Rio Tinto is set to drag Australia's richest woman back into the courtroom, after challenging a court order to pay Gina Rinehart's Hancock Prospecting and a third company close to $200 million.
Confirmation that Rio will appeal against the New South Wales Supreme Court ruling came amid an upbeat set of June quarter results that prompted strong buying of Rio shares late on Tuesday.
NSW Supreme Court Justice David Hammerschlag told Rio in May that it should have been paying royalties to companies controlled by Mrs Rinehart and fellow mining heiress Angela Bennett based on a 43-year-old agreement involving the fathers of the two women.
Hancock launched the action against Rio despite the two companies holding a long-standing iron ore joint venture in the Pilbara that delivers most of Hancock's revenue.
After considering its legal options for several months, Rio said on Tuesday that "a notice of intention to appeal has been filed in respect of the court's decision".
Rio has set aside $US183 million to cover any possible liability.
The dispute is separate to another long-running legal battle between Hancock and Ms Bennett's company Wright Prospecting, which is debating the ownership of lucrative iron ore tenements in the Pilbara.
Hancock Prospecting is the biggest shareholder in Fairfax Media, owner of this publication.
Meanwhile, the 51.8 million tonnes of iron ore that Rio produced in the June quarter was narrowly better than most analysts expected, particularly given recent interruptions from rain and equipment failures.
It enabled Rio to maintain its full-year guidance of 265 million tonnes of iron ore in 2013, including volumes owned by joint venture partners.
There was good news from Rio's copper division, which reported that the recent wall collapse at the Kennecott Mine in the US would not dent copper production as much as first thought. The amount of copper mined will now be 100,000 tonnes less than original guidance, rather than 125,000 tonnes as feared.
Arguably the biggest dilemma facing Rio in 2013 is whether to spend $US5 billion expanding its iron ore mines to take production up to 360 million tonnes a year.
The project has come under intense scrutiny from investors who question whether Rio should be spending such large amounts of money during an austerity drive.
On Tuesday, Rio said the expansion to 360 million tonnes was "currently under way", but there was no new commitment to spending and its rhetoric around the expansion was slightly different to before.
Rio shares had spent much of Tuesday below Monday's closing price, but finished the day 75¢ higher at $55.52.
Rio's old rival BHP Billiton will reveal its June quarter results on Wednesday morning, while fellow Pilbara iron ore miner Fortescue Metals Group will report next week.