinto Minerals said: “Rio Tinto’s decision to support the underground development of the A21 pipe was prefaced on compelling industry fundamentals, our proven capacity to safely develop diamond mines in extreme conditions and a track record in competing successfully in the global diamond industry. This is good news for our employees, partners, suppliers and local communities in the Northwest Territories.”

The Diavik mine, 100% owned and operated by Rio Tinto, is Canada’s largest diamond mine in terms of production with 6-7 million carats of rough diamonds produced each year. Since mining began in 2003 Diavik has produced over 100 million carats of diamonds. Construction of the A21 open pit commenced in 2015 and it was finished safely and ahead of time to commence commercial production in 2018.