The ore at San Bartolomé is mined using conventional load and haul surface mining techniques without the need for drilling and blasting. There are two types of ore being mined and processed: whole ore and screened ore.
Whole ore is processed by conventional crushing and grinding using a SAG/ball mill combination and cyanide leaching in a counter-current decantation (CCD) circuit followed by silver recovery using a Merrill-Crowe process. The screened ore is mined from the lower flanks of Cerro Rico and is screened into +8 mesh and -8 mesh fractions for processing and for pumping to the tailings dam, respectively. The +8 mesh fraction is milled and processed using the same process flow as the whole ore. Product from the Merrill-Crowe circuit is smelted on site to produce a doré which is shipped to market.
View the latest Technical Report for the San Bartolomé mine.
Geology and Exploration Potential
San Bartolomé has been extensively explored by pits and trenches. Current exploration is being conducted to define and enlarge the known surface silver-bearing deposits and to discover additional deposits near Cerro Rico and the ore processing facility at San Bartolomé.
The operation exploits mineral reserves from four deposits located on the flanks of Cerro Rico and the surrounding areas near Potosí. These deposits are known as Huacajchi, Santa Rita, Diablo Este and Diablo Norte. These alluvial and colluvial deposits were formed by the erosion of disseminated mineralization in the upper portions of Cerro Rico.
The silver mineralization at San Bartolomé is hosted in unconsolidated sediments (pallacos), reworked sediments (sucus and troceras) and oxide stockpiles (desmontes) from historic mining that occurred on the flanks of Cerro Rico. Silver, along with tin and base metals, is located in multiple veins, veinlets and stockworks that occur in a northeast trending belt which transects Cerro Rico. The upper parts of the Cerro Rico mineralized system were subsequently eroded and re-deposited into the flanking gravel deposits. Silver is hosted in all portions of the pallacos, sucus and troceras with the best grades segregated to the coarser-grained silicified fragments. These deposits lend themselves to simple, free digging, surface mining techniques and can be extracted without drilling and blasting.