Iamgold Corp. said it will post a $400 million US gain on its books for the recent sale of the company's stake in two mines in the West African country of Ghana.

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Iamgold stock chart.

The Toronto-based global miner said Thursday it will book the one-time gain on its financial report from the $667 million sale of the company's 18.9 per cent stake in the Tarkwa and Damang gold mines.

The deal with a South African company, Gold Fields Ltd., announced last week, is slated to close by the end of July.

In its first quarter, Iamgold said it generated gold production of 290,000 ounces at a cash cost of between  $570 and $580 per ounce.

The gold producer also said it had production of niobium — a specialty metal used in steel alloys — of 1.1 million kilograms at a margin of between $15 and $17 a kilo.

President and CEO Steve Letwin said "our mines have had an excellent start in 2011."

"The performance of assets where we are the principal owner and operator has been impressive this quarter, specifically our largest assets, the Rosebel mine in Suriname and the Essakane mine in Burkina Faso."

Iamgold is a mid-tier gold mining company with attributable production of about one million ounces annually from eight gold mines, including current joint ventures and working interests, in West Africa, South America and Canada. It also operates Niobec, a niobium mine in Quebec.

Gold Fields is one of the world's largest unhedged producers of gold with annual production of 3.6 million gold equivalent ounces from eight operating mines in Australia, Ghana, Peru and South Africa.