Shares in Atlas Iron slumped more than 5 per cent after the mid-tier Pilbara iron ore miner posted a first-half loss of $256 million on its recently announced non-cash writedown of $258 million.

Underlying profit after tax was just $1 million, compared to $62 million in the previous corresponding period, reflecting sharply lower iron ore prices in the period.

The result was achieved on revenue of $288.3 million, down 15.6 per cent on the previous period.

The company will not issue an interim dividend.

Atlas said its first-half result was hit by sharply lower iron ore prices, a stronger Australian dollar and reinvestment in the business.

Its bottom line loss was attributed largely to a $258 million non-cash impairment charge on capitalised tenement costs and a write down on non-core assets announced last week.

However Atlas said a very strong recovery in iron ore prices was now generating substantial margins, as illustrated by an unaudited cash surplus from operations of $32 million for the month of January.

"Atlas is now producing at a rate of 8mtpa and is on track to increase production to 10mtpa by the end of June 2013," the company said.

Cash and cash equivalents increased to $419.8 million at the end of the period.