Ann: Exceptional Phase 1 Ore Sorting Results from Korbel Main, page-55

Heap leach is very cheap for low grade processing.

If they do grade control drilling they have better understanding of grade of each block of ore as it is mined.

Based on the results of grade control drilling, they would decide which blocks of crushed ore to:

1. Move direct to heap leach pad
2. Bulk sort and move to heap leach pad ( ore at margin of cutoff grade )
3. Bulk sort and then run through further crushing for particle sorting and traditional milling ( ultimately run through grinding circuit and then tank leaching )

For #1 ... if heap leach effectively recovers gold without intermediate sorting no point in extra OPEX $$$ to run the sorter

It becomes a cost trade-off decision. Working out a flow sheet that trades off total recovery with total OPEX.

Also. A possible scenario here is pre-strip material and some waste becomes profitable. Many heap leach mines are 1:1 strip ratio (waste : ore ). Maybe they can pull strip ratio down to 0.9:1 or even 0.8:1.