Copper mineralization occurs as an intrusive-related deposit within the Contact batholith and is observed in quartz veins within structural zones and in the surrounding granodiorite. The copper content is highest in the quartz veins, particularly where chalcocite is present, but grades outward into granodiorite where copper minerals occur in quartz veinlets, fracture coatings and disseminations. Mineralization is in the form of tenorite, chrysocolla and cuprite, and lesser chalcocite and covellite. Oxidation is observed to depths of 2,000 feet in drilling.

Ore production will be by conventional open pit mining methods. The primary mining equipment selected consists of rotary blast hole drills, 19.5 cubic yard hydraulic shovels, and 150 ton haul trucks, supported by track dozers and other ancillary equipment. Drilling will be in 20-foot high benches, double benched with 25-foot wide catch benches on final slopes. Blasting will utilize ammonium nitrate-fuel oil (ANFO) supplemented with emulsion for explosives as most blast holes are expected to be dry. The ore will be hauled by trucks to the crushing area east of the pit, and then conveyed to the heap leach pad south of the pit. Material below the cut-off grade will be hauled by trucks to the waste rock storage facility north of the pit.

The open pit is designed and mined in three phases in order to maximize the grade during the initial years and to balance the required waste stripping over time. Mining in Phase 1 begins at the west end of the ultimate pit, between bench elevations 5,400 feet and 6,200 feet ASL, and progresses eastward to a final pit depth at elevation 4,940 feet ASL. When fully mined, the ultimate pit as planned extends 8,300 feet in length from west to east, and 2,800 feet in width from north to south.

Ore production is planned to vary up to 57,000 tons per day (18.9 million tons per year) in order to maintain a consistent copper production of 50 million pounds per year from the SX-EW plant. Total mine production of ore and waste will reach 226,000 tons per day (83 million tons) in year five. Mining will be on a seven day per week schedule, with two shifts per day.

The Contact Copper Project is designed as an open-pit, heap leach operation. Processing will begin with primary and secondary crushing, followed by stacking the ore on a heap leach pad. Copper will be leached by sulfuric acid solution and processed through a solvent extraction-electrowinning plant (SX-EW) to produce high-purity copper cathodes on site.

Ore will be reduced to a size of 100%-minus one inch using two-stage crushing operating in open-cycle. Ore from the mine will be hauled to the crushing area, located at the east end of the pit, where it will be dumped into a 300-ton hopper and apron feeder which will feed the primary gyratory crusher. From the primary crusher, the ore will be conveyed to a 40,000 ton coarse ore stockpile and withdrawn to secondary cone crushers and then conveyed to a 40,000 ton fine ore stockpile. From the fine ore stockpile, the ore will then be conveyed to the leach pad using a series of mobile conveyors and a radial stacker which will place the ore on the pad for leaching in 10 to 20-foot lifts. The crushing, conveying and stacking circuit is sized to a capacity of 60,000 tons per day.

Crushed ore, once stacked on the leach pad, will be leached with a weak sulfuric acid solution. The leach pad is located on the south side of the open pit on a side slope that drains towards the east and toward the processing plant (Figure 16-3). Solution will be distributed to the pad through piping and emitters at a nominal rate of 0.005 gpm per square foot of surface area, and recovered from the leach pad through a system of drains which direct the solutions to a collection pond at a design rate of 7,000 gpm. Four ponds are required to support the leaching operations.

The solvent extraction circuit will consist of two parallel sets of cells, each with two extraction cells in series or parallel followed by stripping cell. In the circuit, the PLS flows counter-current through the extraction stages where it is contacted with an organic solvent in mixer-settler tanks. Hydrogen ions in the organic exchange with copper ions in the PLS to produce a copper-loaded organic and raffinate. The organic is immiscible in the raffinate and is separated by flowing over weirs at the ends of the settler tanks. Once stripped of copper, the raffinate flows to the raffinate pond and then on to the ILS pond where fresh acid is added before pumping to the heap leach pad. The copper-loaded organic is pumped to the stripping cells where the organic is stripped of copper by strong sulfuric acid and recycled back to the extraction cells. The acid solution leaving the stripping cells is filtered and pumped to the tankhouse where the copper is plated on stainless steel cathodes in electrowinning cells. The cathodes are removed from the cells every seven to nine days by overhead crane and the plated copper is stripped from the cathodes by machine and bundled for shipping.