The 2025 prefeasibility study for West Red Lake Gold Mines' Madsen Mine plans to restart the existing mill at 800 t/d, adding a semi-mobile jaw crusher and oxygen to the leach, for a life-of-mine gold recovery of 95.7%.
The NI 43-101 Technical Report and Prefeasibility Study for the Madsen Mine, with an effective date of January 7, 2025, sets out how West Red Lake Gold Mines Ltd. (WRLG) planned to restart the underground mine and mill at Madsen, about 8 km southwest of the town of Red Lake in northwest Ontario. The previous owner, Pure Gold Mining, operated the mine until it closed in October 2022, and WRLG acquired the site in 2023. The study treats Madsen as a restart rather than a new build: the grinding, leaching, carbon and refining circuits already exist, and the main process additions are a new crushing station, more oxygen in the leach and a hydraulic backfill system for tailings.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Report effective date | January 7, 2025 | Not applicable | Prefeasibility study, signed February 18, 2025 |
| Owner | West Red Lake Gold Mines Ltd. | Not applicable | Acquired the site in 2023 |
| Location | Madsen, Red Lake district, Ontario | Not applicable | About 8 km southwest of Red Lake |
| Design throughput | 800 | t/d | Steady state |
| Process plant availability | 95 | % | 35 t per operating hour |
| Crushing plant availability | 50 | % | Permitting requirement; 67 t per operating hour |
| Probable mineral reserve | 1,823 | kt | 8.16 g/t Au for 478 koz contained; effective date June 30, 2024 |
| Life-of-mine gold recovery | 95.7 | % | From plant operating data and BaseMet testwork (BL288) |
| Recovered gold, 2025 to 2032 | 457.9 | koz | Production schedule in the report |
| Grind size | 75 | µm P80 | SAG and ball mill |
| Bond ball mill work index | 9.7 to 17.1 | kWh/t | BaseMet 2018 and 2023 |
| SAG parameter Axb | 23 to 42 | Not applicable | BaseMet 2018 and 2023 |
| Bond crushing work index | 13.2 | kWh/t | BaseMet 2018 |
| Bond abrasion index | 0.24 | g | BaseMet 2018 |
| Leach retention | 24 | h | Cyanide at 150 to 170 ppm, pH 11.0 |
| CIP | 6 tanks, about 5 h | Not applicable | Carbon load 3,310 g Au/t carbon |
| Carbon stripping capacity | 1 | t/d | Can strip twice a day if needed |
| Cyanide destruction target | Below 5.0 | mg/L CN WAD | SO2/oxygen process with SMBS |
| Expected commercial production | Q1 2026 | Not applicable | As forecast in the report |
Overview
Madsen has a long processing history. The report states that the present mill was bought and relocated in the 1990s from Placer Dome's Dona Lake mine, ran at a nominal 600 t/d and used carbon-in-pulp (CIP) to recover gold. A 1998 mill report gave an average annual recovery of 90% at a head grade of 4.2 g/t. Pure Gold later brought the mine back into commercial production before the 2022 closure.
The 2025 study designs the plant for 800 t/d of ore from five lenses: Austin, South Austin, A3, McVeigh and 8 Zone. The flowsheet is primary crushing, SAG and ball milling to 80% passing 75 µm, gravity concentration inside the grinding circuit with intensive leaching of the gravity concentrate, pre-leach thickening, oxygen pre-oxidation, a 24-hour cyanide leach, CIP adsorption, acid wash, elution, electrowinning and smelting to doré on site. Tailings pass through cyanide destruction and go first to the tailings management facility (TMF). From later in Year 1, thickened tailings are to be pumped underground into open stopes as hydraulic backfill.
The mine plan covers 2025 to 2032. Head grade rises from 7.00 g/t in 2025 to 12.29 g/t in 2031, and annual recovery in the schedule ranges from 93.8% to 98.7%. The report notes that the plan uses a resource estimate dated December 31, 2021, so drilling by Pure Gold up to the closure and later work by WRLG is not included.
