Eagle’s Nest is a sub-vertically dipping body of massive magmatic sulphides (MMS) in the form of a flattened pipe approximately 200 m long and 60 m thick, and currently defined vertically to 1,650 m. The deposit remains open along strike and occupies the northwestern margin of a vertically-inclined serpentinized peridotite dyke that is present in subcrop over a north-south strike length of about 500 m with a maximum width of about 75 m. The massive sulphides within the top 250 m are confined to a volume occupying the northwestern tip of this body, and are bordered to the southeast by a thicker zone of net-textured sulphide hosted by serpentinized peridotitic cumulates. Below 250 m, the massive sulphides can be found throughout the mineralization and, in some cases, into the surrounding granodiorite. The dyke is open at the north and south ends, and plunges very steeply to the south or vertically. The exact attitude of the sulphide-filled keel at the northern tip of the dyke is impossible to state because of the irregularity of the contact. Although a considerable amount of local deformation is evident around the contacts, particularly where they are occupied by massive sulphide, the body appears to be essentially still in place and not significantly deformed.

The Eagle’s Nest deposit mineralization is confined within a single ultramafic unit and, therefore, no geological domains are applicable to the resource estimation process. The deposit comprises two segments – the Main Zone and the East Zone. The Main Zone is a pipe-like body that dips sub-vertically with the longer axis in the dip direction. It is approximately 200 m along strike in a north-south direction, 40 to 60 m wide and is open at depth beyond 1,500 m below surface. The East Zone is a north-south striking tabular body, about 200 m east of the Main Zone. Its dimensions have not been fully established as it is open-ended along both strike directions and at depth.

The Ni-Cu-PGE mineralization is associated with massive/semi-massive, net-textured and disseminated sulphides. The major sulphide minerals identifiable with a hand lens are pyrrhotite, pentlandite and chalcopyrite with accessory magnetite. The pattern of distribution of the sulphides is not discernible due to one or a combination of the following factors: (a) the drill holes intersecting the deposit are at highly variable angles, (b) extreme physical deformation, as evidenced by the narrowing and twisting of the Main Zone 100 m below surface coupled with metamorphism, have obliterated the original fabric of the minerals and the overall geometry of the bodies. Thus, wire-framing to differentiate the three sulphide mineralization patterns is not possible or practical. Despite the obliteration, drill hole intercepts show that Ni-Cu-PGE are concentrated in the same broad zone. There is no geological reason to believe that massive sulphides would be restricted to the upper, middle or lower zones of the deposit.

Due to its geometry, moderate grade and strong host rock, the deposit is ideally suited for vertical bulk mining using blast hole stoping techniques. The Feasibility Study is based on blast hole stopes 20 m wide and 50 m high across the width of the orebody. Below 225 m L, 100-m stope heights are being considered as a cost improvement measure. The stope height is based on the current accuracy and capacity of longhole drill technology and a marginally high powder factor will be used to maximize blast fragmentation. The longer, 100-m holes would not be drilled until the fifth year of production, by which time significant experience will have been gained drilling 50-m holes and improvements in drill technology are also likely. The compactness of the Eagle’s Nest deposit allows short underground travel distances and it is expected that, with good fragmentation, rock handling through main passes to feed the main crushing station will be extremely efficient.

The mining method will use the most advanced proven technology available. The main telecommunication/computer networking system will originate from the underground operations centre. This system will connect to field mining equipment used in delineation drilling, development, production, backfilling and infrastructure support systems, such as ventilation, dewatering, electrical and micro-seismic monitoring.

Paste backfill will be used in the Eagle’s Nest mine. The backfill plant will be installed at the processing plant level of the mine. This system will provide a cemented paste backfill to fill the stopes in the mine replacing the 3,000 t/d of ore mined.

The development equipment fleet will consist of jumbo drills, machines for loading of emulsion explosives, manual connection of computer-based detonators and primers, load-haul-dump (LHD) machines, ground support equipment and trucks.

Production mining equipment will consist of a fleet of longhole production drills, emulsion explosives loaders with manual charging of the loaded holes, LHD machines and haulage trucks. Two fleets of equipment, with computerized systems installed, will be needed to support the production goals.

