The copper-gold sulphide mineralization found at the Candelaria Copper Mining Complex is generally referred to as iron oxide copper gold (IOCG) mineralization. The sulphide mineralization occurs in breccias, stockwork veinlets, disseminations in andesite, and as an internal tuff unit. There are also some localized controls to mineralization in the form of faults, breccias, veins, and foliation. Candelaria has become an exploration model for Andean-type IOCG deposits that display close relationships to the plutonic complexes and broadly coeval fault systems. Depending on lithology and the structural setting, the polymetallic sulphide mineralization can occur as veins, hydrothermal breccias, replacement mantos, and calcic skarns. The Candelaria IOCG system lies within the thermal aureole of the Lower Cretaceous magmatic arc plutonic suite in the Candelaria-Punta del Cobre district.

Chalcopyrite is the only primary copper sulphide present in the Santos mine. Additionally to copper mineralization, there are economic values of gold. Most frequent gangue minerals are pyrite, magnetite, actinolite, k-feldspar, chlorite, biotite and hematite.

In the Santos mine, three types of mineralized bodies are observed: veins, mantos, and breccia bodies. An important vein in the Santos mine is the Isabel, which is oriented northwest-striking, and extends over 1 kilometre in length and between 4 and 30 metres in width. Manto-type mineralization occurs as tabular bodies hosted in two sedimentary horizons located in the floor and roof of the albitophyre. The manto mineralization is characterized by variable iron contents with magnetite common in the north and deeper areas, and specular hematite in the south. Mineralization occurs within breccia bodies is typically contained with the albitoforo and lower andesite and is formed by steeply west-dipping and north-northwest- to northwest-striking bodies.

Mineralized bodies at the Alcaparrosa mine have a manto-type geometry that trend to the northeast and dip to the west. Ore and gangue mineralogy consists of chalcopyrite, pyrite, and magnetite, with trace pyrrhotite, molybdenite, and arsenopyrite.

Mineralization styles at the Alcaparrosa mine also occurs as veinlets defining dense stockwork, breccias (hydrothermal potassium feldspar and magnetite), as well as fine dissemination in biotite meta-andesites. High grade bodies are also found in massive veins striking north-northwest, north, and east.

Minera Ojos del Salado consists of the Santos and Alcaparrosa underground mines.

The Alcaparrosa mine currently produces 4,300 tonnes per day of ore and is expected to keep it as a steady state production rate. The life of mine average grade is 0.77 percent copper. The Santos mine will continue to produce at its current rate of production of 5,100 tonnes per day of ore with an average life of mine grade of 0.94 percent copper.

The three underground mines (Candelaria Underground, Santos, and Alcaparrosa) utilize a sublevel stoping mining method for ore extraction. This method is ideal for relatively large, vertical, as well as thick deposits with favourable and stable host rock. Stopes can typically be up to 100 metres high with sublevels at 20 to 60 metre intervals. The length of the stopes is generally 20 to 80 metres with widths varying between 20 to 30 metres. Stopes are drilled down from the sublevel drilling drifts as benches using 4.5 inch diameter downthe-hole holes. The holes are loaded and blasted in vertical slices towards an open face. The blasted ore gravitates to the bottom of the stope and is collected through drawpoints at the production level below. Ore is mucked from the drawpoints using surface type front-end loaders and load haul dumps. The mucked ore is dumped into 30-tonne highway type trucks and hauled up the ramp to a surface stockpile for subsequent rehandling and processing.

Minera Candelaria (for the Alcaparrosa underground mine)
Run-of-mine ore is trucked to a primary gyratory crusher. The crushed product is transported using an overland conveyor belt to a coarse ore stockpile with a combined live and dead capacity of 500,000 tonnes. Semi-autogenous grinding (SAG) mills are followed by pebble crushing, with separate grinding of a portion of the crushed pebbles and the remainder brought back to the SAG mills. This circuit is followed by closed-circuit ball milling with hydrocyclones to classify the flotation feed size.

Minera Ojos del Salado
The concentrator flowsheet comprises a closed-circuit crushing plant including a primary jaw crusher (48 by 60 inches), a secondary cone crusher and two tertiary cone crushers.

The grinding plant has three ball mills (one 9 by 9 feet and two 10.5 by 13 feet) operating in parallel and in closed-circuit with hydrocyclones.

Minera Ojos del Salado PAC Plant
The PAC concentrator of Minera Ojos del Salado has been in operation since 1929. The concentrator processes 3,800 tonnes per day of fresh feed from the Santos underground mine with an historical average head grade of 0.85 percent copper with a copper recovery of 94 percent. Copper concentrate produced has averaged 30 percent copper, 5 g/t gold, and 67 g/t silver since 2004. Gold and silver recoveries are slightly lower than Candelaria, at 72 percent each.

The flotation plant uses multi-stage, mechanical (self-aspirated and forced-air) flotation cells varying in size from 100 to 1500 cubic feet. After rougher flotation, regrind milling and column cells are used to generate a final concentrate which is thickened and filtered using a 30-square- metre ceramic disc filter. Final flotation tailings from the PAC plant are pumped to the main Minera Candelaria tailings storage facility but not processed through the magnetite recovery plant.