The Constancia deposit is a porphyry copper-molybdenum system which includes copper-bearing skarn mineralisation. Multiple phases of monzonite and monzonite porphyry have intruded a sequence of sandstones, mudstones and micritic limestone of Cretaceous age.

The majority of the mineralisation is associated with potassic alteration and quartz veining, occurring as chalcopyrite-(bornite)-molybdenite pyrite mineralisation in “A” and “B” type veinlets, and also replacing ferromagnesian minerals or filling fractures. Copper grades typically vary from 0.2% up to 4%, and are highest where fracture-filling style copper mineralisation is superimposed on earlier disseminated copper mineralisation. The high grade hypogene copper mineralisation is hosted by a dense A-veinlet stockwork developed in an early porphyry phase.

Pyrite/chalcopyrite ratio is typically low, being in the order of 1:1 to 2:1. Molybdenite commonly increases with depth, related to “B” veinlets. Bornite occurs sporadically especially at deeper levels, sometimes associated with some gold values.

Propylitic alteration is peripheral to the potassic alteration and extends more than one kilometre from the porphyry intrusive contacts. The propylitic alteration mineral assemblage includes epidote-chlorite-calcitepyrite rhodochrosite. Subordinate chalcopyrite is also present, filling fractures or replacing mafic minerals. Sphalerite-galena veinlets and veins are distributed as a halo to the copper molybdenum mineralisation within the propylitic alteration halo, occurring at distances of up to 3 km away from the porphyry copper system.

Phyllic alteration forms a pervasive carapace surrounding and sometimes overprinting potassic alteration. The phyllic alteration accompanies almost complete destruction of primary rock textures; the mineral assemblage includes sericite-quartz-pyrite, limited amounts of chalcopyrite and associated occasional “D” veins and veinlets.

At the contact between the intrusives and limestones, magnetite ± garnet skarn develops, while a pyroxene–diopside (garnet–epidote) association is more common in calcareous sandstones and arkoses of the Chilloroya formation. Skarn mineralisation is volumetrically much smaller, but grades are normally higher.

The Constancia project is a traditional open pit shovel/truck operation with two deposits, Constancia and Pampacancha. The project consists of open pit mining and flotation of sulphide minerals to produce commercial grade concentrates of copper and molybdenum. Silver and a small quantity of payable gold will report to the copper concentrate. The Pampacancha deposit, located 5 Km SE from Constancia, exhibits higher grades of copper and gold and is scheduled to enter into production during 2016.

The Constancia ultimate pit will measure approximately 1.7 km east to west, 1.5 km north to south, and have a maximum depth of approximately 600 m. The Pampacancha ultimate pit will measure approximately 0.6 km east to west, 1 km north to south, and have a maximum depth of approximately 300 m. There is one primary waste rock facility (WRF), which is located to the south of the Constancia pit and is intended to be used for both deposits. The processing facility is located approximately 1 km west of the Constancia pit, while the tailings management facility (TMF) is located approximately 3.5 km southwest of the Constancia pit.

The primary crusher, belt conveyors, thickeners, tanks, pebble crushers, flotation cells, ball mills and various other types of equipment will be located outdoors without buildings or enclosures. To facilitate the appropriate level of operation and maintenance, the filters and concentrate storage will be housed in clad structural steel buildings.

The crushing circuit consists of a 60” x 113” gyratory crusher, a variable speed belt feeder and a coarse ore stockpile feed conveyor.

The grinding circuit requires two SAG mill feed conveyors. Dual reclaim chambers will be used to house four apron feeders that will draw ore from the crushed ore stockpile to the SAG mill feed conveyors.

The grinding circuit consists of two identical trains of grinding; each train consists of a single semiautogenous grinding (SAG) mill and a ball mill. After year three of production there will be a pebble crusher added to each line. The ball mills are operated in closed circuit with a cyclone cluster to produce cyclone overflow which reports to rougher flotation feed.

The tailings from the molybdenum flotation roughers and molybdenum cleaner scavengers report to a copper concentrate thickener. The thickener underflow is removed and stored in two surge tanks. The filter feed is pumped to two Larox horizontal filters. The filters produce a filter cake of 9% moisture. The filter cake is dropped to ground and is transferred to temporary storage by front end loader. Filtrate, cloth wash, and flushing water are returned to the copper concentrate thickener.