The Eagle’s Nest project is envisaged to be a 3,000 t/d (1,095,000 t/y) nickel-copper ore processing facility. The process comprises conventional crushing, grinding, flotation and concentrate dewatering to produce a single concentrate containing typically 10.2% Ni, 5.7 % Cu, 19 g/t Pd, 5 g/t Pt, 1 g/t Au and 13 g/t Ag.

The life-of-mine average metallurgical recoveries are estimated to be 83.1% for Ni, 89.7% for Cu, 82.3% for Pd, 74.0% for Pt and 76.7% for Au.

The run-of-mine ore (ROM) will be delivered to a 600 mm by 600 mm grizzley and crushed using a primary jaw crusher. Oversize will be broken using a hydraulic boom breaker. The crushed product will be conveyed to either the 3,000-t capacity net-textured crushed storage bin or the 3,000-t capacity massive ore storage bin. Net-textured and massive mineralization will be campaigned separately through the crushing facility.

Feeders below the net-textured and massive crushed ore bins will feed onto their respective net-textured and massive SAG mill feed belt conveyors, both equipped with a belt scale. The products from the net-textured SAG mill (5.0 m by 5.0 m EGL, with 1,600-kW motor) and the massive ore SAG mill (3.5 m by 3.5 m EGL, with 500-kW motor) the will be screened, and oversize material (pebbles) will be conveyed to a pebble crusher. The cone crusher will process pebbles from both the massive and net-textured grinding circuits and the product will discharge onto the net-textured SAG mill feed conveyor.

The fine discharge from the massive SAG mill will be pumped to a cyclone cluster, the cyclone overflow product, with a target particle size of P80 100 µm, will be forwarded directly to the primary flotation cleaning circuit. Underflow will go to a ball mill for further grinding.

The fine product from the net-textured SAG mill will be combined with the secondary ball mill discharge and pumped to a nest of cyclones. The cyclone overflow with a target particle size of P80 55 µm will feed the rougher flotation circuit and the underflow will feed the ball mill (5.0 m diameter by 8.2 m EGL with 3,550-kW motor).

The Feasibility Study assumes that a single bulk copper-nickel-PGM concentrate product will be produced.

The net-textured flotation circuit comprises aeration rougher flotation, rougher cleaner flotation to reject pyrrhotite and non-sulphide gangue, scavenger flotation, re-grinding of scavenger concentrate, scavenger cleaning and scavenger cleaner scavenging flotation. The flotation cells selected by Outotec were based on kinetic studies.

The rougher concentrate will be directed to the first cleaning circuit, where it joins the aerated massive ore cyclone overflow stream. The scavenger concentrate will feed the regrind circuit and the scavenger tailings will be pumped to the tailings thickener.

Prior to the cleaning stage the massive ore cyclone overflow product will be aerated by two aeration tanks. The concentrate from the cleaner cells will be pumped to the concentrate thickener and the cleaner tailing will feed the regrind circuit.

The feed of the regrinding circuit comprises the scavenger concentrate, first cleaner tail, scavenger cleaner scavenger concentrate and scavenger re-cleaner tailings. The purpose of the regrind mill circuit is to produce a product with a target P80 of 35 µm.

The overflow of the regrind circuit cyclones will feed the scavenger cleaner circuit, which comprises six (scavenger cleaner) and two (scavenger cleaner scavenger) flotation tank cells. The concentrate from these scavenger cleaner cells will feed a scavenger re-cleaner circuit containing three flotation tank cells. The concentrate from the scavenger re-cleaners will join the cleaner concentrate and be pumped to the concentrate thickener.

The cleaner concentrate and scavenger re-cleaner concentrate will be combined into a single product and partially dewatered underground using a 14-m diameter high rate thickener. The thickener underflow will be stored in two 600-m3 agitated holding tanks which will ensure that there will be enough underground storage capacity prior to pumping thickened concentrate to the surface for filtering. Pumping to surface will be undertaken using positive displacement pumps.