The divestment follows the company’s sale of 40% interest in the Bengalla coal joint venture in Australia to New Hope for $606m in September 2015.
Rio Tinto copper and coal chief executive Jean-Sébastien Jacques said: "These agreements for over $800m in asset sales deliver significant value for our shareholders, with the potential for future royalties from Mount Pleasant.
"We believe Mount Pleasant can have a very positive future under its new owners with different priorities for development and capital allocation."
Since January 2013, the company has announced or completed $4.7bn of divestments in total.
The latest transaction, which is subject to certain conditions, including regulatory approvals, is expected to close in the second quarter of 2016.
The Coal & Allied-owned Mount Pleasant project is located adjacent to Bengalla mine and 4km from the town of Muswellbrook.
Coal & Allied has completed exploration, mining studies and an environmental impact statement (EIS) in 1997 upon securing an authority over the deposit in 1992. The development consent was granted in 1999.
Rio Tinto manages Coal & Allied’s operations in the Hunter Valley region of New South Wales, Australia. The operations include Mount Thorley Warkworth, Hunter Valley Operations and Bengalla.
Image: Rio Tinto’s Hunter Valley Operations in Australia Photo: Copyright © 2014 Rio Tinto.
