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 with its own spatial and temporal distribution.

The Copper Mountain alkalic porphyry copper-gold camp is part of a northerly-trending Mesozoic tectonostratigraphic terrane termed the Quesnel Terrane (or Quesnellia). It comprises a volcanic arc with overlying sedimentary sequences, which were built on top of a deformed, oceanic sedimentary-volcanic complex (Harper Ranch and Okanagan sub-terranes). The Quesnel Terrane was formed off-shore of the southwest of continental North America and accreted with other terranes onto North America in late Mesozoic times (Monger et al., 1992). The Nicola Group, a thick (7,000 m), Late Triassic succession of volcanic, sedimentary, and coeval intrusive rocks (Preto, 1972, 1979), underlie most of southern Quesnel Terrane.

The Eastern Belt of the Nicola Group includes the oldest rocks in the Copper Mountain camp. Within the mine area, a clear stratigraphic succession has not been defined due to extensive faulting and alteration, and probable rapid facies changes within the volcanic rocks. Dark green to black augite-porphyry flows, breccias, and possible tuffaceous material composes most of the rock types exposed in the mine area. A very fine-grained, laminated unit, referred to as a volcanic siltstone (VSLT), forms a distinct horizon (or possibly a few horizons) in the mine area. The VSLT is usually grey, but can be pale green to mauve in colour, and resembles chert. However, whole rock analyses indicated approximately 50% SiO2, and the unit is interpreted to be water lain volcanic ash and silt.

The Copper Mountain Mineral deposits are classified as alkalic porphyry copper-gold deposits. The termrecognizes the alkaline nature of the intrusive rocks associated with mineralization, where silica content is low relative to the alkali metals, sodium, and potassium. The intrusive rocks almost always have porphyritic textures, and the deposits are bulk minable. There are, however, many features of alkalic porphyry deposits that set them apart from the better known calc-alkaline porphyry copper-molybdenum deposits.

Alkalic porphyry deposits are relatively rare globally, and British Columbia contains some of the best examples within the Quesnel Terrane. Three mines (Copper Mountain, Afton-Ajax, and Mount Polley) and several other deposits and prospects form an extensive belt, stretching northwards for more than 1,000 km, with similar age and mineralization characteristics, although each deposit has its own unique features.

Alkalic porphyry deposits are markedly different from their calc-alkaline cousins, even within the samemgeological terrane, and share more similarities with iron-oxide-copper-gold (IOCG) deposits of Australiamand Chile. The distinguishing features of the British Columbia alkalic porphyry deposits include:
•Multiple deposits within a camp area
•Mineralization temporally and spatially associated with alkaline or sub-alkaline intrusions
•Early, extensive, and widespread sodic-calcic alteration
•Focused potassic alteration spatially correlated with copper and gold (±silver) mineralization
•Limited or no quartz-sericite alteration
•Structurally-controlled emplacement of mineralization as breccias, fracture fill, veins, and disseminations within both the causative intrusions and surrounding country rock
•Generally low sulphide systems, leading to presence of lower sulphur copper minerals (bornite and chalcocite), and low pyrite relative to copper sulphide and iron oxide minerals
•Abundant late carbonate alteration (calcite veining).

The low-sulphur nature of the mineralization and abundant carbonate alteration in alkalic porphyry deposits results in mines that have much lower probabilities of producing acid-generating waste rock.

Mining at the Copper Mountain Mine is by conventional open pit methods, utilizing 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 45 degrees to 52 degrees. Ramps are generally 33.5-m wide.

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 pit, Alabama pit, and the Ingerbelle pit.

The mine plan uses the optimized pit shell 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. Some capital upgrades have been installed since the initial 2011 installation to improve throughput and recovery.

In August 2018, a new flash flotation circuit was installed that treats 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 sent 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.

Tailings from these columns are sent to a bank of five, OK 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 2011 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 strong relationship with copper recovery, supporting an association with chalcopyrite.

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 48 plates, each 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 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.