An Open Letter To Angry GeologistDear Angry Geologist,
I suspect that you have missed the boat badly with your nonsensical conjecture about fine-grained, disseminated silver at Sandra-Escobar. Likewise, your use of Athena Langtry as an analog was also an extremely poor choice.
A review of the literature quickly reveals 3 main problems that can impede silver recovery in cyanidation.
1.) Silica encapsulation of silver grains;
2.) The presence of oxides of manganese;
3.) Large, yes I said large silver grain sizes that increase leach times.
Both Langtry and La Pitarrilla are sediment-hosted deposits, while the oxide zone at Sandra is found in extrusive volcanics (rhyolite). Your mistake was in confusing the different metallurgical difficulties typically found in these entirely different depositional environments.
If you had bothered to properly do your homework, it would have been clear to you that it is, in fact, common in Mexico to have manganese oxides in near surface deposits and that these difficulties are routinely handled with well-establish pre-treatment circuits. The earliest paper I found on this is dated 1925. Enen your own reference, 911Metallurgist has an extensive section on rhyolite and manganese, which you obviously did not bother to read.
Next time, try harder to get things right, before you bother posting any more or your nonsense.