Rio Tinto unit Rio Tinto Holdings Ltd. and Turquoise Hill Resources Ltd. agreed to off-load a collective 17.56% interest in Mason Resources Corp. to Mantos Copper (Bermuda) Ltd. for a total of US$2.7 million.

Under the terms, Rio Tinto Holdings will dispose of 7,455,058 Mason shares representing a 9.58% interest in the company, while Turquoise Hill will sell 6,209,699 Mason shares, reflecting a 7.98% stake in the company, at 20 cents apiece.

The transaction is expected to be completed within the next seven days and is part of Rio Tinto's ongoing review of its investment holdings, the company said Aug. 4.

Rio Tinto will no longer own any Mason shares after the transaction is completed.

Rio Tinto wholly owns Rio Tinto Holdings and indirectly holds a 50.8% stake in Turquoise Hill.