The plunging iron ore price is wreaking havoc on Andrew Forrest's personal fortune, which has more than halved to just $2.8 billion and puts him outside of the top 10 richest people in Australia for the first time since 2006.

Mr Forrest, who is Fortescue Metals Group founder and chairman, was ¬confident the Pilbara miner could ¬withstand the weakening iron ore price and would continue providing capital for his philanthropic work.

"I didn't count it on the way up and I'm not counting it now," Mr Forrest told Fairfax Media on Wednesday.

"I can assure you that Fortescue ¬dividends will continue to support ¬philanthropic endeavours across Australia and around the world."

Shares in Fortescue Metals crashed 7.7 per cent on Tuesday to $2.74, a level not seen since the depths of the global financial crisis when debt-laden Fortescue was battling for survival. Fortescue share's have fallen 55 per cent since February, when Mr Forrest's stake was worth $6.2 billion.

The company was caught in a brutal sell-off of iron ore stocks, as the price of iron ore slumped 4.4 per cent to fresh five-year lows of $US71.80 a tonne. The price or iron ore has plunged 46 per cent this year, which is hammering the value of the miners. The value of Kerry Stokes's stake in Seven Group, which owns the WesTrac mining equipment business, has plunged $715 million to just $1.2 billion in the past 12 months. Seven Group shares dived 9.2 per cent to close at $5.90. Wealth destruction is being felt across the industry. John Grill, chairman at resources engineering and procurement contractor Worley¬Parson, has had his stake in the group slashed by $134 million to $307 million since August.

Mineral Resources managing ¬director Chris Ellison, who paid $57.5 million for the nation's most expensive home in 2009, had stock in the mining services company worth $307 million in March. It was worth $179 million on Wednesday.

Analysis by Fairfax Media shows $60 billion have been wiped off the value of 11 mining companies since January. BHP Billiton and Rio Tinto shares are proving more resilient in part because the big miners are ¬pushing operating costs lower, ¬offsetting a plunge created in part from their ¬massive mine expansions

BHP Billiton shares fell 1.5 per cent to $32.67 while Rio Tinto shares closed 2.5 per cent lower at $57.98. It is the smaller miners that are being hit hard because they are perilously close to break even point, or even losing money, with iron ore prices trading as low as they are. BC Iron shares fell 12.2 per cent to 57.5.¢, its lowest level in five and a half years.

Atlas Iron fell 4.65 per cent to 20.5¢. Between September last year and June this year Mr Forrest spent $70 million buying Fortescue shares, boosting ¬confidence in the stock that was being battered by a weakening iron ore price.

Mr Forrest declined to comment on whether he planned to buy any more Fortescue stock but said they did represent good value. He was also confident the miner would withstand pressures from the falling iron ore price.

"Fortescue has showed incredible competitiveness in developing the fastest iron ore construction the Pilbara has ever seen," Mr Forrest said.

"It is now turning that great management fire power to operating costs and you can look forward to Fortescue becoming even more competitive."

Gina Rinehart (whose fortune was estimated at $20.01 billion at the end of May) and Angela Bennett (valued at $1.55 billion) both receive royalties from Rio Tinto based on the revenue generated by the company's Hamersley Iron division.

The falling iron ore price will crimp this royalty in the coming years.