Apex Begins Silver Concentrate Production at San Cristobal


Following the start of commissioning at its San Cristobal silver mine in southwestern Bolivia,
shown here during construction, Apex Silver said in early August that it had achieved continuous
mill throughput of 19,000 mt/d---within 5% of design capacity.
Apex Silver Mines announced on August 7 that production of silver-bearing concentrates at the San Cristobal zinc, lead and silver mine in southwestern Bolivia had begun. According to the company, the plant reached mechanical completion in late June 2007 and began start-up commissioning in early July. The first rail shipments from the plant were expected to take place a week after the August 7 announcement.

Apex Silver said that, as of July 31, more than 3.5 million million mt of ore had been stockpiled for the concentrator. The primary crusher and overland conveyor were operating at design rates delivering ore to the coarse ore stockpile. With production testing ongoing and operating with a previously untrained workforce, the plant was operating with the semi-autogenous mill (SAG) and one of two ball mills. In processing the harder of the two ore types in the San Cristobal ore body, the company said it had achieved continuous throughput of 19,000 mt/d, within 5% of design capacity. The motor for the second ball mill had been repaired and is being commissioned, and Apex expects continuous production from that ball mill in early September.

Apex said the flotation circuit had been commissioned and the mine is producing both silver-bearing lead and zinc concentrates. The filtration and load out system also had been commissioned and concentrate containers were being loaded for rail transport to the port at Mejillones, Chile. According to the company, all other systems including the well field, tailing system, railroad, and other supporting systems have been commissioned and are generally performing as anticipated.

The plant was scheduled to continue in startup and commissioning mode during August with emphasis on commissioning of the zinc regrind circuit and fine tuning throughout the flotation plant including improvements in the calibration of instruments and tuning of control loops and level controls in the plant.