The Rainy River deposit is an auriferous VMS system (Pelletier 2016) with a primary syn-volcanic source and possibly a secondary syn-tectonic mineralization event.

At Rainy River, gold and silver are the dominant metals and the base metal (Cu-Pb-Zn) sulphides, although good indicators of the presence of gold, represent less than 10%, by volume, of the host rock. This is in contrast with other VMS systems that generally contain large amounts of base metals. However, there are exceptions, i.e., gold-rich VMS deposits that often contain modest amounts of base metals relative to gold (Mercier-Langevin et al. 2015 and references therein).

The Rainy River deposit occurs within a sequence of felsic to intermediate, calc-alkaline metavolcanic rocks which is bounded to both the north and south by a lower mafic volcanic sequence. This mafic sequence is intruded by the trondhjemitic Sabaskong batholith to the north. Felsic to intermediate rocks are intruded to the east of the deposit by the Black Hawk monzonitic stock. In the deposit area all rock units strike approximately east-west and dip to the south, subparallel to the main foliation recognized in the area.

The Rainy River deposit comprises eight distinct zones of gold and silver mineralization. The bulk of the gold mineralization at Rainy River is contained in sulphide and quartz-sulphide stringers and veins hosted by felsic quartz-phyric rocks.

ODM/17 Zone
The ODM/17 Zone is a series of east-west trending, south dipping lenticular sheets hosted within calc-alkaline dacites of the intermediate fragmental volcanic succession. The zone is cut by numerous NNE trending faults. The ODM/17 Zone has presently been defined over a strike extent of 1,600 m and to depths of 975 m. The true width of the zone is approximately 200 m.

Three styles of gold mineralization are observed in the ODM/17 Zone. Low grade intervals are characterized by tightly folded pyrite stringer veins and disseminated pyrite in sericite quartzchlorite altered host rocks. Moderate-grade intervals are characterized by tightly folded and foliation parallel pyrite-sphalerite and pyrite stringer veins, commonly associated with stronger silica and weak garnet alteration.

433 Zone
The 433 Zone is located approximately 500 m north of the ODM/17 Zone and hosted within strongly sericitized calc alkaline dacite rocks and lesser tholeiitic basalts. The 433 Zone comprises a cigar-shaped lens which plunges steeply south-west. This zone has a strike length of 325 m, a vertical distance of approximately 820 m, and a true width of up to 125 m.

Gold mineralization is similar in style to the ODM/17 Zone but with a number of minor differences:
- The 433 Zone is dominated by chlorite alteration of quartz-phyric host rocks as opposed to sericite in the ODM/17 Zone.
- Chlorite-pyrite altered heterolithic conglomerates occur within the 433 Zone.
- Chalcopyrite and chlorite are associated with high-grade quartz-pyrite-gold veinlets.

Footwall Silver Zone
The Footwall Silver Zone occurs in altered dacitic tuffs and tuff breccias immediately adjacent to a high strain zone at the northern contact of the ODM/17 Zone. This zone plunges to the south west in similar orientation to the ODM/17 Zone. It is hosted by centimetre scale sulphide-bearing quartz veinlets with common millimetre scale fracture filling to dendritic native silver inclusions. Sulphides contained within these veinlets, in order of frequency, comprise pyrite, sphalerite, chalcopyrite, and galena. Localized spessartine garnets have been noted. The presence of isoclinal folding of the veinlets suggest mineralization occurred prior to or synchronous with deformation. The zone is considered to genetically related to the ODM/17 Zone. The zone is composed of numerous lenses that range from 5 to 30 m wide, have strike lengths between 5 to 50 m and plunge extents between 300 and 600 m.

HS Zones
Several subsidiary zones of gold mineralization occur between the ODM/17 Zone and 433 Zone. The HS Zones comprise a series of small, discontinuous south-west plunging, flattened shoots of mineralization. Discontinuous, irregular low-grade gold mineralization is associated with chlorite-pyrite replacement of matrix in flattened, albitized, heterolithic pebble conglomerates. The zone has a strike length of 200 m and extends to a vertical distance of approximately 700 m.

