Rowan PEA Crushes and Samples Ore at Site, Then Toll Mills It Through an Expanded Gravity-Leach-CIP Plant in Red Lake

The 2025 preliminary economic assessment for West Red Lake Gold Mines' Rowan Project plans no mill of its own: ore is crushed and sampled at site and trucked to an existing Red Lake toll mill, which gains extra gravity, leach, CIP and detox capacity for a 97% design gold recovery.

The NI 43-101 Technical Report and Preliminary Economic Assessment for the Rowan Project, with an effective date of June 30, 2025, describes a small, high-grade underground gold mine about 16 km northwest of the town of Red Lake in northwestern Ontario, owned by West Red Lake Gold Mines Ltd. (WRLG). The 2025 study plans one year of construction, five years of operations and one year of closure. Rather than build a processing plant, the study sends Rowan ore to an existing off-site toll milling facility in the Red Lake region and proposes a set of targeted upgrades to that plant so it can handle the extra feed without losing recovery.

Critical Data

Overview

The Rowan flowsheet is split between two sites. At the mine, run-of-mine ore is stockpiled, crushed in a mobile jaw crusher and passed through a sampling tower that takes daily composite samples for assay and metallurgical accounting. The sampled ore is then stockpiled and hauled by truck to the toll mill, which operates a conventional gravity-leach-CIP flowsheet: crushing and grinding, gravity concentration, pre-leach thickening, agitated tank leaching, carbon-in-pulp adsorption, elution and electrowinning, refining to doré and cyanide destruction of the CIP tailings.

The report states that several Red Lake plants could take the ore and that one was chosen for the cost estimates because of its proximity, its infrastructure and its fit with Rowan's metallurgy. That plant could treat Rowan ore without major changes, but the report says recovery would fall short of the testwork. Testwork showed that recovery depends on strong gravity recovery and 24 to 48 hours of leach and CIP residence time, which the toll mill may not provide at a higher combined throughput. The study therefore proposes upgrades sized for the maximum 475 t/d of Rowan ore and notes that a different toll mill might need different changes of a similar size.

The metallurgy explains these choices. Extended gravity recoverable gold tests gave 93%, 95% and 76% on three master composites, with 32% to 44% of that gold in the coarse fraction. Gravity-leach tests recovered 28% to 81% of the gold by gravity alone. Sulphur dioxide and air cyanide detoxification testing showed that all four master composites could meet the target CN WAD level.

Key Process Stages

Crushing and sampling at Rowan. Run-of-mine ore feeds a mobile primary jaw crusher (a Cedarapids CRJ3042 is given as the example) that reduces it to 3 inch minus. A conveyor carries the crushed ore to an integrated crushing and sampling tower (a Westpro ST-MCP50) rated at 50 t/h. The tower has a linear cross-stream sampler, secondary jaw and tertiary roll crushing modules, a bucket elevator, a surge bin, a variable-speed belt feeder and two Vezin samplers. It produces two 25 kg composite samples a day at 3 mm minus, which go by sealed bin to an off-site laboratory. The rest of the ore goes to the sampled ore stockpile for trucking. The crusher and sampling tower run 12 hours a day, every day, on day shift only.

Secondary crushing at the toll mill. The toll mill's existing primary crusher already gives 3 inch minus feed. To hold the target grind at the higher throughput, the study adds a mobile cone screen plant as a pre-crusher (a Cedarapids CRC380XHLS is given as the example), taking the feed to 3/4 inch minus. The report says this avoids overloading the SAG and ball mills and avoids raising mill power.

Grinding. The existing SAG and ball mill circuit stays in place. With the finer feed, only minor changes are needed, such as different SAG trommel and screen apertures.

Gravity concentration. The toll mill has two Knelson XD-20 concentrators sized for its base throughput. A third XD-20, a Knelson step deck vibrating screen and a pump would be added for the Rowan feed. The report warns that without this expansion much of Rowan's gravity gold could bypass the gravity circuit and report to the leach, where it may not fully dissolve. Gravity concentrate goes to the existing CS1000 intensive leach reactor, which needs no change.

Pre-leach thickening. The existing thickener cannot handle the combined feed, so a supplementary 6 m thickener would be added to keep leach feed at 50% solids. The report found this cheaper than replacing the existing thickener with a larger one.

Pre-oxidation, leach and CIP. The current leach provides about 30 hours of residence time, which the extra feed would shorten. The study adds a 5 m by 6 m pre-oxidation tank, a 7.3 m by 8.2 m leach tank and a 3.6 m by 4.8 m CIP tank with an inter-stage screen, all agitated, and upgrades launders and piping in both circuits for the higher flow.

Carbon handling and refining. The existing acid wash, elution, electrowinning, electric kiln regeneration and induction furnace are expected to cope without changes. Loaded carbon would be pulled from the CIP circuit once a day, or twice if needed, to handle the higher gold loading. CIP and intensive leach solutions go to dedicated electrowinning cells, and the sludge is filtered, dried, fluxed and smelted to doré in a secure area.

Cyanide destruction and tailings. The toll mill's single detox tank would not give enough residence time at the higher rate, so an 8.6 m by 11.4 m tank with an agitator and pump would be added to meet the 50 mg/L CN WAD target. The toll mill's tailings facility has the space, but its next dam raise would be brought forward by about a year, and that change is in the capital estimate.

Additional Interesting Data and Summary

The study expects the toll mill's existing power supply, water supply, water treatment and reagent systems to absorb the extra load without upgrades. The added power and reagent consumption are carried in the operating cost estimate.

The report stresses that the PEA is preliminary and includes inferred resources; the 2025 resource estimate it is based on is 63% indicated and 37% inferred by tonnes. The 97% design recovery is set below the laboratory extraction of more than 99% to allow for solution losses and other inefficiencies in a commercial plant.

In summary, Rowan is a five-year, high-grade toll milling project. The only processing equipment at the mine is a crushing and sampling plant, and the design work goes into making an existing Red Lake gravity-leach-CIP mill fit the ore: more gravity capacity for its coarse free gold, a pre-crusher to protect the grind, and extra thickening, leach, CIP and detox tanks to keep residence time up.

Key Processes

• Mobile jaw crushing to 3 inch minus at the mine
• Integrated crushing and sampling tower with Vezin samplers
• Haulage to an off-site toll mill
• Cone crushing to 3/4 inch minus ahead of grinding
• SAG and ball milling
• Knelson gravity concentration with intensive leaching
• Pre-leach thickening to 50% solids
• Pre-oxidation and agitated cyanide leaching
• Carbon-in-pulp adsorption
• Acid wash, elution, electrowinning and kiln regeneration
• Induction furnace smelting to doré
• Cyanide detoxification

Source: NI 43-101 Technical Report and Preliminary Economic Assessment, Rowan Project, Ontario, Canada, 30 June 2025.

Project website: Rowan Project