One of the largest input cost for mine is energy. Grinding ore...

One of the largest input cost for mine is energy. Grinding ore is energy intensive. The smaller you grind, the more energy intensive. Look at the Bibiani feasibility study you reference. Power is half of all processing ($10/$20 per tonne). Recovering another 40% of the gold would only contribute another 5% or so of revenue whereas the re-grinding and leaching would contribute over 10% to operating costs. Too, most of the higher grade gold is found at depth and later in mine life, anyway. So why pay up front capital to maximize gold recovery when capex for gold recovery only pays for itself later in mine life? Doesn't make much sense to me.