Rio Tinto, the world's third-largest miner by market value, said it received a binding $340 million offer from industrial materials group Imerys for its talc business.
Selling the business is part of Rio's strategic plan to focus on large-scale assets. The miner has made divestments of more than $11 billion since 2008.
Rio Tinto Minerals, which includes the talc and borates business, posted a net profit of $199 million in 2010.
Last March, Rio told Reuters that it had restarted the process of selling its talc business and had received interest from a range of parties, including private equity groups.
Talc, the softest rock in the world, is used in animal feed, ceramic tiles, chewing gum and many everyday products including body powder.
Rio had put its talc and borates businesses up for sale in late 2008 but pulled it due to the global economic crisis.