The metallurgical process at the Jacobina Mine Complex uses a simple and efficient milling process. The process involves the following activities: grinding of the run of mine material into a pulp, leaching the pulp in a conventional cyanide leaching process and then gold extraction of the enriched solution in a Carbon-In-Pulp (CIP) circuit.
The run of mine (ROM) material is hauled by trucks from the mine to the crushing facility adjacent to the processing plant. The ROM is initially sized by a 50 x 80 cm opening grizzly / rock breaker system located at the top of the primary jaw crusher. The primary jaw crusher, which is fed by an 80 tonne hopper, is 1,200 mm x 900 mm in size and has a 350 tonne per hour throughput capacity.
The product from the jaw crusher, which is smaller than 200 mm, is fed into two storage silos. The material is then feed into semi autogenous grinding mills and is ground to a nominal size of 80 percent passing 200 mesh. The No.1 Mill has the dimensions of 3,658 mm x 6,706 mm and features a single 1,342 kW motor. The No.2 Mill is 4,572 mm x 9,144 mm in size and is equipped with two 1,342 kW motors.
The pulp from the grinding circuit is then pumped to the leaching tanks. The leaching circuit consists of four 9.5 m diameter x 10.25 m high mechanically
agitated leach tanks and twelve 212 m3 Pachucas. The leach residence time is 24 hours.
The pulp is then sent to the CIP circuit. The CIP circuit consists of six 5.6 m diameter x 7.8 m high, 180 m3 capacity mechanically agitated CIP tanks. The enriched carbon from the CIP circuit is removed and striped of its gold. From here, the pregnant solution is circulated through electrowinning cells and a doré gold is produced consisting of 96 percent gold and 3 percent silver.
The milling process is fully automated using modern Siemens instrumentation and automation technology for better process control.
Approximately 200 m3/hr of the 450 m3/hr make up water is reclaimed from the tailings pond. A new tailings dam will be completed in 2008 and a new pumping system was added to handle the increased throughput.
In 2006 the implementation of the expansion has begun with the installation of a cone crushing circuit which has increased plant capacity to 5,000 tonnes per day from the original 4,000 - 4,200 tonnes per day and reduced power consumption at the mills. As well, Yamana has begun engineering and mine planning to increase production to 6,500 tonnes per day by early 2008 and to 8,500 tonnes per day by the end of 2008.