Timmins Gold has begun drifting into underground veins parallel to the south wall of its San Francisco open-pit mine in north-central Sonora, Mexico. The drift is part of a pilot program to test mining and processing of underground ore in preparation for full-scale underground mining.
Drilling has delineated three mineralized veins near the south wall of the San Francisco pit, with average widths of about 4 m and grades ranging between 2.5 and 5 g/mt gold. The veins are located within 50 to 100 m of the current south pit wall. Veins extending along 300 m of strike and 200 m of dip have been delineated to date.
The pilot mining program involves drifting 90 m into the south wall of the pit to access the veins, followed by 200 m of lateral drifting to extract 14,000 mt of ore. The program is designed to test ground conditions, mining costs, grade, and metallurgical recovery of the underground ore.
The drifts will also provide efficient platforms for further underground in-fill and exploration drilling.
Timmins Gold plans to process ore recovered from the pilot phase through selective fine crushing and heap leaching. The effect of crush size and heap leach parameters on the metallurgical recovery of the underground ore will be investigated. Timmins Gold estimates the pilot program will take three to four months to complete.
The San Francisco open-pit, heap-leach operations produced 120,023 oz of gold and 85,262 oz of silver in 2014. In-pit proven and probable reserves at year-end 2014 were estimated at 71.4 million mt grading 0.56 g/mt gold and containing 1.27 million oz of gold.
Timmins Gold is a Canadian company headquartered in Vancouver, Canada.