The agreement now includes a single payment on completion of $195.7 million, a conditional payment of $25 million, and royalties, payable quarterly at 2% of gross free-on-board revenue for coal sold from existing reserve estimates at prices exceeding $72.50/tonne.

This agreement reduces the total unconditional payments by approximately $3.3 million.

The proceeds of the sale will be used for general corporate purposes, Rio Tinto said in a statement.

As of June 30, the Mt Pleasant project had gross assets valued at $137 million and year to date profits of $243,000.

Rio Tinto also completed the sale of its interest in the Bengalla thermal coal joint venture in NSW for $617 million on March 1.