Gina Rinehart's Hancock Prospecting doubled profits in 2016-17 to more than A$1 billion ($1.2b) as the Roy Hill mine finally hit full tilt, iron ore prices rose and a A$190 million donation towards building a hospital in Darwin was refunded.

And that's not all that's doubled. Rinehart's personal fortune has as well, to A$21.5 billion, according to new estimates by Forbes Magazine.

Financial statements for Hancock, which is a private company, were filed on Thursday and show a 142 per cent surge in net profit from A$443 million to A$1.07 billion in the most recent financial year.

The big driver was a huge jump in mineral sales, from A$1.9 billion to A$4.5 billion, thanks mainly to the Roy Hill project in the Pilbara region of Western Australia. It hit full capacity during last financial year - later than originally expected.

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"The Roy Hill project is now a contributor to Hancock's revenue and profit, and is largely responsible for the 160 per cent increase in revenue for the year," the company said in a media release.

Separate filings for Roy Hill Holdings showed it had posted a A$523 million net profit. Hancock Prospecting owns 70 per cent of Roy Hills Holdings.

Another major factor in Hancock's improved bottom line was a jump in the price of iron ore, which on average was 25 per cent higher than for the previous financial year.

Something the company didn't mention in its media release, but is disclosed in the filings sent to the Australian Securities and Investments Commission, was the benefit of a refund on a A$190 million donation towards building a new hospital in Darwin.

"As the development of this hospital is no longer proceeding, the donation was refunded during the year," Hancock Prospecting's financial statements say.

Hancock spokeswoman Sophie Mirabella said they couldn't wait forever.

"Considering the time that had lapsed and in light of the continued uncertainty around the project, the Rinehart Family Medical Foundation was not in a position to indefinitely hold significant funds for this specific project that was obviously not progressing, and regrettably could not proceed with this project," Mirabella said.

Hancock's media release made much of the tax paid by it and its executive chairwoman, who owns more than three-quarters of the company.

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"Mrs Gina Rinehart, personally and through the Hancock private group, pays more tax than any other Australian, and her private company Hancock is amongst the ranks of Australia's largest corporate taxpayers, as reflected in the publications of the Australian Taxation Office," the release said.

A trust whose beneficiaries are her children owns just under 24 per cent.

The financial statements showed beef sales jumped from A$12 million to A$55 million after buying two thirds of the Kidman cattle empire in the Northern Territory.

Rinehart has now reclaimed the title of richest Australian, according to Forbes, unseating property developer Harry Triguboff.