Four (4) main styles of mineralization have been identified on the Rainy River Project:
- Moderately to strongly deformed, auriferous sulphide and quartz-sulphide stringers and veins in felsic quartz-phyric rocks (e.g., ODM/17, Beaver Pond, 433 and HS Zones);
- Deformed quartz-ankerite-pyrite shear veins in mafic volcanic rocks (e.g., CAP/South Zone);
- Deformed sulphide-bearing quartz veinlets in dacitic tuffs/breccias hosting enriched silver grades (e.g., Intrepid Zone); and
- Copper-nickel-platinum group metals mineralization hosted in a younger mafic-ultramafic intrusion (e.g., 34 Zone).

The gold mineralization is interpreted as a hybrid deposit type, consisting of an early gold-rich volcanogenic sulphide mineralization overprinted by shear-hosted mesothermal gold mineralization. Magmatic-hydrothermal copper-nickel-platinum mineralization occurs within the main auriferous zones and crosscuts the volcanogenic sulphide mineralization and the later mesothermal gold mineralization associated with the regional deformation.

Surface mining at the Rainy River Project will follow the standard practice of an open pit operation, with conventional drill and blast, load and haul cycles using a drill/truck/shovel mining fleet.

The underground mine design supports the extraction of 1,500 tpd of ore by longitudinal, longhole open stoping (“LHOS”), a mining technique suitable for the geometry and ground conditions of the Rainy River underground resources. Backfilling with cemented aggregate fill (“CAF”) is a significant aspect of the Project with respect to maximization of both resource recovery and mining productivity.

Ore occurs in sub-vertical horizons in varying widths from approximately 3 m to 20 m. Widths over 15 m are rare, and the weighted average across all zones is approximately 8 m. The ore footwall and hanging wall generally dip at 60 degrees or more, but can flatten locally to as low as 45 degrees in some areas.

Ore-grade mineralization occurs in seven independent areas of differing geometry and grade. The spatial separation defines multiple working areas that support the projected 1,500 tpd production rate, and has afforded the flexibility in the production schedule to recover higher grade material earlier in the life of mine.

The process plant facility is designed to have an availability of 92% and a capacity of 21,000 tpd (7.67 Mtpa). This includes an ultimate contribution of 1,500 tpd from the underground mine. Average head grade for the plant is 1.13 g/t Au while the design grade is 2.5 g/t Au, in order to accommodate periods of higher grade feed in the early years of the mine life. The average silver
head grade is 2.81 g/t Ag while the design grade is 6.0 g/t Ag.

Run-of-mine material will be crushed to 165 mm in a 1,372 mm x 1,905 mm gyratory crusher (596 kW) and then stockpiled. The primary crusher building houses the gyratory crusher and the tail-end of the stockpile feed conveyor.

The crushed rock will be withdrawn from beneath the stockpile, conveyed and ground to approximately 2,800 µm in an 11.0 m x 6.1 m (36' x 20'), 15,000 kW SAG mill, in closed circuit with a scalping screen and a pebble crusher. The 448 kW pebble crusher will crush the scalping screen oversize to 13 mm. The undersize from the scalping screen will be combined with the ball mill discharge and pumped to the cyclone cluster. The underflow from the cyclone cluster will feed the 7.9 m x 12.3 m (26' x 40.5') 15,000 kW ball mill. A portion of the ball mill discharge will be treated by a gravity circuit, which includes an intensive cyanidation unit and dedicated electrowinning cell. The gravity tailings will be returned to the ball mill pump box.

The cyclone overflow will be thickened in a pre-leach thickener. The pre-leach thickener underflow will be pumped to the cyanide leaching circuit with one (1) series of eight (8) 18 m diameter tanks. The leach circuit has been designed for approximately 30 hours retention time. The discharge from the leach circuit will flow by gravity to a carousel-style CIP circuit with seven (7) tanks, where the leached gold and silver will be adsorbed onto the carbon. The slurry containing the loaded carbon will be pumped from the CIP circuit and then screened, and the oversized material (loaded carbon) will be sent to the carbon stripping circuit. The pregnant solution from carbon stripping will be cooled in a heat exchanger and discharged into two (2) series of electrowinning cells. The gold and silver will be recovered as sludge in the electrowinning cells, filtered, dried and then smelted into a doré bar. The coarse spent carbon from the stripping circuit will be reactivated in a kiln, while the fine carbon will be bagged and sold for silver and gold credit.