TORONTO (miningweekly.com) – Canadian base metals miner Capstone Mining on Thursday reported third-quarter production results that were below analyst expectations, placing its full-year output guidance at risk.

The combined output from its two copper mines totalled 18.9-million pounds, dragged down by weaker production from Minto, in Canada's Yukon Territory. The production results excluded that of the Pinto Valley, which, in April, Capstone announced it would buy for $650-million from global miner BHP Billiton in a deal expected to close on Friday.

Capstone produced 7.3-million pounds of copper in concentrate at the Minto mine, which suffered from lower grades at 1% copper, which were partially offset by increased throughput of 360 000 t and in-line copper recoveries at 92.2%

Its Cozamin operation, in Mexico, produced 11.6-million pounds of copper in concentrate, boosted by higher grades of 1.96%.

The average total copper cash costs totalled $2.14/lb at Cozamin and $1.20/lb at Minto and an average total cash cost of $1.57/lb.

By-product production during the third quarter included 4.5-million pounds of zinc, 400 000 lbs of lead, 465 000 oz of silver and 2 894 oz of gold in concentrates.

Capstone reiterated its 2013 production and cost guidance of 85-million pounds of copper at a total operating cash cost ranging from $1.65/lb to $1.75/lb. However, Laurentian Bank Securities metals and mining analyst Christopher Chang said that given year-to-date production of only 56.9-million pounds of copper, representing 67% of the target, he believed the company would likely miss its organic production guidance for the year, excluding Pinto Valley production.

The Pinto Valley acquisition is expected to catapult the company into the mid-tier of global copper miners by adding 130-million to 150-million pounds to its production total.

The company’s TSX-listed shares traded in significant volumes on Thursday, and in the early afternoon changed hands at C$2.55 apiece, having gained C$0.05.