The agreement also includes the sale of BHP’s San Manuel Arizona Railroad Company (SMARRCO).

The deal follows the company’s recent announcement that it is outlining plans to divest its ownership in around 10 undisclosed assets. The terms of the agreement permit Capstone to undertake environmental programs at the properties.

BHP Billiton copper president Peter Beaven noted that the deal signed for Pinto Valley is in line with company’s strategy and with this agreement the company has raised its transaction value to $5bn in last 12 months.

"We are pleased to have reached agreement with Capstone, particularly given their commitment to maintain our environmental and safety standards," added Beaven.

The deal, which is currently awaiting regulatory approval, is expected to be concluded in the second half of the 2013.

The company stated that its employees stationed at Pinto Valley and SMARRCO would become employees of Capstone as part of the transaction.

Pinto Valley located east of Phoenix in the Globe-Miami district of Arizona is estimated to produce 130-150 million pounds of copper in concentrate with production rate of about 10 million pounds of copper cathode a year.