The development remains subject to receiving all relevant approvals, permits and licences and ongoing engagement with local communities and the Serbian government. There is some community opposition to the project due to heritage issues.

Jadar is one of the world's largest greenfield lithium projects with reserves of 16.6 million tonnes at 1.81% lithium and 13.4% boron, as well as an indicated resource of 55.2Mt at 1.68% lithium and 17.9% boron and an inferred resource of 84.1Mt at 1.84% lithium and 12.6% boron.

First saleable production is expected in 2026. Following ramp up to full production in 2029, the mine will produce about 58,000t of lithium carbonate, 160,000t of boric acid and 255,000t of sodium sulphate annually, making Rio a top 10 global lithium producer.

Rio expects to produce 2.3 million tonnes of lithium carbonate over the expected 40-year life of mine.

"We have great confidence in the Jadar project and are ready to invest, subject to approvals," Rio CEO Jakob Stausholm said.

"Serbia and Rio Tinto will be well-positioned to capture the opportunity offered by rising demand for lithium, driven by the global energy transition and the project will strengthen our offering, particularly to the European market. It could supply enough lithium to power over one million electric vehicles per year.

"The Jadar deposit and its unique mineral, Jadarite, discovered by Rio Tinto geologists in 2004 contains high-grade mineralisation of boron and lithium, supporting a long-life operation in the first quartile of the cost curve for both products."

Rio has carried out 12 environmental studies and more than 23,000 biological, physical and chemical analyses of air and water.

The proposed underground mine will use electric haul trucks, dry stacking of tailings and about 70% recycled water.

An environmental impact assessment will shortly be made available to the public for comment.

"We are committed to upholding the highest environmental standards and building sustainable futures for the communities where we operate. We recognise that in progressing this project, we must listen to and respect the views of all stakeholders," Stausholm said.

Construction is expected to begin next year, creating 2100 jobs during construction and 1000 jobs during operations.

"This is a significant moment for the lithium industry," Benchmark Mineral Intelligence managing director Simon Moores said.

"It marks the first time big outside money from a single miner or chemical maker has entered lithium and invested in an entirely new source."

"While expectation is that Rio Tinto will produce lithium carbonate at a run rate of 58,000 tonnes at full production, the strategy is usually more aggressive once proof of production is achieved and the product is accepted by battery and EV makers."