Article on how & why Bisie mine is lowest cost producerhttps://www.canadianminingjournal.com/news/case-study-gekko-ipj-boosts-efficiency-at-bisie-tin-mine-in-congo/
Not only is this the highest grade tin deposit in the world by far, but production costs have been reduced since built.
Interesting couple of points here:
1) fine tuning has increased production above design and cost
2) reference to THREE phases of Bise develpment with the first as Mpama North and second as Mpama South