Mineralization at Copper Mountain is classified as an alkalic porphyry deposit. Although there are several areas that have been mined separately over time, both alteration and lower-grade mineralization occurs between these areas, and all mineralization is thought to be part of a large, single system.

As a generalization, mineralization at Copper Mountain consists of structurally controlled, multidirectional veins and vein stockworks, with peripheral disseminations. Mineralization had been subdivided into four types, as follows: 1) disseminated and stockwork chalcopyrite, bornite, chalcocite, and pyrite in altered Nicola and LHIC rocks; 2) hematite-magnetite-chalcopyrite replacements and/or veins; 3) bornite-chalcopyrite associated with pegmatite-like veins (coarse masses of orthoclase, calcite, and biotite); and 4) chalcopyrite-bearing magnetite breccias. Each mineralization type can be found in all pit areas, but each pit is unique with respect to the relative quantities and character of mineralization type.

Both mineralization and alteration demonstrate a zonation through the camp, though not in a manner typically associated with calc-alkaline porphyry deposits. Three main types of alteration have been defined—hornfels, sodic, and potassic; each has its own spatial and temporal distribution.

Sodic alteration is commonly pervasive (sodic metasomatism), but can also occur as fracture- controlled veins or vein-stockworks. Pervasive sodic alteration occurs as a texturally destructive albite-diopsideepidote metasomatism. In addition to albitization of feldspars and conversion of ferro-magnesium minerals to epidote (± diopside and chlorite), magnetite and opaque minerals are destroyed. This process results in bleaching of the original rock and a reduction in grain size, forming a pale-gray or greenish-gray, very competent rock. A wide band of intense sodic- metasomatism cuts across the mine area in a northwest–southeast direction, extending from the north side of the Ingerbelle deposit and across the Similkameen River canyon, through the south side of Pit 2 and the north sides of Pit 1 and Pit 3. Much of the sodic alteration appears to be early and pre-mineralization; however, there also appears to be a more confined, later phase of sodic alteration with a high pyrite-tochalcopyrite ratio that occurs on the northern and southeastern sides of Pit 1, which may be associated with small cylindrical intrusions.

Potassic alteration occurs as veins and fracture fill (K-feldspar and biotite), or as pervasive K-feldspar flooding of the rock matrix. Where potassic alteration overprints the sodic alteration, it is almost exclusively as fracture fill and veins. In areas peripheral to the sodic alteration, potassic alteration is pervasive, either flooding the rock matrix with fine-grained potassium feldspar or replacing primary plagioclase with potassium feldspar, and ferro-magnesium minerals with biotite, epidote, calcite, chlorite, and magnetite. Potassium alteration typically produces rocks with a faint to strong orange or pink colour, which is enhanced with weathering, suggesting that the alteration contains an ultra-fine dusting of hematite. Potassic alteration appears to be spatially associated with certain phases (LH2) of the LHIC.

Numerous veins, vein envelopes, and fracture-filling mineral assemblages crosscut, or occur within both potassic, and to a lesser extent, albitic alteration, and are described below.

Magnetite Veins: with or without copper sulphide minerals, of variable size from fine fracture filling, to vein stockworks, to sheeted vein swarms, to 3-m to 4-m thick veins. These veins are not abundant in the Pit 3 area, but are significant in Pit 2 and comprise much of the ore within areas north of Pit 2 and east of Ingerbelle.

Pegmatite-Type Veins: coarse-grained potassium feldspar, biotite, epidote, and calcite (±albite, apatite, garnet, and quartz); these veins are distinctive and occur with or without sulphide minerals. The veins are of variable size (up to 2 m thick), variable orientation, and occur in dilatant zones throughout the camp.

Potassium Feldspar Veins: these veins range in thickness from 1 mm to 1 m and are inconsistently mineralized, filling fractures within dilatant zones across the camp.

Chlorite Veins: these veins are fine, 1 mm to 10 mm-thick, discontinuous, late, and occur throughout the camp, and are probably retrograde alteration of biotite veins.

Calcite Veins: late veins and fracture fill are ubiquitous to the mineralized area and likely reflect a collapse of the hydrothermal system.

Scapolite fracture filling is common in the Ingerbelle deposit, but is less prominent elsewhere in the Copper Mountain area. The presence of the pegmatite veins and local calc-silicate alteration assemblages can give local areas the appearance of skarn formation; however, the initial calcic minerals are themselves an alteration product, and no carbonate rocks have been recognized within the local stratigraphy.

Mining at the Copper Mountain Mine is by conventional open pit methods, using a 15-m bench height. The major components of this mining method are blasthole drilling, blasting, loading, and hauling. Pit walls are designed to geotechnical specifications and vary in slope angle depending upon lithology, alteration, and local ground conditions, with bench face angles of 70 degrees to 73 degrees, and berms of 9 m to 14 m, resulting in inter-ramp pit wall angles that range from 37 degrees to 52 degrees. Ramps are generally 33.5 m wide.

The mining schedule is based on operating 24 h/d, 365 d/a. The mine operations and mine maintenance departments’ shift schedules are planned to continue to be two 12-hr shifts per day, using four alternating crews. This schedule is quite common and acceptable in Canada. The Copper Mountain Mine provides a safe work environment, and competitive wages and benefits.

