Aguablanca finally makes the grade

At long last, engineering and construction contractor Fluor has commissioned the processing plant at Rio Narcea Gold Mines‘ (RNG-T, RNO-X) Aguablanca nickel-copper mine, 90 km north of Seville, in southern Spain.

The long-awaited milestone was reached after a series of tests in January and February. The mill achieved its design rate of 195 tonnes per hour (1.5 million tonnes per year), with an availability rate of 94% during a pair of 5-day performance tests. Nickel recovery was around 75% (or 92% of the design rate of 82%) to yield a bulk concentrate running 13% combined nickel and copper.

A longer, 30-day reliability test saw slightly lower throughput of 185.25 tonnes an hour as availability fell to 89.3%. Nickel recovery came in at around 72%, or 87.4% of the design rate of 82%, and yielded a bulk concentrate grading 12.35% combined nickel and copper.

In January, nickel and copper concentrate grades of 7.17% and 7.01%, respectively, were achieved.

Fluor had struggled to get the plant running at a minimum of 90% of design — something it needed to do before it could turn the plant over to Rio. Rio is now focusing its efforts on expanding the plant to its final throughput rate of 235 tonnes per hour (1.8 million tonnes per year).

The open-pit and underground mine is designed for annual production of 18 million lbs. nickel, 14 million lbs. copper and 20,000 oz. platinum group elements (PGE) over 10.5 years. At the end of 2004, proven and probable open-pit reserves totalled 15.7 million tonnes grading 0.66% nickel, 0.46% copper and 0.47 gram PGE, based on a cutoff grade of 0.25% nickel.

Based on limited drilling, Rio figures underground mining could produce an additional 200,000-300,000 tonnes of ore later this year.

During 2005, Aguablanca milled 997,244 tonnes of ore grading 0.76% nickel and 0.55% copper to produce 11.9 million lbs. nickel and 10.8 million lbs. copper; recovery rates were 71.3% and 88.7%, respectively. The mine produced its first nickel concentrate during commissioning in late 2004.

Commissioning at Aguablanca was originally scheduled to wrap up during the second quarter of 2004, with a production startup anticipated by mid-2004. That timetable suffered as Fluor worked out some bottlenecks in the flotation circuit and made modifications to the semi-autogenous grinding mill, including the installation of new discharge grates and liners. The project also suffered a 3-week delay in obtaining a permit for construction of an 18-km high-voltage power line.

Rio previously said it was evaluating its legal options “as a result of the design deficiencies of the Aguablanca plant and the remedial actions that have had to be taken.”

The company is in the midst of an underground infill-drill program, with holes being sunk form a recently completed, 2,700-metre decline designed to access mineralization beneath the currently planned Aguablanca pit bottom. Plans also call for regional surface drilling.