Nevsun Resources Ltd. said Oct. 4 that its Bisha zinc-copper-gold mine in Eritrea declared commercial production for its zinc expansion, effective Oct. 1 with the successful commissioning of a new zinc flotation plant.

Since commissioning began in June, the existing copper circuit and the new zinc circuit produced about 40,000 tonnes of commercially salable zinc concentrate.

The company noted that the Bisha mine made three ocean shipments of concentrate in September for sales totaling approximately US$21 million.

Nevsun's President Cliff Davis said the start of zinc concentrate production coincides with the recent rally in zinc prices in 2016, and a decline in spot treatment charges for zinc concentrates.

However, the concentrate produced from the copper circuit is currently considered "bulk con," which is not of a quality that is normally accepted as a copper concentrate by most copper smelters.

The company has tapped external specialists to carry out test work to resolve the issue, which results from complex mineralogy of portions of the primary ore mined from the Bisha main pit, and has prevented successful clean separation of the copper and zinc ores on a consistent basis.

The ongoing test work is expected to be completed by the end of 2016.