Key Process Stages
Crushing. Run-of-mine ore with an F100 of 500 mm will go to a new semi-mobile crushing station: a dump pocket, a vibrating grizzly feeder drawing 67 t/h, and a 112 kW jaw crusher at a 76 mm closed side setting, giving a product P80 of about 75 mm. Grizzly undersize bypasses the crusher. A stacking conveyor builds the crushed stockpile, and a loader fills trucks that haul the ore to the headframe, where it is loaded into a 600 t live-capacity bin feeding the SAG mill conveyor.
Grinding and gravity. The existing 4.9 m diameter by 1.5 m long SAG mill (560 kW) runs at 70% solids and closes with a screen. SAG discharge and ball mill discharge combine and pass over two 2 mm scalping screens. Screen undersize feeds two semi-continuous gravity concentrators, listed in the design criteria as XD20 units, which run 40 to 60 minute cycles before the concentrate is flushed to an intensive leach reactor. Gravity tailings and screen oversize go to a cluster of four 250 mm hydrocyclones (three operating, one standby) designed for a 300% circulating load. Cyclone underflow returns to the existing 2.9 m by 4.9 m overflow ball mill (560 kW). Cyclone overflow at 75 µm P80 is the leach feed.
Pre-leach thickening. After a trash screen, the slurry goes to a 10 m high-rate thickener that raises it to 50% solids with flocculant. Thickener overflow returns as grinding circuit water.
Pre-oxidation and leach. Thickener underflow is sparged with oxygen in an agitated tank to oxidize sulphide minerals before cyanide is added. The report says this reduces oxygen demand during cyanidation, cuts sodium cyanide consumption by limiting thiocyanate formation and complexing metals such as iron, and lowers reagent use in cyanide destruction. Lime dosing is being added at this stage to set pH before the leach. The leach runs for about 24 hours at 150 to 170 ppm cyanide and pH 11.0 in 7.3 m by 8.2 m agitated tanks. Oxygen was not added to the leach tanks during earlier operation. An additional oxygen generator was installed before the shutdown, and piping to bring oxygen to the leach tanks was scheduled for spring 2025.
Carbon-in-pulp. Leached slurry flows through six 3.6 m by 4.8 m CIP tanks with inter-stage screens, about 5 hours in total, with carbon moved counter-current to the slurry. The plant previously ran at about 25 g/L carbon, with 50 g/L in the first and last tanks, and the study recommends a circuit audit after restart to improve adsorption and lower the carbon concentration. A safety screen on the final tailings catches escaped carbon.
Carbon handling. One tonne of loaded carbon a day is acid washed with 3% hydrochloric acid in a fibre-reinforced plastic vessel, then stripped in a pressurized vessel with 1% sodium hydroxide and 0.1% sodium cyanide at 140°C and 450 kPa. An electric boiler supplies the heat, and a trim heat exchanger keeps the solution below 80°C before electrowinning. Immersion heaters for the barren strip tank, part of the original design but never installed, are in the expansion budget to shorten preheating. A horizontal electric kiln regenerates all of the stripped carbon.
Electrowinning and refining. Strip solution and intensive leach solution are electrowon in separate circuits. The sludge from each is filtered, dried, fluxed and smelted separately in an induction furnace to make doré, with a daily bleed of barren solution sent to the leach to control impurities.
Cyanide destruction and tailings. Two 4 m by 5 m agitated tanks, one operating and one on standby, each provide the one-hour residence time needed for the full slurry flow. The SO2/oxygen process uses sodium metabisulphite at a 5:1 SO2 to CN WAD ratio, copper sulphate at about 30 mg/L as catalyst and lime as needed to hold pH at 8.0 to 8.5, with a target below 5.0 mg/L CN WAD. Treated slurry goes to the TMF or, once the backfill system runs, underground.
Additional Interesting Data and Summary
The report lists annual reagent use at 800 t/d: 152 t of sodium cyanide, 225 t of lime, 422 t of sodium metabisulphite, 95 t of hydrochloric acid, 47 t of caustic soda, 40 t of copper sulphate, 37 t of lead nitrate, 12 t of flocculant, 9 t of antiscalant and 18 t of activated carbon. Plant water comes from the TMF, and fresh water comes from the polishing pond.
