Significant economic Ni-Cu-PGE-Au mineralization occurs within quartz diorite offset dykes at Copper Cliff Mine offset orebodies and the Totten Mine orebodies. They can extend for many kilometres into the Sudbury Structure wall rock, and may be radial or concentric to the contact of the SIC with distinct, sharp contacts. Quartz diorite is the main component of South Range offsets, and of distal (>3 km from sic contact) portions of North Range offsets. Footwall breccia also occurs here as sheets and discontinuous lenses concentrated along the lower contact of the SIC, and as a major component of some of the offset dykes.

Mineralization consists of zones of disseminated blebby and massive Ni-Cu-PGE-Au sulphide that is spatially associated with inclusion-rich phases of quartz diorite, as well as with local structural complexities of the dykes. Ni-Cu-PGE-Au deposits have longer dip lengths then strike length and contain at least 5% sulphide. Areas between orebodies consist of barren quartz diorite or weakly mineralized inclusion-rich quartz diorite.

The Copper Cliff Mine uses Vertical Retreat Mining, Blasthole Stoping (slot-slash variation) for the bulk of the production. Sill pillars are recovered using Uppers Retreat Mining. The Copper Cliff Mine Life Of Mine Plan also makes provision for limited use of mechanized cut-and-fill mining.

Ore is transported from the Ontario Operations mines and third party ore suppliers by rail and/or truck to Clarabelle Mill where it is blended together. The ore is crushed and ground, with the majority of the pyrrhotite removed through magnetic separation and sent to a designated waste storage area in the Copper Cliff tailings impoundment area. The remaining ore undergoes selective flotation to produce a bulk nickel and copper concentrate grading 14% Ni equivalent and approximately 8.5% Cu and 11% Ni. The concentrate is dewatered, mixed with custom concentrate feed and high-grade silica flux and conveyed to the smelter. The rock tailings are used for mine backfill, building dams in the Tailings area, or disposed of in the Copper Cliff tailings impoundment area.

Concentrate produced from the flotation process is used to generate a high copper concentrate by depressing the pentlandite, thus allowing the copper to float. The concentrate is then filtered to produce a filter cake with approximate grades of 33% Cu and 0.4% Ni. This process currently generates ~500 tonnes per day of final marketable copper concentrate production and reduces the copper units sent to the smelter. This process also allows the Clarabelle Mill to accept higher copper to nickel ratio ores from the mines.

At the Copper Cliff Smelter, the nickel-copper bulk concentrate is dried and processed through two flash furnaces and five or six converters. The smelter produces a bulk matte, sulphur dioxide and slag. The sulphur dioxide from the flash furnaces is fixed in the Acid and Liquid SO2 Plants, and sold as sulphuric acid and liquid sulphur dioxide, while the lower-strength stream from the converters is vented to the stack. The slag from the furnaces is a waste product.

The converter matte is slow-cooled to produce a coarse crystal structure. It is then crushed, ground, and separated into metallics, nickel sulphides and copper sulphides by magnetic separation and flotation in the Matte Separation Plant.

All of the precious metal-bearing metallic, and some of the nickel oxide, are sent to the Copper Cliff Nickel Refinery. The remaining nickel sulphide is roasted in fluid bed roasters. The resulting nickel oxide is processed in the Copper Cliff Nickel Refinery or the Clydach Nickel Refinery, and a portion is marketed directly as nickel oxide sinter 75.

Copper sulphide from Matte Separation is treated in the MK reactor, where sulphur dioxide, as well as molten metal, is produced. The sulphur dioxide is fixed as sulphuric acid. Additional impurities are removed from the molten metal in finishing converters, producing blister copper and a nickel oxide residue. The small amount of sulphur dioxide evolved in the finishing converters is vented to the stack. The molten blister copper is transferred to anode furnaces and cast into anodes, which are then sold to or processed by others.

Nickel Refinery Process Description
The processes at Copper Cliff Nickel Refinery represents the final stage in the recovery of metallic products from mined ore before shipment to market. There are three main facilities at the Nickel Refinery – the Nickel Refinery Converter (NRC) Plant, the Inco Pressure Carbonyl (IPC) Plant and the Electrowinning Building.

At the NRC, feed input (nickel sulphide crudes, metallics, nickel oxides, precious metal baring intermediates and refinery intermediates) are charged into two Top Blown Rotary Converters (TBRCs), and melted using natural gas-oxygen lance burners. Once the temperature of the bath has reached approximately 1600ºC, petroleum coke is added to reduce the oxygen content of the bath (called reduction). High pressure oxygen is occasionally blown into the bath to desulphurize it if the sulphur content is too high. The melted product is transferred to a teeming ladle and poured through high velocity water jets (called granulation). The resultant granules are dewatered, dried in a gas-fired kiln and conveyed to the IPC.

At the IPC, the granules are batch-reacted with carbon monoxide at temperatures up to 180ºC and pressures up to 1000psi, in three 150-ton rotating reactors. Nickel and iron are extracted as carbonyl vapours, while copper, cobalt, precious metals and other impurities are retained in the residue. This residue is milled and pumped to the Electrowinning Plant. The carbonyl vapour is liquefied, purified in two parallel distillation columns and sent to decomposers. In the (eighteen) decomposers, nickel deposits from the carbonyl stream onto a stream of pre-heated nickel pellets. The remaining nickel carbonyl vapour is decomposed to produce pure nickel powder. The iron-nickel carbonyl is condensed, stored, re-vaporized and decomposed to ferronickel pellets.

At the Electrowinning Building, the IPC Residue is treated in an oxidative acid leach circuit to remove nickel, cobalt, iron, arsenic and other minor element contaminants. A second leaching circuit is used to dissolve copper, selenium and tellurium from the first leach solid residue. The slurry is filtered and the residue is sent to Port Colborne to extract the precious metals. The filtrate is pumped into tanks and an electrical current is applied through titanium cathodes and lead anodes. The copper plates onto the cathode over a two week period. The copper sheets are removed from the cathodes and sent to market. The first stage leach solution is fed to the iron/arsenic removal circuit and then through a copper clean-up circuit. The nickel and cobalt are precipitated from the solution with soda ash. The resultant carbonate stream is thickened and sent to Port Colborne.