Polymetal said on Monday that the Tomtor niobium and rare earth metals deposit in Russia's far east in which it holds a minority stake is one of the world's three biggest by reserves.
Tomtor is the key project in Russia's plans to boost output of rare earth metals, used in the defence industry and production of mobile phones and electric cars, to reduce its reliance on imports from China.
"Tomtor confirmed its scale and grade as one of the premier niobium and rare earths deposits globally," Polymetal CEO Vitaly Nesis said in a statement.
Polymetal, a major producer of gold and silver, owns a 9.1% stake in ThreeArc Mining, the firm developing the project. Russian businessman Alexander Nesis, Vitaly's brother, holds the largest stake both in the project and Polymetal.
ThreeArc will now start preparing a bankable feasibility study for the project, though difficulties with obtaining certain permits from the Russian government and engineering being delayed by the pandemic remain challenges, Polymetal said.
The Tomtor project has been delayed by six to nine months due to the pandemic, the silver miner said in January. It was previously expected to build a plant with annual production capacity of 160,000 tonnes of dry ore and to start production in 2025.
The initial estimate of Tomtor's ore reserves, conducted in accordance with the Australasian Joint Ore Reserves Committee (Jorc) code, showed that it contains 700 000 t of niobium oxide and 1.7-million tonnes of rare earth oxides, Polymetal said.
The Mt Weld in Australia and Kvanefjeld in Greenland are the world's other two top rare earths deposits by reserves.