Potanin will pay $6.5 billion in cash and transfer his 35.2% stake in Polyus Gold, worth $3.5 billion at the current share price, in exchange for the stake in Norilsk Nickel. The deal is to be finalized before November 15, Onexim said.
Interros earlier said that Potanin held about 30% of shares in Polyus Gold while Prokhorov's stake in Russia's largest gold miner was also estimated at around 30%.
In April, Russia's United Company RusAl, the world's largest aluminum producer, finalized a deal to buy a blocking interest of 25% plus one share in Norilsk Nickel from Prokhorov.
The Russian market has reacted swiftly to the news.
Norilsk Nickel's shares closed more than 6% up in the Russian Trading System on Tuesday compared with a 2% drop in the RTS overall index on Monday.
On the London Stock Exchange, Norilsk Nickel's stock went up almost 6% on Monday's close and Polyus Gold appreciated 2.7%.