Two figures differ within Section 17 of the report. The summary and plant list give five leach tanks, while the detailed description says the slurry flows to the first of six leach tanks. The design criteria table gives one hour of pre-oxidation, while the text says about two hours of conditioning. This article uses each figure only where the report states it.
In summary, the Madsen study is a restart plan for a known CIP mill. It keeps the existing grinding, gravity, leach and carbon circuits, adds a new crusher, oxygen sparging in the leach and underground tailings disposal, and relies on plant operating data together with BaseMet testwork to support a 95.7% life-of-mine recovery at a reserve grade of 8.16 g/t.
Key Processes
- Semi-mobile jaw crushing to 75 mm P80
- SAG and ball milling to 75 µm P80
- Gravity concentration with intensive leaching of the concentrate
- High-rate pre-leach thickening to 50% solids
- Oxygen pre-oxidation ahead of cyanidation
- 24-hour cyanide leach
- Six-stage carbon-in-pulp
- Acid wash, pressure elution and kiln regeneration
- Separate electrowinning circuits and induction furnace smelting to doré
- SO2/oxygen cyanide destruction
- Tailings to the TMF and hydraulic backfill
Source: NI 43-101 Technical Report and Prefeasibility Study for the Madsen Mine, Ontario, Canada, January 07, 2025.
Project website: Madsen Mine
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.
Madsen Gold Project PEA — 2018 Technical Report
The 2018 PEA for the Madsen Gold Project outlines a conceptual process flowsheet based on an existing milling circuit previously operated at the site in the late 1990s, with design assumptions derived from historical operating data rather than new metallurgical testwork.
Report context
This technical report for the Madsen Gold Project is dated January 29, 2018, and documents a Preliminary Economic Assessment (PEA). The report describes a conceptual process for processing underground mine run (PMR) through an existing milling circuit that was originally installed at the Dona Lake Mine in late 1989 to early 1990, then moved to the Madsen site by Claude Resources and operated from 1997 through 1999. The mill has been shut down since 1999.
Processing route
Material handling and crushing
PMR would be hauled from the Madsen portal to a portable crusher unit on the mill apron. The sized material would be delivered into a 600 tonne storage bin located on the mill apron. PMR from the storage bin would be transported to the SAG mill via a SAG mill feed conveyor. The ore is discharged from the mine coarse ore bin using a coarse ore vibratory feeder. A weightometer is included on the SAG mill feed conveyor to measure the feed rate, and a magnet removes tramp steel from the mill feed.
Grinding circuit and gravity recovery
PMR, typically with a maximum size of 15 cm, would be reduced in a grinding circuit consisting of a primary SAG mill followed by a secondary ball mill. The SAG mill is 4 m diameter by 1.5 m long, equipped with a 260 kW wound rotor induction motor, and operates as a grate discharge mill with grate openings of about 1.3 cm. The SAG mill discharge is pumped across a 10 mesh sizing screen; oversize reports back to the SAG mill and undersize material reports to a pump box, then to a set of 38 cm hydrocyclones. Cyclone underflow reports to a 2.4 m diameter by 3.6 m long overflow discharge ball mill equipped with a 340 kW motor. The ball mill discharge joins with the SAG mill undersize to feed the hydrocyclone bank. PMR would be reduced from a top size of 15 cm down to 80% passing 100 microns in the grinding circuit.
A single Falcon concentrator is included in the underflow stream of one of the hydrocyclones in the grinding circuit to recover any coarse free gold from the mill feed. The Falcon concentrate reports to a concentrate surge tank and is then transported via pump to the refinery area. A gravity concentration table further upgrades the Falcon concentrate prior to processing in the induction furnace to produce bullion bars. Gravity concentrator tailing is returned to the cyclone feed pump box.
Pre-leach thickening
The cyclone overflow (ground feed) passes over a screen for wood and trash removal ahead of the gold recovery circuits. Slurry is thickened to about 50 percent solids in a 15 m diameter pre-leach thickener. Water removed is recycled back into the grinding process. Thickened slurry is pumped to the first tank in the cyanidation circuit at approximately 55 percent solids.
