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 mine is a traditional open pit operation using conventional truck and shovel mining. The Constancia ultimate pit design will measure approximately 1.8 km east to west, 1.6 km north to south, and have a maximum depth of approximately 660 m. The Pampacancha ultimate pit design will measure approximately 0.6 km east to west, 1 km north to south, and have a maximum depth of approximately 300 m. A primary waste rock facility (WRF), which is located to the south and east of the Constancia pit, is intended to be used for both deposits.

The processing facility is located approximately 1 km west of the Constancia Pit. A non-acid generating (NAG) stockpile for waste material is located at the south side while the tailings management facility (TMF) is located 3.5 km to the southwest of the Constancia pit.

Final pit limit designs have been created for Constancia and Pampacancha based on the selected pit shells from the pit optimization. Nine pit stages were developed for Constancia and two pit stages for Pampacancha Pit. The minimum mining width for each phase is 60 metres which allows for operation of a shovel, trucks (in two lines) and a drill. The phased development strategy consists of extracting the highest metal grades along with minimum strip ratios during the initial years to maximize the economic benefits of the ore-body, while enabling smooth transitions in waste stripping throughout the life of the mine to ensure enough ore exposure for mill feed.

The Process Plant was designed, built and commissioned by Ausenco. the concentrator throughput capacity is 90 ktpd with a 94% physical availability. The Constancia Process Plant consists of the following areas: crushing, stockpiling, milling, flotation (rougher and cleaner), regrind, thickening, filtration, tailings and the molybdenum processing plant. Final products are copper and molybdenum concentrates which are sent via road from site to the port of Matarani for shipment to customers.

Power supply is provided by the south national energy system in the highland sector (New Tintaya sub-station). Water for the process plant is provided by recirculation from the tailings management facility (TMF), process water from thickening, and dewatering wells from the mine (fresh water).

For concentrator plant control, a DCS system is used for starting and stopping equipment, level monitoring, lubrication systems, flows, temperature, equipment protection alerts, among others.