PERTH (miningweekly.com) – Copper miner Sandfire Resources on Wednesday reported a decline in copper production from its DeGrussa mine, in Western Australia, as it transitioned from an openpit to an underground operation.

Copper production from the concentrator increased by 46% during the quarter ended March, to 11 632 t, compared with the 7 962 t produced in the second quarter of 2013, while overall copper production was lower than the December quarter’s 13 683 t.

Sandfire attributed the lower quarterly production to the scheduled completion of the direct shipping ore (DSO) crushing campaign.

Mill throughput and recovery also continued to increase steadily during the quarter under review, with recoveries constrained in the short-term by the treatment of transitional openpit sulphide material, which is scheduled to continue until mid-2013, and the head-grade of the initial underground stopes being in the lower range of stoping grades.

Sandfire noted that underground mining would continue to progressively ramp-up, with current underground mining rates of around 100 000 t/m, delivering ore to the concentrator. Full production rates of around 125 000 t/m would likely be achieved by mid-year.

As the underground development and stoping progressed further, blending of ore from different mining fronts would minimise variation in the medium- to long term, the copper miner said, which would underpin the company’s target recovery of over 90%, and production at the upper end of monthly targets of 6 400 t/m, for its first three years of operation.

The ASX-listed Sandfire noted that further optimisation programmes in line with plant ramp-up were also continuing, and were expected to build on operating improvements achieved to date.

With the lower recoveries for transitional openpit ore and the lower initial head grades from the underground operation, Sandfire estimated that full-year production was likely to be around 65 000 t of copper and 44 000 oz of gold.

Concentrator production guidance for the full year had been maintained at 35 000 t of copper and 17 000 oz of gold.