The LOM mine schedule strives to maximize the delivered mill head grade and minimize the amount of rehandle material from three pits: Copper Mountain Main pit, North Pit (Alabama), and Ingerbelle.

Mining is done on a 24 h/d, 7 d/week basis, and the mining rate varies from 150 kt/d to 200 kt/d, depending on haulage distances, ore:waste ratios, equipment availabilities, and other factors. The current long-term mine plan was generated from pit design phases based on the optimized pit shells and Mineral Reserve block models from the Copper Mountain Mine Main pit, North Pit (Alabama), and the Ingerbelle pit. The mine plan uses the designed pit shells to generate a schedule that maximizes the use of the mining fleet and provides a balance between ore and waste rock movement with a steady supply of mill feed material. The overall CMM mine plan is similar to the plan originally envisioned in the 2009 Prefeasibility Study as a series of pushbacks on the existing pits. The sequencing of the pushbacks has been modified to provide better efficiencies in mining (strip ratio) and milling (ore hardness).

The Copper Mountain Mine mill uses a simple processing flowsheet composed of primary and secondary crushing, and semi-autogenous ball mill, pebble crushing (SABC) grinding, followed by a sulphide rougher/cleaner flotation circuit.

ROM ore is fed to a gyratory 60-in by 89-in Metso primary crusher. The dump pocket is located northeast and adjacent to Pit 2. Real-time sizing cameras and belt samples support that the product produced by this unit is consistently below 127 mm. A series of six conveyor belts moves primary crusher product to the secondary crusher, or directly to the mill feed stockpile if desired.

In August 2014, a double-deck screen and a XL2000 secondary cone crusher were commissioned as part of a throughput upgrade. This crusher is fed by a 500-t surge stockpile, and can produce 24 mm mill feed.

Together, the primary and secondary crushers operate at 80% operating time, and can produce enough finely crushed material to satisfy the current milling schedule within the mine plan, plus surplus material to be used for blast-hole stemming and as a crushed road base for mining operations.

The grinding circuit is designed as a traditional (SABC) flowsheet. The semi-autogenous grinding (SAG) mill is a 34 ft by 17 ft effective grinding length (EGL) dual pinion mill with 13.56 MW of installed power. This mill operates in a closed circuit with a 12 ft by 28 ft vibrating screen, where oversized ore reports to an FLS XL900 cone crusher, with product returning to SAG feed.

The SAG is followed by two 24 ft by 40 ft ball mills operating in parallel. The ball mills are also dual pinion with identical variable frequency drive and motor installations, the same as the SAG mill (12.7 MW original to 13.5 MW upgraded). The ball mills are currently rated for a lower installed power; however, they are scheduled to be upgraded in a similar manner to the SAG in 2019.

The ball mills product is sent to the rougher flotation circuit, where it is treated by two banks of five OK 160 m3 mechanically agitated tank cells. Rougher concentrate is pumped to a 14 ft by 28.5 ft regrind mill for further liberation.

Flotation and Regrind Circuits
In August 2018, a new flash flotation circuit was installed to process a portion of regrind cyclone underflow. This circuit comprises an SK240 flash flotation cell followed by a TC5 cleaner cell. The intent of the circuit is to remove coarse liberated material to final concentrate, creating additional rougher mass pull capacity, while preventing unnecessary overgrinding, which historically resulted in gold losses.

Regrind cyclone overflow is pumped to two, 3.7 m diameter by 12 m high column cells for upgrade to final concentrate. In February 2018, these column cells were upgraded with a dynamic sparger system intended to improve fine particle and overall unit metal recovery.

In July 2019, a new second cleaner flotation circuit was installed to process flotation column concentrate. This comprises three 1.9 m direct flotation reactor (DFR) cells. This increased the final concentrate grade from 25% to 28% Cu while maintaining current levels of cleaner circuit performance.

Tailings from these columns are sent to a bank of five TK-70 m3 cleaner-scavenger tank cells. Concentrate from these cells reports back to the regrind cyclone feed pump box for further liberation. Tailings from this bank is joined by rougher tailings and reports to the TMF.

By means of smaller pump upgrades, the installation of the flash circuit, and column cell sparger upgrades, the cleaner circuit capacity has improved, allowing for higher mass pull despite the increased throughput compared to the original flowsheet design.

Gold and silver are recovered as by-products in the final copper concentrate. The historical relationships indicate that recoveries of both metals have a relationship with copper recovery, supporting an association with chalcopyrite.

Concentrate Handling
The dewatering circuit comprises a 16 m diameter, high-rate concentrate thickener, followed by a concentrate storage tank with 24 hours of capacity and a filter press containing 62 plates, each plate measuring 1.5 m by 1.5 m. Filter cake concentrate drops into a storage shed with seven days of storage capacity. Concentrate is loaded into concentrate highway trucks and trucked to the port in Vancouver to be loaded onto vessels bound for Asian smelters.

The introduction of the flash circuit has provided the indirect benefit of additional filtering capacity by means of sending coarse material directly to the dewatering circuit. This coarse concentrate filters faster, and has allowed for more capacity at the dewatering circuit.