This report provides an update of the mineral resource estimate for the Kiena Mine Complex, incorporating historical processing data and proposed modifications for two future operational phases.
Report context
The technical report is dated January 2021 and presents an update of the mineral resource estimate for the Kiena Mine Complex, owned by Wesdome Gold Mines Ltd. The recovery methods chapter text and figures were taken directly from the 2020 Preliminary Economic Assessment (PEA) of the Kiena Mine Complex project, issued on June 17, 2020 and effective as of March 31, 2020. The 2020 MRE update does not have a negative impact on or otherwise adversely affect the mineral resource inventory that formed the basis of the 2020 PEA. The results and conclusions of the 2020 PEA are still considered current and have been carried-over for this report. Information on historical mineral processing at the Kiena mine was based on the “NI 43-101 Technical Report and Mineral Resource Estimate for the Kiena Mine Complex" in Val-d'Or, Quebec dated November 7, 2019 (Richard and Torrealba, 2019), which presented available information from Anon, 1983 and Dupont, 1996.
Processing route
The Kiena Mine processing plant became operational in September 1984. A conventional gold recovery process involving cyanidation and conventional carbon-in-pulp (CIP) was used. The principal process steps included crushing, grinding, leaching by cyanidation, gold adsorption and desorption, electrolysis, cyanide destruction, melting and casting of doré bars.
Crushing circuit
The crushing circuit starts underground with a Birdsboro Buchanan jaw-crusher, reducing the rock size to 6 inches. The former design plant throughput is 1,250 tpd, however, with the addition of a screen and cone crusher, the plant has run as high as 2,000 tpd in the past. Crushed material receiving facilities start with a 35-tonne capacity hopper equipped with a 30" x 10' vibrating feeder and a 30-inch belt conveyor, which transfers crushed material onto the existing No. 1 belt conveyor. Conveyor No. 1 transports crushed material to two coarse rock silos, each with a capacity of 600 tonnes. Material discharged from the silos is conveyed, screened and crushed to approximately 1¼" (32 mm) using a standard cone crusher (150 kW) operating in open circuit. Crushed and screened material is stored in a 1,800-tonne silo, then conveyed by vibrating feeders to the grinding circuit via a belt conveyor.
Grinding circuit
Mineralised material will be ground in a 1,000 hp semi-autogenous (SAG) mill (11'6" x 18'8") operating in open circuit, followed by a 900 hp ball mill (10'6" x 13') operating in closed circuit with two stages of cyclones for classification. If necessary, cyanide and lead nitrate can be added at the SAG mill and ball mill. The pH is controlled using quicklime in the feed to the SAG mill. Cyclone underflow is redirected to the ball mill for further grinding. Based on potential future gravity testwork, a gravity circuit (currently not shown on the process flow diagrams) may be installed and fed by a portion of the feed or cyclone underflow (to be confirmed by testwork). Cyclone overflow is pumped to a vibrating 20-mesh screen to remove trash, with screen underflow directed to a 65-ft diameter process thickener to increase pulp density.
Cyanidation
Thickener overflow is pumped to a series of three carbon column tanks where gold in solution is adsorbed by carbon. The last carbon column overflows into a carbon screen, with oversize sent to the second CIP tank and screen undersize (solution with cyanide) recycled to the grinding circuit as grinding solution. Thickener underflow is forwarded to a series of three leach tanks. Cyanide and quicklime are added to the leach feed, with lead nitrate and oxygen added to optimize gold dissolution and control pH. Retention time in the carbon columns and leach tanks is approximately 11 minutes and 36 hours respectively, based on a plant feed of 1,250 tpd.
Carbon-in-pulp process
Leach tails are pumped to the CIP circuit, composed of five CIP tanks in series. Slurry is fed at the first CIP tank. Activated carbon is fed at the last CIP tank and pumped in counter-current mode relative to the slurry. NaAu(CN)₂ molecules in solution are held by activated carbon through adsorption. Discharge from CIP tanks is pumped to a 28-mesh safety screen to recover any carbon particles. In Phase 1, slurry is sent to primary and secondary backfill cyclones, with underflow (coarse particles) sent to the backfill plant and fine particle overflow directed to the 75-ft diameter waste-thickener, from which fine slurry is sent to tailings.
Loaded carbon is pumped to the elution vessel, where gold desorption takes place using the Zadra process at 140°C and 80 psi. Pregnant solution is pumped through an electrowinning cell where gold is recovered by plating on steel wool cathodes. Cathodes are washed under pressurized water and dried sludge is melted in an induction furnace to produce doré bars.
Acid wash and carbon regeneration
Once desorption is complete, carbon is transferred to the wash vessel where it is washed with hydrochloric acid. It is then forwarded to the regeneration furnace where it is heated to 1,050°C. Finally, carbon is screened to the desired grain size for reuse.
