TORONTO (miningweekly.com) – Vancouver-based base metals producer Capstone Mining this week reported slightly weaker quarter-on-quarter output, as adverse weather and lower grades at its three mines impacted on its performance.

The TSX-listed company, with mines in Canada, the US and Mexico, on Tuesday reported consolidated output of 26 200 t of copper for the three months ended September 30 and 81 500 t of copper in concentrate and cathode in the year-to-date periods, with additional by-products of zinc, molybdenum, lead, silver and gold.

The quarter’s output was 5.7% lower than the pervious quarter’s 27 700 t.

Payable copper shipped for the quarter from all three mines was 29 031 t.

At Pinto Valley, in Arizona, recoveries continued strongly in the period, more than offsetting marginally lower throughput than planned. Grade was as expected for the quarter. The mill posted its highest average quarterly throughput to date and had continued to demonstrate consistent improvement, averaging just under expected rates for the third quarter.

Heavy rains in September caused some wet ore to slow the crushing circuit.

At Cozamin, in Mexico, throughput and recoveries were good, partially offsetting lower-than-planned copper grades. The copper grade improved in September, slightly later than called for in the 2014 mine plan, as the installation of additional ground support impacted the release of some new mining areas.

At Minto, in Canada, throughput and recoveries continued as planned. Grade was slightly lower than planned as more stockpile was milled than originally planned to improve the efficiency of throughput. The Area 118 openpit mining was completed in September and the M-Zone underground was expected to be complete this month.

Processing in the fourth quarter would be from stockpile, supplemented with ore from the M-Zone along with Area 118 underground, which had been brought forward in the mine plan, owing to a delay in receiving the Yukon Water Board’s water-use licence amendment, which was required to start prestripping of Capstone's Minto North pit.

Capstone's full-year guidance for 102 000 t of copper in concentrate, at a C1 cash cost of $1.90/lb to $2/lb of payable copper, net of by-product credits and selling costs, remained unchanged.

The company’s TSX-listed stock had lost almost 30% in value since the start of the year and was down C$0.03 a share at C$0.09 apiece on Wednesday.