The Western Zone
The Western Zone occurs near surface approximately 500 m north-west of the western extent of the ODM/17 Zone. It is composed of stockwork of discrete centimetre scale anastomosing, folded to linear quartz and quartz-carbonate veinlets. The Western Zone is hosted predominantly within strongly deformed intermediate volcanic fragmental units (analogous to those that host the ODM/17 Zone) and mafic volcanic flows in the immediate footwall (FW) and hangingwall (HW). The Western Zone comprises a series of discontinuous 5 to 10 m wide zones of mineralization which strike approximately south-east and dip south-west at approximately 50°. Individual zones encompass a strike length of between 50 and 500 m. Collectively these zones occur over an area of approximately 500 x 1,200 m. They have been defined to down-dip depths of approximately 60 to 500 m.

The CAP Zone
The CAP Zone is located approximately 200 m to the south of the ODM/17 Zone in both tholeiitic basalts and calc-alkaline dacite of the upper diverse mafic volcanic succession. The CAP Zone has been defined over a strike length of 400 m, up to 120 m wide and with a down-dip extent of 750 m. Mineralization in the CAP Zone is open below the modelled depth. Higher-grade gold mineralization is associated with deformed quartz-ankerite-pyrite shear and extensional veins hosted by quartz-ankerite-pyrite altered mafic volcanic rocks.

Intrepid Zone
The Intrepid Zone is located approximately 800 m east of the ODM/17 Zone within dacitic\ tuffs and breccias of the intermediate fragmental volcanic succession. The Intrepid Zone has been defined over a strike length of 410 m and to 450 m down-dip. The width of the zone is variable ranging between 10 m to 60 m.

High-grade gold and silver mineralization is associated with deformed quartz-pyrite-gold, quartz-pyrite-silver, or quartz-pyrite-gold-silver veinlets that overprint other mineralization styles. The gold-silver ratio is determined by their location within the base metal zonation.

34 Zone
The 34 Zone comprises magmatic nickel copper sulphide mineralization associated with precious metals (gold, platinum group metals) within a tubular, ~100 m thick, late-stage pyroxenite gabbro intrusion which cross cuts the ODM/17 Zone and post-dates the main gold mineralization event. The host pyroxenite-gabbro intrusion is unmetamorphosed, but locally altered into serpentine and talc. Magmatic sulphides vary from massive to net-textured and disseminated. Gold and silver mineralization occur within 5 to 50 m thick dislocated (and therefor discontinuous) north-east oriented pods over a strike length of 500 m with a down-dip plunge of 100 m.

Mining at Rainy River currently uses open pit methods. It will transition into a combined open pit and underground (OP+UG) operation. Underground development commenced at Intrepid in 2021.

The open pit mine is a conventional truck and shovel mining operation, with a fleet of 220t payload haul trucks combined with diesel-powered hydraulic excavators and large front-end loaders (FELs) as primary loading units. The open pit operates at an annualized peak mining rate of 153,000 tpd of ore, and the waste has an overall strip ratio of 2.32:1 (waste:ore).

Haulage ramps were designed nominally at 33 m width and a maximum ± 10% grade, except for the bottom few benches where widths were permitted to be reduced to one-way traffic of 20 m and ± 12% grade.

The plan for the Main Zones underground operation is to access the various ore zones from two portals. The IntrepidDeposit will be accessed from one portal, with a decline started in 2021 (still under development as part of an orebody investigation project).

The underground operations will be accessed via declines and follow a mechanized longitudinal long-hole open stoping technique to mine the underground Mineral Reserves. Underground ore production rates will be variable but will reach the planned maximum of approximately 5,500 tpd in 2026.