Cyanide destruction circuit and tailings treatment
To support the planned higher tonnage in Phase 2 (year 2024 and beyond), the current process plant cyanide destruction circuit, which is not operational, will be refurbished. A filtered tailings circuit will also be added. The cyanide destruction (CND) circuit will treat thickened CIL residue slurry (tailings thickener underflow) at 60% (w/w) solids and the overflow of backfill cyclones. Addition of process water will be required to set the CND feed at 50% solids. Cyanide destruction uses the Inco SO₂/Air process.
The CND process concept considers two reaction tanks arranged in series (or parallel), providing a retention time of one hour (to be confirmed in future testwork). Liquid SO₂ is added to the tanks and process air is injected through cone spargers at the bottom of each tank to oxidize cyanide species. Copper sulphate is added to catalyze the reaction, and hydrated lime addition controls pH in each tank. An agitator in each tank ensures mixing and gas dispersion.
For the dry stack initiative, a filter plant will be installed in Phase 2. Feed to the filter plant (30 tpd capacity) at approximately 50% solids will be processed by a pre-filter thickener that increases solids to 60%. Underflow feeds a stock tank acting as buffer for the filter press circuit (two in operation, one stand-by). Dry product at 85% solids will be trucked to the tailings storage facility (TSF), and filtrate will be pumped back to the pre-filter to remove suspended solids.
Reagent systems
Reagents used in the process plant include sodium cyanide (tanker delivery, liquid, no preparation required), quicklime (truck delivery, solid, mixing tank with water addition), flocculant (bag delivery, solid, eductor and mixing tank), activated carbon (super sack delivery, solid, attrition tank mixing), anti-scalant (drum delivery, liquid, no preparation), caustic soda (tanker delivery, liquid, dilution tank), HCl (tote delivery, liquid, dilution tank), lead nitrate (super sack delivery, solid, mixing tank), liquid SO₂ (tanker delivery, liquid, pressurized system, no preparation), and copper sulphate (super sack delivery, solid, mixing tank). It is assumed that site storage capacities are sufficient for each reagent or consumable due to the lower than design throughput.
Key reported parameters
| Parameter | Unit | Original design | Phase 1 (years 2021-2023) | Phase 2 (year 2024 and beyond) | Basis |
|---|---|---|---|---|---|
| Plant yearly throughput | tpy | 400,000 | 295,010 | 310,316 | Design |
| Plant daily throughput | tpd | 1,250 | 829 | 869 | Design |
| Average Au feed grade | g/t | 7.85 | 11.7 | Design | |
| Crushing plant utilization | % | N/A | 65 | 65 | Design |
| Process plant utilization | % | 95 | 92 | 92 | Design |
| Plant hourly throughput @ % utilization | tph | 54.8 | 37.5 | 39.4 | Design |
| Gravity circuit | – | No | TBD | TBD | Proposed |
| Grind size to Leach/CIP, P80 | microns | 75 | 75 | 75 | Historical operating data |
| Leaching retention time | h | 44 | 34.1 | 32.4 | Design |
| CIP retention time | h | 4 | 6.0 | 5.7 | Design |
| Overall Au recovery | % | 96.2 | 95.7-100 | 95.7-100 | Testwork |
| Carbon stripping, regeneration capacity | t | 2 | 2 | 2 | Design |
| Residual cyanide concentration at plant discharge, (max) | – | N/A | TBC | TBC | Proposed |
| Final tailings density target | % | 32 | 53 | 85 | Design |
Project website: https://www.wesdome.com/English/operations/kiena/default.aspx
Notes: Phase 1 design values selected from highest throughput for years 2021 to 2023. Phase 2 design values selected from highest throughput for year 2024 and beyond. Grind size basis noted as based on former operation, to be confirmed in prefeasibility stage. Overall Au recovery basis noted as based on latest testwork, to be confirmed in next phase of testwork. Past throughput of up to 2,000 tpd has been processed.
Technical qualifications
The report states that due to differences in tonnage during the two operational phases, it is recommended to investigate the feasibility of using only one grinding mill (SAG or ball mill) when tonnage is less than 470 tpd, and to explore addition of variable speed drives in the mills to accommodate tonnage variations along the LOM. It is recommended to conduct an audit to validate the absence of cyanide destruction circuit during the first two years of operation. It is also recommended to investigate remaining capacity of the existing TSF to confirm need and timing for a new facility, perform a full inspection of cyanide destruction equipment available at site, and investigate location of future filter plant. More analyses and modelling are required for the new dry stack tailings management facility. A geochemical kinetic test (acid rock drainage and metal leaching) should be carried out on representative mineralized material samples from new mining zones or on representative tailings samples produced during metallurgical testing for new zones. Environmental baseline studies must be carried out early at the dry-stack location.