Cyanidation circuit
The cyanidation circuit consists of a series of five agitated leach tanks. The first tank is a pre-aeration tank where air is injected to pacify cyanide-consuming species in the feed. At a processing rate of 600 tonnes per day, the residence time in each of the five cyanidation tanks is about 10 hours per tank. Starting at the number 2 leach tank, sodium cyanide is stage added to facilitate the dissolution of gold. Lime is used to maintain alkalinity at about pH 11, and lead nitrate is also stage added.
Carbon-in-pulp (CIP) circuit
Slurry from the cyanidation tanks passes across a trash screen prior to being pumped to the CIP tanks. The CIP circuit consists of six agitated tanks with a residence time of about one hour for each tank at the anticipated mill feed rate. Gold is transported from the solution phase of the slurry onto the surface of activated carbon contained in each CIP tank. Carbon movement in the CIP circuit is counter flow to the slurry: carbon is advanced from tank 6 to tank 1, while slurry moves from tank 1 to tank 6. Interstage screens in each CIP tank allow carbon to remain captive while slurry flows through by gravity. Loaded carbon is removed from tank 1 and advanced to the strip circuit. Slurry depleted of gold content discharges from the last CIP tank (tank 6) and passes over a safety screen to capture any escaping carbon, then is pumped to the tailing storage area.
Elution and carbon regeneration
Loaded carbon is advanced from the number 1 CIP tank to a one tonne carbon strip vessel. Stripping is carried out under elevated temperature and pressure on a batch basis, with one tonne batches processed every 24 hours. Loaded solution from the strip circuit is advanced to the electrowinning circuit. Stripped or barren carbon is discharged and fed to a carbon re-activation kiln to burn off impurities and restore carbon activity before it is re-circulated back into the number 6 CIP tank.
Electrowinning and refining
Gold is recovered from loaded strip solution in an electrowinning cell equipped with stainless steel wool cathodes. Gold is deposited on the surface of the steel wool using electrochemical principles. The gold is washed off the steel wool and then dried. Both the dried sludge from the electrowinning process and the gravity product are melted at high temperature in an induction furnace to produce high grade doré bars containing gold with silver and other minor impurities. Bullion bars are sent to an external refiner for further upgrading.
Cyanide destruction
The report states that it has not been confirmed if cyanide destruction will be required. The assumption for this PEA is that tailings will be pumped to the existing tailing storage, where residual cyanide and metals will dissipate by natural degradation. This item is noted as requiring further modelling or testing in the next phase of work.
Tailing management
The tailings management facility at the Madsen Gold Property has been in operation since the late 1930s and has undergone several modifications. In the 1950s, containment structures were constructed using tailings. In 1997, two rock fill tailings dams were constructed to create a distinct tailings pond and a polishing pond. Subsequent modifications have been made to address stability and flood routing issues. The existing TMF was designed to withstand a 100-year rain or snow event. It is anticipated that the current available capacity in the tailings pond will need to be extended for the envisioned project.