The Rainy River mine will thus entail a continuation of the existing OP operation, plus two UG operations using mining methods optimized to the deposit’s geometry and employing long-hole (longitudinal and transverse) stoping methods. The initial main ramp will be excavated from the middle of the in-production pit to access the UG Main Zones below the pit (180 RL). Starting at the 17 East portal, the primary purpose of the ramp will be to reach the ventilation infrastructures and start pre-production in the ODM zones as soon as possible. Secondary ramps will provide access to the ODM East, Zone 433 and ODM Main Zones from the main ramp. Other secondary ramps will connect ODM Main to ODM West and ODM East to 17 East Lower. From the portal to the ODM Main ventilation raise, the total decline development length is estimated at 1,893m.

Once open pit production finishes, a second main ramp will be developed at the bottom of the pit to reach ODM Main. Both ramps will sustain material handling, personnel and equipment, but most of the production will be hauled through the ODM Main portal when available. The total projected underground development was optimized to benefit from leading-edge methods and technologies. The total project will entail around 65 km of development (horizontal and vertical) to access all six UG Main Zones: 17 East Lower, 17 East Upper, ODM East, ODM Main, ODM West and Zone 433. Zone sizes vary, but the average dips for most are between 50° and 85°.

The Intrepid Zone is the only zone with an existing portal. It is independent of the UG Main Zones. Approximately 2,644 m of total horizontal development and 168 m of Capex vertical development have already been completed at Intrepid. The portal is at 365 RL, and planned stopes are located between 300 RL and -325 RL. The zone extends approximately 300 m to 120 m horizontally and dips between 50° and 70°.

Stopes will mostly be mined using a long-hole retreat method, except where the width of the deposit is greater than 20 m and allows for a long-hole transverse method (only in the ODM Main Zone). Most stopes will be drilled as downhole unless the overcut is unnecessary or at the top of the production centres (i.e., the sill pillars). Irregularities in the lenses and geology require that waste rock gaps be used as natural pillars as much as possible.

Ore from the UG Main Zones will be mined at approximately 4,500 tpd from Q3 2026 onwards and blended with open pit stockpiles to maintain the total (UG+OP) mill feed rate at approximately 27,000 tpd until the LG stockpile is depleted. Production ramps up from Q1 2024 to Q3 2026 in the UG Main Zones to initially achieve 3,500 tpd. As soon as the second portal at the bottom of the pit is available, the production is fully ramped up to the targeted 4,500 tpd. Development production is planned with a mining contractor for the project's duration to minimize the risk of manpower shortage. Total development requirements for UG Main Zones amount to 65 km, whereas 56% is capital development.

Rockfill and CRF will also be used as backfill material in order to stabilize the excavations and maximize recovery.

Crushing
The crusher consists of a 1,400 mm x 2,100 mm, 600 kW gyratory crusher. The crusher is designed for 220 t mine haul trucks to dump directly into the crusher feed pocket. Two dump positions on opposite sides of the crusher allow for simultaneous dumping. The capacity of the dump pocket is 330 t or approximately 1.5 trucks. The crusher is equipped with a hydraulic rock breaker for reducing oversized material and a mobile crane is available for crusher maintenance.

The crusher is designed to process 1,346 tph of ore with a F100 feed size of 1,050 mm, a F80 of 550 mm and an operating availability of 65%. The crusher operates with an open side setting of 120 mm to produce a P80 product size of about 120 mm. The crusher discharge surge pocket live capacity is 418 t or approximately 1.9 trucks. Ore is removed from the discharge surge pocket by a single 2,134 mm wide apron feeder, FE01, which discharges onto the 1,372 mm wide crusher discharge conveyor, CV10. The crusher discharge conveyor then transfers ore to the 1,372 mm wide coarse ore stockpile feed conveyor, CV 11. CV11 transports the ore to the coarse ore stockpile. CV10 is equipped with a weightometer to measure the crusher production rate and total ore processed. In addition, CV10 has a metal detector that shuts down the conveyor belt automatically, permitting the operators to extract the metal detected.