*Source: NI 43-101 Technical Report – Update of the Mineral Resource Estimate – Kiena Mine Complex, Wesdome Gold Mines Ltd., January 2021.*
Consolidated report summaries
The following former standalone pages about this operation were consolidated here on October 25, 2026. They are retained for source traceability; dates and figures reflect each report’s own effective date and may be superseded by the current information above.
Kiena Mine Complex Poised to Restart Processing at Reduced Throughput
Wesdome Gold Mines Ltd.’s Kiena Mine Complex in Val-d’Or, Québec, is preparing to restart its processing plant at a planned throughput of less than 1,000 tonnes per day, using the existing conventional gold recovery circuit and bypassing the secondary crusher.
The Kiena Mine processing plant, located in Val-d’Or, Québec, Canada, began operation in September 1984 and is owned by Wesdome Gold Mines Ltd. The project is a planned operation targeting gold from the Kiena Deep, Presqu’île, and Dubuisson zones. The planned operation is expected to process less than 1,000 tpd of mineralized material using the existing Kiena concentrator, with the mill performance based on a maximum of 984 tpd for the life-of-mine plan.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Plant Nominal Feed Rate (Dry) | 41.7 | tph | Design value |
| Ore Moisture | 4.0 | % w/w | Design value |
| Ore Specific Gravity | 2.80 | t/m³ | Design value |
| Average Feed Au Grade | 11.73 | g/t | Design value |
| Targeted Au Recovery – Kiena Deep | 98.5 | % | Design target |
| Targeted Au Recovery – Presqu’île | 98.5 | % | Design target |
| Targeted Au Recovery – Dubuisson | 97.0 | % | Design target |
| Ball Mill Work Index – Kiena Deep | 10.7 | kWh/t | Test result |
| Ball Mill Work Index – Presqu’île | 16.1 | kWh/t | Test result |
| A x b – Minimum – All zones | 34.0 | – | Test result |
| A x b – Maximum – All zones | 64.0 | – | Test result |
| Abrasion Index – Average – Kiena Deep | 0.196 | g | Test result |
| Specific Power – All zones | 24.7 | kWh/t | Design value |
| SAG Mill Consumed Power | 550 | kW | Design value |
| Ball Mill Consumed Power | 375 | kW | Design value |
| Recirculating Load – Nominal | 250 | % | Design value |
| Product Size (P80) – Maximum | 60 | µm | Design value |
| Leaching Circuit Retention Time | 42.8 | h | Design value |
| Carbon Concentration in CIP Tank | 20 | g/L | Design value |
| CIP Circuit Retention Time | 5.5 | h | Design value |
| Carbon Strip Vessel Capacity | 3.0 | t | Not applicable |
| Carbon Strip Vessel Bed Volume | 6.0 | m³ | Design value |
| Carbon Stripping Frequency | 0.5 | #/d | Design value |
| Carbon Stripping Solution Flowrate | 1.0 | BV/h | Design value |
| Cyanide Destruction CNWAD Target | 1 | mg/L | Design value |
| SO₂ Dosage | 8.0 | g SO₂/g CNWAD | Design value |
| Copper Sulfate Dosage | 50.0 | g Cu/t Ore | Design value |
| Cyanide Destruction Tank Retention Time | 0.86 | h | Design value |
| SAG Mill Media Consumption | 0.45 | kg/t | Estimate from historical data |
| Ball Mill Media Consumption | 0.95 | kg/t | Estimate from historical data |
| Sodium Cyanide Consumption | 0.62 | kg/t | Estimate from testwork and historical values |
| Flocculant Consumption | 0.02 | kg/t | Estimate from testwork and historical values |
| Lead Nitrate Consumption | 0.21 | kg/t | Estimate from testwork and historical values |
| Quick Lime Consumption | 1.2 | kg/t | Estimate from testwork and historical values |
| Copper Sulfate Consumption | 0.33 | kg/t | Estimate from testwork and historical values |
| Sodium Metabisulfite Consumption | 2.6 | kg/t | Estimate from testwork and historical values |
| Caustic Consumption | 0.085 | kg/t | Estimate from testwork and historical values |
| Activated Carbon Consumption | 0.08 | kg/t | Estimate from testwork and historical values |
| Fresh Water Requirement | 85 | m³/d | Design estimate |
| Total Installed Power | 3,790 | kW | Design value |
| Total Daily Power Consumption – In Operation | 53,800 | kWh/d | Design value |
| Total Daily Power Consumption – In Shutdown | 13,700 | kWh/d | Design value |
Overview
The Kiena processing plant uses a conventional gold recovery process involving cyanidation and carbon-in-pulp. The plant was originally designed for a throughput of 1,250 tpd, increasing to up to 2,000 tpd once additional crushing capacity was installed. Under the current plan, throughput will be less than 1,000 tpd. The production schedule will have a maximum of 984 tpd. The operating schedule is planned as a seven-day-per-week operation. Process tailings will be pumped to the tailings pond or sent underground as backfill.
