Rinehart children's Roy Hill lawsuit to be fought in public

Gina Rinehart's bank account through her holdings in unlisted Hancock Prospecting are in the region of $17 billion.

While the slump in coal and iron ore prices would have certainly hurt her bank balance this year, a new lawsuit launched by her estranged children has the potential to do even more damage.

In the new federal court suit which is separate from the ongoing bitter battle over the family trust, Bianca Rinehart and John Hancock are challenging the ownership of mother Gina's most prized assets Hope Downs and Roy Hill.

Hope Downs is jointly owned with Rio Tinto and completed a 15 million tonnes per year expansion a year ago, but Roy Hill – a close to $10 billion project – is the real money spinner.

Roy Hill will start shipping 55-million tonnes-a-year as early as September 2015 and after securing the necessary debt package, Rinehart still holds 70% of the venture.

On Wednesday Rinehart Snr's lawyers lost a bid to keep court proceedings secret so as not to worry financiers or investors in Roy Hill about the real ownership of the project.

It not only has the potential to spill the beans on the inner workings of the secretive Rinehart empire, but derail what is currently Australia's largest mining project.