Gina Rinehart is digging what will likely be the world's last big iron ore mine for years to come in the Australian outback.

The timing couldn't be worse for the billionaire mining heiress given tumbling prices and oversupply, but the message for other iron ore miners is clear - the fight for survival is going to get more difficult.

Since construction of the $13 billion Roy Hill mine began four years ago in partnership with South Korean steelmaker POSCO , Japan's Marubeni Corp and Taiwan's China Steel Corp, iron ore prices have slumped 70 per cent and forecasters see worse to come.

Blueprints for new mines are being abandoned from Australia to Guinea, with a West Africa mine shelved this month after Ivan Glasenberg's commodities group Glencore conceded there was no prospect for a "profitable development".

"If someone was to walk up today and say 'I want to develop an iron ore mine,' you'd think they were crazy or know something others don't," said James Wilson, an analyst for Morgans Financial in Perth.

Analysts blame a massive rise in production on overestimates of China's appetite for imported ore by sector titans Vale of Brazil, Rio Tinto and BHP Billiton .

Together with Fortescue Metals, these companies added 234 million tonnes of iron ore in the past two years - five times yearly US consumption - and intend to inject another 196 million tonnes by 2020.

Their strategy is to eliminate competition, even it means driving down the price to the break-even point.

Enter Rinehart, whose Roy Hill mine will add another 55 million tonnes of high-grade ore.

Family dream

The nation's richest woman, Rinehart's estimated $14.8 billion fortune comes from royalties negotiated by her father, Lang Hancock, after he discovered vast iron ore deposits in 1952.

A mountain range and a rail line hauling iron ore across the outback bear the Hancock name, but the family never dug a mine of its own.

This time, Rinehart personally led the way in obtaining $US7.2 billion in debt funding for construction, finally securing a deal in March last year.

By September, Rinehart wants to see the first ore from the mine ready for loading.

"In terms of the iron ore price, I wish it was two years ago. All we can do is deal with the situation we have," said Roy Hill Chief Executive Barry Fitzgerald.

"There's no doubt both the shareholders and the financiers would like us very much to complete the project, to commission it and then ramp up as efficiently and as effectively as we can."

Ex-China advantage

Roy Hill hopes to set itself apart through its international partners, who hold a combined 30 per cent stake and plan to buy half the mine's output.

That cuts exposure to China, which accounts for the bulk of the world's seaborne iron ore market, but where signs are emerging that demand is peaking.

The mine should also benefit from the quality of its ore. About 60 per cent of the mine's yield will be in lump form, which fetches about a $US10 per tone premium over the benchmark as it requires less processing.

But the project still faces hurdles, with production costs likely to be above its larger rivals given the need to mine deeper to get at its ore, according to analysts.

"The trajectory of the iron ore price pretty much caught everyone by surprise, and Roy Hill is no different," said Patersons Securities analyst Rob Brierley. "They are putting on a brave face."

For rival producers, it will simply mean more supply.

Cliffs Natural Resources, which is trying to sell its only Australian iron ore mine because it can't compete, has no doubts about the wider impact.

"It's a bad time to bring a mine into a market that doesn't need more supply," said Lourenco Gonclaves, Cliffs CEO.

"Roy Hill's timing is bad, no, it is terrible."