News Out - We Probably Dodged A BulletThe comments about the ongoing metallurgy tests indicate that manganese is indeed the problem; my reading suggests it is usually the higher oxides of manganese.
I was encouraged by the comment that the native silver, and silver halides are amenable to cyanidation. But we just don't know the content of manganese oxides at this point. Again from my reading, manganese is a probably better problem to have than silica encapsulation, because it seems to be fixable with acid, rather than with expensive ultra-fine grinding.
One patent suggests a simultaneous leach for both manganese and silver using cyanide and acid. Acid is what is meant by "reduction"; the PH is reduced. But this better be at atmospheric prerssure and not High Pressure Acid Leaching ("HPAL") in an autoclave, like the Sherritt disaster, ongoing at Ambatovy.