Key reported parameters
| Parameter | Value | Units | Basis |
|---|---|---|---|
| Mill feed rate (design) | 600 | tonnes per day | Historical operating data |
| Mill feed rate (design) | 23 | tonnes per hour | Historical operating data |
| PMR top size to grinding | 15 | cm | Design assumption |
| Grinding product size | 80% passing 100 | microns | Design target |
| SAG mill dimensions | 4 m diameter x 1.5 m long | Existing equipment | |
| SAG mill motor | 260 | kW | Existing equipment |
| Ball mill dimensions | 2.4 m diameter x 3.6 m long | Existing equipment | |
| Ball mill motor | 340 | kW | Existing equipment |
| Pre-leach thickener diameter | 15 | m | Existing equipment |
| Pre-leach thickener underflow solids | 50 | % | Design target |
| Number of cyanidation leach tanks | 5 | Existing circuit | |
| Leach tank residence time per tank | 10 | hours | At 600 tpd design rate |
| Number of CIP tanks | 6 | Existing circuit | |
| CIP tank residence time per tank | 1 | hour | At 600 tpd design rate |
| Strip vessel capacity | 1 | tonne | Batch basis, every 24 hours |
| Historical gold recovery range | 90 – 94 | % | Actual operating data |
| Assumed gold recovery in PEA | 92 | % | Routinely achieved during operation |
| Mill operating cost (with contingency) | 28.27 | $/tonne milled | Estimated |
| Mill capital cost (with contingency) | 11,019,000 | $ | Estimated refurbishment |
| Power consumption | 30.0 | kWhr/tonne | Assumed |
| Power cost | 0.10 | $/kWhr | Assumed |
Project website: https://westredlakegold.com/madsen-mine/
Technical qualifications
The report states that metallurgical testing has not been completed to establish the design criteria for this PEA study. All assumptions regarding reagent consumption and mill recovery have been derived from actual operating data from the plant when it operated at the Madsen Mine from 1997 through 1999. The report notes that during the operating period, ore from the McVeigh deposit made up a portion of the mill feed and that when consistent feed came from the McVeigh deposit, historical data showed recoveries higher than 92%. The report also notes that relatively low recoveries achieved during the 1990s are attributable to fluctuations in tonnage of daily feed available and that feed came from multiple deposits including the number 1 Shaft area and the Buffalo deposit, which accounted for feed grades consistently lower than planned.
The report also states that it has not been confirmed if cyanide destruction will be required, noting that further modelling or testing is needed in the next phase of work. The existing mill has been shut down since 1999, and all electrical equipment will require testing for serviceability as a next step. The capital estimate includes an allowance for replacement and repair of electrical gear as required.
*Source: Madsen Gold Project PEA, January 29, 2018, Section 17 – Recovery Methods*
Madsen Mine: High-Efficiency Gold Processing Circuit
Overview
The Madsen Mine in Ontario, Canada, operates a sophisticated gold processing plant capable of achieving 95.7% gold recovery through a combination of gravity concentration, cyanide leaching, and carbon adsorption. The facility processes 800 tonnes per day (tpd) of ore from five distinct lenses, delivering gold doré bars on-site.
Key Process Stages
- Primary Crushing: Semi-mobile jaw crusher reduces ROM feed (F100: 500 mm) to P80 of 75 mm
- Grinding: SAG mill (4.9m x 1.5m, 560 kW) and ball mill (2.9m x 4.9m, 560 kW) achieve final P80 of 75 µm
- Gravity Concentration: Two semi-continuous concentrators recover free gold from SAG/ball mill discharge
- Pre-Oxidation: Oxygen-sparged agitation tank (2-hour retention) optimizes leaching conditions
- Cyanide Leaching: Five tanks (24-hour retention) operate at 150-170 ppm NaCN and pH 11.0
- CIP Adsorption: Six-tank circuit (5-hour retention) with carbon concentration of 25-50 g/L
- Carbon Processing: Acid wash (3% HCl), pressurized elution (140°C, 450 kPa), and thermal regeneration
- Electrowinning: Dual-circuit system processes strip solution and intensive leach concentrate
- Cyanide Destruction: SO2/oxygen process reduces CNWAD to <5 mg/L in agitated tanks
Critical Data
| Parameter | Value | Source |
|---|---|---|
| Throughput | 800 tpd | SRK Mine Plan |
| Gold Recovery | 95.7% | BaseMet Testwork (BL288) |
| Bond Ball Mill Work Index | 9.7-17.1 kWh/t | BaseMet (2018, 2023) |
| Leach Retention Time | 24 hours | Operational Data |
| CIP Carbon Load | 3,310 g Au/t | Vendor Model |
| NaCN Consumption | 152 t/yr | BaseMet (2018) |
Innovations
The plant features oxygen injection in pre-oxidation and leach circuits to enhance metallurgical performance, along with a hydraulic backfill system for tailings management starting in Year 1. The carbon regeneration kiln processes 1 tpd of activated carbon with integrated heat recovery.
Based on filing data from 2024-2025.
