The stock of Perth-based mining services group Mineral Resources fell 1.8 per cent in a flat sharemarket on Monday after the company's rating was lowered to "sector perform" from "outperform" by RBC Capital Markets and the bank ­lowered its profit forecast.

Although Mineral Resources, which owns iron ore mines in Western Australia as well as providing services to miners, was a "high quality" company, low iron ore prices had hurt investor sentiment, analyst Heath Andrews said.

"There seems to be a consensus view that iron pricing could remain under pressure for some time."

RBC estimates iron ore prices will be trading at about $US98 a tonne in fiscal 2015. Iron ore prices are currently sitting at about $US83 a tonne.

Sliding iron ore prices have raised concerns that other contractors, including NRW Holdings and Macmahon Holdings, which provides services to iron ore producer Fortescue Metals, are at risk of losing work from iron ore ­miners.

Leighton Holdings subsidiary Thiess is expected to lose about $11 million from unpaid work after Northern Territory-based iron ore ­producer Western Desert Resources went into receivership last week.

Thiess had a three-year mining ­services contract with Western Desert worth about $135 million.

Meanwhile, Perth-based mining services group Ausdrill said it was owed $8 million by Western Desert for drill and blast services, and was "not certain" whether it could recoup owed payments.

Falling prices have already forced the closure of several iron ore mines, including the Chinese-backed Cairn Hill mine in South Australia, and ­Territory Iron's Frances Creek mine.

Leighton, Downer EDI and NRW Holdings are among the ­contractors that are working on Gina Rinehart's Roy Hill mine, which plans to start shipping iron ore in ­September 2015 but could be forced to curtail production plans if prices ­continue to fall. About 28 per cent of Leighton's $7.7 billion Australian contract mining business stemmed from iron ore at June 30, according to the company.

Each of Grange Resources, which operates the Savage River mine in Tasmania, steel maker Arrium, with operations in South Australia, and Gindalbie Metals, which has half the Karara mine south-west of Geraldton in WA are also under scrutiny as analysts and investors assess the near-term prospects for their mining operations.

The highest-cost iron ore miner at present is believed to be Gindalbie Metal's 48 per cent owned Karara Mining, which is developing a mine near Geraldton in Western Australia's south-west. According to UBS, Gindalbie's Karara mine has an all-in production cost of about $US100 a tonne, with Grange at $US88 a tonne and Atlas Iron $US85 a tonne.

But for some producers, contractual commitments combined with financing pressures may leave them with little choice but to continue mining at maximum levels, even if they are losing money, which is similar to the situation of many local coal exporters.

The appointment of receivers to Western Desert came as monthly iron ore volumes shipped through Port Headland hit new records in August, of 37.4 million tonnes, which is a rise of 38 per cent year on year.

"There is the potential for further price pressures to come over the next few months," one Melbourne-based analyst said. In part, this reflects the seasonal nature of Chinese demand, which is routinely stronger from around November.

"Prices at these levels are pretty much unsustainable," Contango Microcap portfolio manager Bill Laister said. "Are we going to buy iron ore names at these levels? Probably not.

"Iron ore would be close to bottoming at these levels. I don't think it will bounce a lot; $US90-100 a tonne is where it should settle."

Production at second-tier iron ore miners such as Arrium, BC Iron and Atlas Iron is already running at maximum capacity, which is forcing them to look at ways of cutting costs. Arrium is estimated to have an all-in production cost of about $US89 a tonne.

"Arrium is now paying for the privilege of mining for practice from the short-life Peculiar Knob operation," Credit Suisse told clients in a research note.

Gindalbie's shares are holding near all-time lows.

"Gindalbie's got corporate structure issues with Ansteel, which is clouding its prospects," one analyst said, who did not wish to be named.

Despite its issues with an exposure to Karara Mining which has both production and cost problems, Gindablie managed to seal a $US400 million loan from two Chinese banks in late August, of which it has already drawn $US100 million, signalling their support for the mine for the time being at least.

Grange also wrote $200 million off the value of its Savage River mine due to the weak iron ore price, which tipped it into the red in the June half, although it has about $110 million in cash sitting in its balance sheet and negligible debt.

Other second-tier producers such as Atlas and BC Iron have large amounts of cash holdings, which give them some protection in the present shake-out, one analyst said who did not wish to be named.

Cape Lambert Resources chairman Tony Sage said he believed the iron ore price would settle at about $100 to $125 a tonne.

"If you haven't got your existing infrastructure in play, it makes things very difficult. BHP and Rio will kill it for a long long time; the price needs to drop below 60 in order to bother them. But companies in the seventies and eighties that can't reduce their costs and get extra tonnes out are really going to hurt. Companies that are suffering from infrastructure bottlenecks and can't get a product to port, for example, are going to be in trouble."