Geology and Metallurgy
The Shafter deposit is the northeastern, down-dip extension of the previously mined Presidio mine workings and has been divided along its east-west trend into five exploration sectors or blocks. Silver mineralization at Shafter and the historical Presidio mine is hosted by the Mina Grande Formation limestone over an approximate three mile length. It is classified as a carbonate replacement deposit (CRD) and is similar to many of the world's largest CRDs which occur in adjacent northern Mexico.
Considerable test work done by previous operators indicates the highest recoveries for silver will be by in-tank leaching followed by production of a silver doré using the Merrill Crowe process. Historical silver recoveries at the Presidio mine were 86% to 87% and are expected to be similar at Shafter.