Corriente bullish on Mirador (August 12, 2004)

Independent metallurgical studies have confirmed positive results for the treatment of copper ore from the Mirador deposit in Ecuador.

Corriente Resources (CTQ-V) reports that tests on metallurgical composites indicate that need for a conventional copper-gold porphyry circuit. The circuit would use relatively coarse primary semi-autogenous grinding and ball-mill grinding to 140 microns, followed by copper rougher flotation and concentrate regrinding to 25 microns.

Studies show that a 30% copper concentrate can be produced at a recovery of 90%. There are no deleterious elements in the ore, and its hardness is average to moderately low.

“Our early expectation that the Mirador orebody was a simple chalcopyrite porphyry with coarse-grained characteristics and low variability has been confirmed,” says Ronald Simkus, Corriente’s senior vice-president of mining. “Clean copper concentrates will be easily marketed to smelters via our port facility at Puerto Bolivar.”

Copper is hosted dominantly as primary chalcopyrite, with minor amounts of secondary copper mineralization, occurring mainly as a shallow 0-to-20-metre-thick chalcocite blanket overlying the primary sulphide ore. Pyrite occurs widely throughout the deposit but at relatively low levels.

The pyrite-to-chalcopyrite ratio of 3:1 is in the lowest quartile for the industry. The pyrite is also coarse, averaging 98 microns, and this translates into a relatively clean concentrate. Additional minerals in the concentrate include predominantly quartz, feldspars and micas (total 95%) with minor clay and carbonate (total 3%).

Corriente is now working on a bankable feasibility study for an open pit and 20,000-tonne-per-day concentrator. The metallurgical portion of the Mirador feasibility study is being managed by AMEC Americas.

The metallurgical tests were carried out by SGS Lakefield Research under the direction of AMEC staff.

Corriente controls more than 700 sq. km in the region, including the Mirador, San Carlos and Panantza deposits. Together, these host a geological resource of 560 million tonnes grading 0.81% copper plus gold and molybdenum credits.