The company reported an initial inferred resource of 97 million tonnes grading 1.02gpt for 3.2 million ounces gold.
Iamgold has increased its interest in the Nelligan joint venture with junior Vanstar Mining Resources from 24% to 75% after making its last cash payment of C$2.35 million.
Craig MacDougall, Iamgold's SVP of exploration, said the move underscored Iamgold's view "of the favourable exploration potential for the discovery of additional resources".
"We look forward to continuing to work with Vanstar as we advance our exploration efforts on the project," he said.
Iamgold can increase its stake to 80% by delivering a feasibility study.
"It is reassuring to see that our partner completes all the requirements more than two years before the deadline set in the agreement. This confirms well the great potential of the Nelligan project," said Vanstar CEO Guy Morissette.
JV operator Iamgold said next steps included further metallurgical test work to help optimise recoveries and the flow sheet.
Planning is also underway for more drilling including infill, extension drilling at depth, and step-out targeting along strike. The company will also undertake prospecting on several high-priority regional targets.
Iamgold shares (TSX:IMG) gained more than 2%, or C10c, on Wednesday to $4.57 taking 12-month gains to 5%. The company has a market capitalisation of $2.1 billion (US$1.6 billion).