The problem was that IAMGOLD's feasibility study showed it was NOT feasible to mine their deposit using lower cost open pit mining methods... which was what they'd hoped spending the $$$ doing the work on the feasibility study would show. Instead, the work they did showed some they have some higher grade materials in much narrower zones at depth... but, the lower grade materials were much lower grades, and together they didn't average out well enough, with the higher grades in narrower intersections, to justify open pit mining.
The difference... first, is that Nemegosenda has larger intersections, with higher grades in the lower grade ores, resulting in better AVERAGE grades overall, and with those better average mineral values beginning right at and near surface, open pit mining is practical. IAMGOLD's ore surface is a couple hundred meters deep... meaning they'd have to pay to dig a really deep hole... a big cost imposed even before getting to the first rock containing ore.
Basically, looking at the original work done by Gulf Dominion... it appears to show that most of the known historic resource in the Hawke Zone at Nemegosenda would be mined out... before the hole being dug doing that got as deep as the one IAMGOLD would have to dig just to reach their first ore...
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