The March 2026 preliminary economic assessment for LaFleur Minerals' Swanson gold deposit describes delivering material to the Beacon Mill, a 1980s whole-material cyanidation plant under care and maintenance that needs some refurbishment.
The Beacon Gold Mill is a fully permitted whole-mineralized material cyanidation processing plant with Merrill-Crowe precipitation to recover gold, located beside a major highway and a CN rail line a short drive from Val-d'Or, Quebec. The Preliminary Economic Assessment (PEA) of Delivering Swanson Deposit Mineralized Material to the Beacon Mill, prepared by ERM for LaFleur Minerals Inc., is dated 16 March 2026. The Swanson deposit lies about 50 km from the mill by rail and highway. The Beacon mill was operated for several months in the summer of 2022, processing Beaufor mine material, and is currently under care and maintenance. Some refurbishment is required to remove bottlenecks before custom milling or before processing a planned 100,000 t bulk sample from Swanson.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Crushing plant throughput | 50 | tph | Limited by spillage and chute blockages above this rate |
| Grinding plant throughput | 35 | tph | 2022 operation |
| Tailings daily throughput | 450 to 650 | t/d | Two to four drum filters |
| Life-of-mine average grade | 1.7 | g/t Au | ERM 2025 |
| Gold extraction | 85 | % | Agnico Eagle 2009 test work |
| Crusher feed | 400 | mm F100 | 2022 operation |
| Crusher product | 9.5 | mm P100 | 3/8 inch screen |
| Grinding product | 75 | µm P80 | Agnico Eagle 2009 |
| Cyanidation leach | 32 | hours | Four agitation tanks |
| Mineralized bins | 2 | x 600 t | Final crushed material |
| Rod mill and ball mill | 8 ft x 12 ft | Not applicable | Each |
| Thickener feed | About 55 | % solids | Cyanidation thickener |
| Deoxygenation | 26 | inches of mercury | Merrill-Crowe |
| TSF permitted capacity | 1.6 | million tonnes | Cyanide tailings; 750 tpd daily permit |
| Connected power | About 2,400 | kW | 4,000 kW substation |
Overview
Dorval Mines and the Peter Ferderber Group built the Beacon mill from used and new equipment around 1985 to 1987. Monarch became the owner on 2 December 2017 when it acquired the Québec assets of Richmont Mines, then invested about $20 million refurbishing the mill in 2022, before halting operations at both the Beaufor Mine and the Beacon Mill on 27 September 2022. LaFleur acquired the Beacon Gold Mill from Monarch Mining in 2024. The process design criteria come from the existing plant, 2009 Agnico Eagle test work and information collected on the site visit.
Key Process Stages
Primary crushing
The permitted stockpile area holds about 7,000 t, including some plus 16 inch rocks that need rock breaker attention at the feed grizzly, which has a 16 inch by 14 inch opening. The jaw crusher gap is usually 3 inches, and its liners are almost new. Jaw discharge goes to a double deck screen with a one inch upper deck and a 3/8 inch (9.5 mm) lower deck. Upper deck oversize goes to a 4.5 ft standard cone crusher set at 3/4 inch closed side, and the plus 9.5 mm oversize goes to a 4.5 ft short head crusher set at 9.5 mm, or 6.4 mm if needed to reduce circulating loads. The 9.5 mm product goes to the two 600 t bins. The dust collector piping needs finishing.
Grinding
An 8 ft by 12 ft rod mill typically ran at 30 to 35 tph for Beaufor in 2022, with up to 25 m3 per hour of water, using 3 inch by 10.5 foot rods at an estimated five to eight rods a week. Dry lime and dry lead nitrate are added on the rod mill feed belt. Steel balls, under 1.5 inches, are added to an 8 ft by 12 ft ball mill, with a one-tonne bag about every two days. Two cyclones are available, fed by two 8 inch by 6 inch pumps.
Leaching
Cyanide is added at the ball mill discharge, and a small trash screen of 1 mm by 8 mm removes wood and plastic from the cyclone overflow before the cyanide thickener, at about 55% solids. Four agitation tanks with air sparging dissolve gold before four vacuum drum filters. Filtrates return to the thickener, and the cake from drum filter 4 is repulped and pumped to the tailings storage facility. A pregnant solution tank stores the dissolved gold.
Merrill-Crowe and refining
Clarified pregnant solution is deoxygenated at 26 inches of mercury, zinc dust is added to precipitate gold, and the precipitate is collected in a press. It is calcined in ovens, fluxed, melted in a graphite crucible in an electric furnace, and poured into bullion castings that are cooled, cleaned, weighed and labelled.
Tailings, reagents and water
The tailings storage facility is permitted for up to 1.6 million tonnes of cyanide tailings, with the next planned lift at dyke 3, and effluent flows from a polishing pond. A lime silo holds a full truckload, and liquid cyanide of 37% strength is stored in a 10,000 litre tank. The report cites about 95% process water recirculation, makeup from groundwater from the old mining well, and an assessed 15% to 25% water loss to evaporation and retention in the ponds. A 25 kV transformer connects the mill to Hydro-Québec.
Additional Interesting Data and Summary
The QP site visit confirmed the major equipment: instrumented PLC control, crushing plant equipment, a cyanidation circuit with a 35 t lime silo, slaking system, four agitation tanks, four drum filters, a clarifier and a Merrill-Crowe system with three presses, plus a refinery with precipitate calcination, fluxing and an electric furnace. The mill building is 27.5 m by 69 m by 15 m high.
The report also notes that the tailings pond covers 37 ha and the polishing pond 28 ha.
Key Processes
- Three-stage crushing with a double deck screen
- Rod milling and ball milling with cyclones
- Cyanide leaching in four agitated tanks
- Vacuum drum filtration of leached solids
- Merrill-Crowe zinc precipitation
- Calcining, fluxing and electric furnace refining
- Cyanide tailings storage with a polishing pond
Source: Preliminary Economic Assessment of Delivering Swanson Deposit Mineralized Material to the Beacon Mill Located in Val-d'Or, Quebec, March 16, 2026.
Project website: Beacon Gold Mill and Swanson Gold Deposit
