The plunging iron ore price could force high-cost mines in Western Australia to shut by July, according to senior mining executives and analysts.

The price of key steel-making ingredient crashed below $US60 a tonne overnight on Thursday to the lowest level since May 2009, when daily prices became the benchmark pricing system.

It adds further pressure to miners that have been dramatically cutting costs for the past six months.

Perth-based Patersons Securities head of research Rob Brierleysaid the sustained price rout would trigger miners to scale back or mothball mines.

"We have been dealing with this iron ore price for the best part of six months so it would be starting to hurt them," Mr Brierley said.

"The next stage would be starting to look at rationalising production and scaling it back. I would expect that to be the next phase; high-cost mines shuttering and lower-cost mines being worked harder."

He said this may happen by July.

"All of them are letting people go and doing everything from a cost perspective but sooner or later you squeeze that lemon until there is no juice left," Mr Brierley said.

"I don't see the iron ore price getting any better."

Traders are nervous demand for iron could soften after China set its lowest target for economic growth in 15 years.

Mothballing

The sustained iron ore price rout is heaping enormous pressure on the nation's miners, which have been slashing costs for nearly a year to preserve profits. Most are now loss-making.

Resources consultancy Wood Mackenzie warned Mineral Resources' Carina mine, 400 kilometres east of Perth, was one of three mines at risk of closing if the price remained about $US60 a tonne or lower.

Mineral Resources chairman Peter Wade said the company, which also operates mines for other miners, would re-evaluate Carina's operations after the iron ore price slid below $US60 a tonne.

"The board has a look at these things every meeting and certainly Carina has higher operating costs than Iron Valley primarily because we don't own the associated infrastructure," Mr Wade said.

"We are looking at it closely but the board hasn't made any determination that we would be mothballing that plant right now but certainly the price change over night means it needs to be looked at again."

The price fall coincided with iron ore juniors BC Iron, Mount Gibson Iron and Atlas Iron being removed from the S&P/ASX 200 index.

Their share prices have fallen 90 per cent, 70 per cent and 82 per cent respectively in the last 12 months, pushing their market value below cash on hand.

Perth-based Argonaut resources analyst Matthew Keane said most miners were struggling.

"The reality is most of the miners, other than BHP and Rio, are in a loss-making position," Mr Keane said. "Fortescue Metals Group is operating on slim margin. They are right on the knife-edge at these prices."

Atlas wobbly

Atlas could close its Abydos mine to preserve cash, he said.

"With prices below $US60 the [Atlas] board will be talking about what do we do?"

"If the price fall is sustained and if falls towards $US50 per tonne, that should prompt people to shut mines. They would look to go on care and maintenance."

Auditors for Atlas warned last month the junior miner might have to sell assets or raise funds to repay debt if it fails to meet its latest cash flow forecasts.

Auditor KPMG said Atlas' cash flow forecasts were "highly dependent" on assumptions for the iron ore price, the Australian exchange rate and operating and capital costs.

"Should these key assumptions which underpin the cash flow forecasts not be achieved, the group may be required to source additional funds through debt or equity markets or a sell-down of assets," KPMG said.

Atlas Iron managing director Ken Brinsden could not be reached for comment.

Dollar a cushion

Veteran Perth dealmaker and Argonaut chairman Charles Fear said the current commodities downturn was the worst in more than 20 years.

"This is the deepest [downturn] I have seen since 1993," Mr Fear said. "Thermal coal took three years to halve [in price], iron ore took less than a year and oil has taken three months. Base metals are under enormous pressure."

The depreciation of the Australian dollar since December has cushioned the blow for the West Australian government and has helped relieve some of the pressure for many miners.

The West Australian government slashed its iron ore forecast for 2014-15 from $US122.7 a tonne to $US75 a tonne in December.

The iron ore price has averaged $US66.41 a tonne since December 3, when the government ruled off its books for its mid year forecasts.

The price fall has cut $481 million from expected iron ore royalty revenue. However, the softening dollar will boost the books by $426 million, meaning the net impact of the lower iron ore price is $55 million.

But the government is shouldering the burden by returning a chunk of royalty payments to junior miners when prices trade below $90 a tonne.

Eligible small miners are able to have half of their royalties reimbursed to them but must repay the state government by December, 2017.

Life support

One analyst who declined to be named said junior miners are operating on tenuous forms of life support.

"The danger in the Australian market is that you have a falling dollar meaning that the mid-tiers here are under the impression things will get better for them so they hang in there but for a correction in the price, which is good for the industry, we need them out," he said.

Rio Tinto is cutting about 800 employees and contractors as it hammers down costs.

A spokesman for Rio said the miner had been cutting costs for a number of years "in the knowledge of an expected decline in iron ore prices".

"We must continue to take actions that ensure our business remains competitive," the spokesman said.

"We have been identifying opportunities to simplify and streamline our organisation. Where possible, we are moving those affected into existing vacancies or other parts of our business. Unfortunately, in some circumstances there will be people leaving our business.

"We are working closely with our employees through this process. We will provide support and assistance to those who are impacted."