The coarse ore stockpile has a total capacity of 85,700 t and a live capacity of 19,000 t. Ore is drawn from the coarse ore stockpile by three apron feeders. The apron feeders discharge onto the 1,372 mm wide SAG mill feed conveyor, which is installed in a single reclaim tunnel beneath the stockpile. The SAG mill feed conveyor has a variable frequency drive (VFD) and delivers ore to the SAG mill feed chute. The SAG mill feed conveyor is equipped with a weightometer to monitor and control the SAG mill feed rate.

Primary grinding – SAG mill
The SAG mill is an 11.0 m diameter by 6.1 m long grate discharge mill with a dual pinion drive consisting of two 7,500 kW motors with VFDs. The surveyed mill feed is a F80 of 46 mm and the discharge transfer P80 size is estimated to be 2.8 mm. The mill is currently operating at 58% of critical speed to achieve a production rate of 1,050 – 1,350 tph. The design operating power at the pinions is 12,580 kW, which is approximately 84% of the installed power. The mill currently has a grate discharge of 70 mm pebble ports.

The mill discharge is fitted with a single deck horizontal vibrating screen with 10.5 mm openings to remove oversized pebble, ball chips and tramp steel. The SAG mill currently operates with a 10% - 14% solids (v/v) ball charge made up with 130 mm balls and a total charge volume of 25% (v/v). The maximum design ball charge is 16% (v/v) with a maximum design mill fill volume of 30% (v/v).

The oversized pebble is conveyed from the SAG mill discharge screen to a Raptor L500, 3.5 m x 4.0 m x 3.6 m, pebble crusher (cone crusher), with a 447 kW drive via three conveyors, CV31, CV32, and CV33. Two belt magnets followed by a metal detector are installed on CV32. If metal is detected, a two-way gate will be opened and the metal containing ore is bypassed to a reject bin. The nominal operating rate of the crusher is 238 tph, 25% of nominal mill feed, with a design operating power draw of 235 kW. The crusher reduces the ore to an approximate P80 of 13 mm. The crushed product is conveyed to the SAG mill feed conveyor transfer tower where it is either discharged onto the SAG mill feed conveyor and recycled to the mill or fed to a bypass conveyor, which feeds a pebble stockpile adjacent to the conveyor transfer tower. The pebble crusher circuit assists in achieving the planned throughputs when the ore becomes harder. The pebble crusher circuit has been commissioned recently. The pebble crusher will not be operated unless the ore is sufficiently hard.

Secondary grinding – ball mill
The ball mill is a 7.9 m diameter by 12.3 m long overflow mill with a dual pinion drive consisting of two 7,500 kW motors with VFDs. The typical mill feed has a F80 of 2,800 µm and the resultant product size is currently a P80 range of 90 µm - 110 µm. The mill operates at 75% of critical speed to achieve a production rate of 1,050 – 1,350 tph. The design operating power at the pinions is 12,360 kW, which is approximately 82% of the installed power of 15,000 kW. The slurry discharges from the mill through a trunnion magnet for steel removal and into the cyclone feed pump box.

The ball mill is operated with a target slurry density of 72% solids (w/w) and a circulating load of 300%. The maximum circulating load is projected to be 400%. The design ball charge is 32% (v/v) with a maximum design ball charge of 36% (v/v).

The Rainy River processing plant has two main mineral processing buildings:
- Primary Crushing Building; and
- Main Process Plant.

The process flowsheet consists of the following unit processes:
• Gyratory crusher.
• Coarse ore stockpile, discharged through draw pockets by apron feeders.
• SAG mill feed conveyor.
• SAG mill.
• Pebble crusher.
• Ball mill.
• Gravity concentration of cyclone feed slurry.
• Intensive cyanide leaching of the gravity concentrate using an Acacia reactor.
• Pre-leach thickener.
• Cyanide leaching.
• CIP circuit.
• Cyanide destruction using the sulphur dioxide-air process.
• Carbon stripping using the Zadra process.
• Electrowinning of the eluent and gravity concentrate leach solution.
• Casting of gold and silver doré bars (doré) in an induction furnace.

Gravity concentration
Three ports of the cyclone feed distribution header are piped directly to ........