Fenn-Gib Gold Project Recovery: Flotation & CIL Leaching

Source: Mayfair Gold Corp (2026)
Website: https://mayfairgold.ca/fenn-gib-gold-project/

Critical Data

Overview

Mayfair Gold Corp. is advancing the Fenn-Gib Gold Project in Ontario, Canada, with a comprehensive pre-feasibility study (effective December 19, 2025) that defines a robust gold recovery flowsheet. The processing plant is designed to treat 4,800 tonnes per day (1.8 Mt/a) of ore at a head grade of 1.65 g/t Au. The selected recovery methods integrate three-stage crushing, ball mill grinding with cyclone classification, followed by rougher flotation and regrind of the concentrate. A leach and carbon-in-leach (CIL) circuit then extracts gold from the reground concentrate, achieving an overall recovery of approximately 86% (based on 96% flotation recovery and 90% leach recovery). A provisional gravity circuit is included for future installation to capture coarse free gold. Cyanide destruction using the SO2/air process ensures environmental compliance. The project, located near Matheson, Ontario, is designed for a 15-year mine life with a total installed power of 15.1 MW and an estimated energy consumption of 42 kWh/t. This PFS, prepared by Ausenco Engineering Canada ULC, demonstrates a technically sound, scalable process tailored to the deposit’s metallurgical characteristics.

Key Process Stages

• Stage 1: Three-Stage Crushing — ROM ore with an F80 of 370 mm is reduced to a P80 of 12 mm using a primary jaw crusher (C150, 162 kW), secondary and tertiary cone crushers (HP350e, 286 kW each), and vibrating screens. A waste diverter allows aggregate production for on-site construction.
• Stage 2: Ball Mill Grinding & Classification — Crushed ore is fed to a 6.10 m x 8.23 m ball mill (5.5 MW) operating in closed circuit with cyclone classifiers. The target grind P80 is 106 µm. Mill discharge is diluted to 35% solids and cycloned; overflow reports to flotation while underflow returns for regrind.
• Stage 3: Rougher Flotation & Regrind — Cyclone overflow is conditioned with frother (MIBC), gold-specific collectors (AERO3501, AERO3477) and sulphide collector (PAX) before entering five conventional tank cells. Rougher flotation mass pull is 29% with a scaled-up residence time of 50 minutes. Concentrate is thickened to 50% solids and reground to a P80 of 13 µm using a 1,600 kW regrind mill. Flotation tailings are thickened to 55% solids for disposal.
• Stage 4: Leach and Carbon-in-Leach (CIL) — Reground concentrate enters a pre-aeration tank, a leach tank, and six CIL tanks (total residence time 27 hours). Sodium cyanide (0.90 kg/t) and lime (0.85 kg/t) are added. Loaded carbon advances counter-currently; gold is adsorbed onto carbon, which is acid-washed and eluted via AARL process at 120°C. Pregnant solution is electrowon and smelted into doré bars.
• Stage 5: Cyanide Detoxification & Tailings Management — CIL tailings are thickened, then subjected to SO2/air cyanide destruction in two parallel tanks (1.5 hours residence time) using SMBS, lime, and CuSO4 catalyst. Discharge target is <5 mg/L CNWAD. Detoxified tailings pass through a carbon safety screen before deposition in the TSF. Reclaim water is recovered for plant use.

Additional Interesting Data and Summary

The Fenn-Gib process plant is supported by extensive metallurgical testwork and detailed engineering. Key design parameters include a Bond ball work index of 19.0 kWh/t and a Bond rod mill work index of 21.9 kWh/t, indicating moderate hardness. The leaching circuit operates at 27 hours total residence time (pre-aeration, leach, six CIL tanks) with sodium cyanide addition of 0.90 kg/t and lime for pH control. Reagent consumption totals over 3,800 tonnes annually, including 1,633 t of hydrated lime, 1,203 t of sodium cyanide, and 606 t of sodium metabisulphite for cyanide destruction. The plant’s total installed power is 15.1 MW, distributed across crushing (1.3 MW), grinding (6.1 MW), flotation and regrind (2.5 MW), leach and adsorption (0.3 MW), desorption (0.6 MW), gold room (0.3 MW), detox and tailings (0.4 MW), reagents (0.2 MW), process services (1.7 MW), and ancillaries (1.9 MW). Water management is critical: cyanide contact water is recycled from the detox thickener overflow, while non-cyanide contact water is sourced from thickener overflows and TSF reclaim, minimizing fresh water intake. The cyanide detoxification system targets a discharge concentration of less than 5 mg/L CNWAD, ensuring environmental compliance. The TSF receives two tailings streams—flotation tailings and detoxified CIL tailings—with reclaim water returned to the plant. A gravity circuit provision (81 kW) is designed for future installation should coarse free gold be confirmed, with an intensive leach reactor (ILR) for direct electrowinning. The 15-year mine life at 4,800 t/d supports a sustainable operation, with the process plant designed for 92% grinding availability. This PFS, effective December 2025, provides a technically robust foundation for advancing the Fenn-Gib Gold Project toward construction and production.

Key Processes: Flotation, CIP/CIL, Cyanidation, Gravity Separation, Ball Mill, Crushing

Target Commodities: Gold, Copper