Gina Rinehart yesterday sought to reclaim a stake in the potentially multibillion-dollar Rhodes Ridge mine, in the latest turn in the ongoing feud between WA's two mining dynasties.
Hancock Prospecting alleged in the Court of Appeal yesterday that a 2010 Supreme Court decision wrongly ruled that it should hand over its 25 per cent share of the undeveloped Pilbara mine to Wright Prospecting.
Justice Michael Murray had ruled two years ago that Wright Prospecting had rights to 50 per cent of the mine - the other half belonged to Rio Tinto - because of a 1984 agreement between Lang Hancock and Peter Wright.
The decision wiped $530 million from Mrs Rinehart's personal wealth and billions in potential earnings from the undeveloped high-grade iron ore mine.
The 1984 agreement was a bid by business partners and life-long friends, Mr Hancock and Mr Wright, to carve up their complex web of assets and keep their heirs out of court.
But it has since proved futile, with Mrs Rinehart spending more than a decade disputing the matter with Wright Prospecting heirs Angela Bennett and her recently deceased brother, Michael Wright.
Hancock Prospecting yesterday filed 23 grounds for appeal against the 2010 decision, primarily involving claims that agreements between the two men were ambiguous and open to interpretation.
Barrister Steven Finch SC agreed that the 1984 agreement had listed Rhodes Ridge as one of the assets that would eventually fall to Wright Prospecting.
However, the mining partners had agreed in a contract to keep Rhodes Ridge and other assets temporarily under joint control, so as not to upset joint venture partners.
He said the contract stated that Wright Prospecting could assert its right to ownership by "pressing the button" on a certain clause.
This clause involved getting ministerial consent for the change in ownership. Mr Finch said Wright Prospecting failed to get State Government consent before lodging a writ in 2000, which made its bid for ownership invalid.
Mr Finch also argued yesterday that Justice Murray had been wrong to rule invalid a separate agreement from 1989.
This agreement followed Mr Wright's death in 1985, and outlined moves by Mr Hancock to sell Rhodes Ridge to a third party and share the proceeds between both mining dynasties.
Justice Murray had earlier ruled that the validity of this agreement died with Mr Hancock in 1992.
But Mr Finch said it was still valid, and was proof that Hancock Prospecting had a permanent stake in mine.
Rhodes Ridge has proven a source of hot dispute, with iron ore company Cazaly Resources seeking in a separate court case to wrest control of the mine under the State's so-called "use it or lose" legislation.
Wright Prospecting has indicated that it may sue for royalties from the Hope Downs iron ore development. The case continues today and is expected to end on Friday.