Rinehart's estranged children, John Hancock and Bianca Rinehart, have launched fresh legal action, challenging the ownership of Hancock Prospecting.

Hancock Prospecting's key assets are stakes in the Hope Downs iron ore mine and the Roy Hill project, which is under development.

In a hearing in Sydney yesterday, lawyers for Hancock Prospecting and Gina Rinehart reportedly said details of the case should remain suppressed for commercial reasons.

According to AAP, Hancock Prospecting QC John Sheahan said there was "real risk of commercial harm" if details of the case were made public.

There is a temporary suppression order in place.

A spokesman for Hancock Prospecting said the company was focused on the development of Roy Hill, which continues ahead of schedule with more than 7200 people employed.

"It is a fantastic achievement to be currently ahead of schedule for a major resource project in Australia, with such an aggressive schedule," he said.

"In addition many thousands more jobs Australia-wide are supported by Roy Hill's works.

"It is a project for Australia of international significance being undertaken in increasingly difficult times for mining in this country.

"This action will be defended, and in the meantime work on the project continues despite distractions."

Roy Hill aims to put 55 million tonnes of iron ore into the market.

Earlier this week, Hancock Prospecting posted a full-year profit of $88 million from revenue of more than $2.6 billion.