MVC produced 13.3 million pounds of copper at a cash cost of US$1.97/pound, and 0.2 million pounds of molybdenum, in the June quarter. The results were below forecast "as a result of continued low plant recoveries during the quarter".

"In Q2-2019, as required by the mining plan sequence, Cauquenes material was still being extracted from the same low quality, high fines extraction zone that also affected Q1-2019 production," Amerigo reported this week.

"Production in Q3-2019 is ramping up following completion of the new Cauquenes extraction sump."

Henderson said MVC was extracting better quality material from Cauquenes, with the 48m-deep extraction sump completed and operational early this month. The sump had enabled MVC to regain access to coarser material with better recoveries, lifting copper production from about 150,000lb/day to 180,000lb/day.

Production was expected to continue to ramp up as hydraulic monitors in Cauquenes progressed toward deeper, higher grade material.

MVC has also installed and is operating its new regrind mill, completing the US$30 million Cauquenes Phase II expansion that was expected to take annual copper output to 85-90Mlbpa at cash costs of $1.40-1.60/lb.