The main process steps include grinding, cyanide leaching, gold adsorption and desorption using activated carbon, electrowinning, and cyanide destruction. The design criteria were developed based on metallurgical data from a testwork program performed on the Deep, Presqu’île, and Dubuisson zones and from bulk sample processing data. The process design criteria, along with the mass and water balance, were used to evaluate process performance.
Although grindability varies significantly between the different zones, the available power in the grinding circuit is sufficient to maintain the expected P80 of 60 µm. The mill feed will likely consist of a blend from different sources, resulting in a manageable average grindability. A complete equipment review was conducted to verify capacity and condition with respect to the expected mill throughput, reliability, operating schedule, and metallurgical performance. The review confirmed that the existing equipment is capable of meeting the throughput and performance objectives.
Key Process Stages
The crushing circuit includes a cone crusher and a screen. The objective of the crushing circuit was to increase throughput above the original nameplate capacity. As the planned throughput is below the original design capacity, crushing is not expected to be required. The operation of the existing surface crushing circuit will not be required.
The grinding circuit consists of an open-circuit SAG mill followed by a ball mill operating in closed circuit with two stages of cyclones. The main equipment includes one SAG mill 3.35 m diameter by 5.48 m long with a 1,000 hp motor, and one ball mill 3.20 m diameter by 3.66 m long with a 900 hp motor. The ground ore is thickened in a pre-leach thickener and sent to the leaching circuit.
The leaching circuit consists of three leach tanks, each 10 m diameter by 10.6 m high with 809 m³ effective volume. Cyanide, milk of lime, and lead nitrate are added to the leach feed. Air is introduced through the agitator shafts. The leach tanks operate in series. The CIP circuit consists of five CIP tanks, each 4.3 m diameter by 4.6 m high with 62.4 m³ volume. Slurry is fed to CIP tank #1, while unloaded carbon is fed to CIP tank #5.
The loaded carbon is sent to the carbon stripping circuit. Gold desorption occurs using the Zadra process in the elution vessel. The electrowinning cell is fed with pregnant solution, and gold is recovered by plating onto stainless steel wool cathodes. Gold-rich sludge is dried and mixed with flux, then sent to the gold melting furnace. The smelted product is poured into doré moulds.
CIP tails undergo cyanide destruction in one tank using SMBS, copper sulfate, and air to achieve a target of less than 1 ppm CNWAD. The tailings thickener increases pulp density before the slurry is transferred to the tailings management facility. When the paste backfill plant is operating, cyanide destruction tails are pumped to the paste backfill plant.
The water management circuit includes a fresh water tank, process water tank, mine water surface tank, and truck silo. Fresh water is supplied from De Montigny Lake. Process water will be used for most applications, supplied primarily by reclaim water from the TMF. Approximately 85 m³/d of fresh water is expected to be used in the process.
Additional Interesting Data and Summary
The process plant operating schedule will need to vary over time to operate efficiently and align with the mine production schedule. Because mine throughput will not be sufficient to maintain continuous operation at 1,000 tpd, regular process plant shutdowns will be scheduled. Critical equipment, such as the water and tailings systems, will remain in operation during these shutdowns.
The average electrical energy requirements for the process plant were determined from the equipment list and bulk sample processing data. The total installed power is 3,790 kW. Daily power consumption in operation is 53,800 kWh/d. In shutdown, daily power consumption drops to 13,700 kWh/d.
The available power in the grinding circuit exceeds the calculated requirement. Although grinding efficiency is lower than expected from testwork, the circuit can achieve the targeted size reduction. Most water requirements will be met by recycling process water.
Key Processes
- Crushing: bypassed; not required at planned throughput.
- Grinding: open-circuit SAG mill followed by closed-circuit ball mill with two stages of cyclones.
- Leaching: three leach tanks in series with cyanide, lime, and lead nitrate addition.
- Carbon-in-Pulp: five CIP tanks in series for gold adsorption onto activated carbon.
- Carbon Stripping: Zadra process for gold desorption from loaded carbon.
- Electrowinning: gold recovery onto stainless steel wool cathodes.
- Cyanide Destruction: SMBS, copper sulfate, and air in a single tank.
- Tailings Management: thickening followed by TMF or paste backfill plant.
- Water Management: reclaim water from TMF; fresh water from De Montigny Lake.
Source: NI 43-101 Technical Report and Feasibility Study for the Kiena Mine Complex, Val-d’Or, Québec, Canada, June 24, 2026. Project website: Kiena Mine Complex
