Rinehart's latest legal move means her kids probably won't see a dime of her $18 billion fortune

Perth-based Georgina Rinehart's true wealth is hard to guage as the vast majority of it is tied up in a private firm Hancock Prospecting which controls her empire, but the latest estimates put it at $18 billion and counting.

Rinehart's coal and iron ore wealth is also the subject of a bitter family feud. Three of her four children are currently suing her over control of the family trust.

The Herald Sun reports that through a clever legal move Rinehart on Wednesday ensured that the three – Bianca Rinehart, John Hancock and Hope Welker – would never see any real cash from the fortune.

Initially she moved the vesting date of the trust to 2068 when the children would be in their 80s, but now the provisions have been changed so that the trust vested on 30 April this year (also the 25th birthday of her daughter Ginia, who's the one not suing her.)

The Herald Sun explains what this means for the three other children:

The move means Mrs Rinehart can no longer use her own discretion to divide up the wealth of the trust as she sees fit, as was a condition of the 1988 Hope Margaret Hancock trust.

But as she controls 75 per cent of the family's premier mining company Hancock Prospecting, she can decide if they are to receive dividends.

If the children apply for their shares in the company, they could face multi-million dollar tax complications which may bankrupt them.

And even if they got control of them, they would be unable to sell the shares because of a deed that prohibits anyone but "lineal descendants" of Mrs Rinehart having ownership of Hancock Prospecting.

She now holds her children's 25 per cent share of the Hancock Prospecting empire in a "bare trust".

In January Rinehart also handed Ginia (sic) directorships of three companies, including Hancock Prospecting. The shake-up was the biggest in a long time at the Rinehart group of companies and elevated Ginia in place of her siblings to the top ranks in the world of mining.

Rinehart, 58, inherited Hancock Prospecting from her father Lang Hancock who discovered the world’s largest iron deposit in the Pilbara region in 1952.

When Rinehart took over 20 years ago following the death of her second husband (she has not remarried since) the family firm was debt-ridden and struggling and she built it into the world’s number one private mining business.

Hancock Prospecting has prospered mainly thanks to royalty streams from Rio Tinto's operating iron ore mines in the Pilbara. Rinehart in April announced that she is taking Rio to court to seek 2.5% of sales from two additional mines in the region.

Some predict that Rinehart, a vociferous opponent of Australia's carbon and mining taxes, would become the world’s richest person as her coal and iron projects start producing by 2014 and earn her annual profits of as much as $10 billion.

Although the publicity-shy Rinehart has never granted a media interview, she has invested heavily in media and in February Rinehart increased her newspaper and television investments in Australia prompting one observer to comment that Big G is “gonna be the whole shooting match”.

Big G, as she is sometimes referred to in the media, ranks number 4 on the MINING.com 2012 list of mining billionaires.

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