Overview
Nestled in the prolific Abitibi greenstone belt of Quebec, Canada, the O’Brien Gold Project represents a significant revitalization of a historic mining district with modern mineral processing technology. Operated by Radisson Mining Resources Inc., this advanced-stage project is poised to leverage a unique toll-milling agreement with IAMGOLD Corporation to process its mineralized material at the existing Westwood complex near Rouyn-Noranda. The project centers on rejuvenating the former O’Brien Mine, which was historically Quebec’s highest-grade gold producer during its operation from 1926 to 1956. The current initiative involves processing approximately 3,000 tonnes per day of material with head grades ranging from 4.9 to 6.9 g/t Au through a sophisticated flowsheet that combines gravity separation, flotation, and carbon-in-leach technologies. This strategic approach eliminates the need for building a new greenfield processing facility, significantly reducing both capital expenditures and environmental footprint while accelerating the path to production. The project exemplifies modern mining innovation through its collaborative operational model and technically advanced recovery methods designed to achieve an impressive 87.5% life-of-mine gold recovery.
Key Process Stages
The O’Brien Gold Project employs a comprehensive mineral processing circuit that integrates both existing infrastructure at the Westwood complex with new specialized equipment. The flowsheet has been optimized through extensive metallurgical testwork to maximize gold recovery while maintaining operational efficiency and cost-effectiveness.
- Primary Crushing (Existing Equipment): Run-of-mine material from the O’Brien deposit is delivered by truck and stored on a 60,000-tonne capacity pad. A 1.07m x 1.22m jaw crusher reduces the material size before it is conveyed to milling feed bins. The crushing circuit operates at 100% availability during toll milling campaigns.
- Grinding Circuit (Existing Equipment): The comminution circuit consists of a 2,013 kW (2,700 hp) SAG mill (5.4m diameter x 6.3m EGL) in closed circuit with cyclones, followed by a 745.7 kW (1,000 hp) ball mill (3.5m diameter x 4.9m EGL). The circuit is designed to achieve a primary grind size of 75 μm (P80) at the design throughput rate of 3,000 tpd.
- Gravity Recovery Circuit (Recommissioned Equipment): The secondary cyclone underflow reports to a gravity circuit featuring a scalping screen and centrifugal Knelson concentrator operating in semi-batch mode. Gravity concentrate is further upgraded on a shaking table, with the final concentrate reporting directly to the gold room for drying and smelting. The circuit is designed to recover 42% of the gold through gravity methods.
- Flotation and Regrind Circuit (New Equipment): Secondary cyclone overflow reports to a new rougher flotation circuit consisting of four flotation cells and a conditioning tank. With a targeted mass pull of 10%, the flotation concentrate is reground to 15 μm (P80) in an IsaMill to liberate gold particles for subsequent leaching. Reagents include PAX, R208, and MIBC collectors and frothers.
- Leach and Adsorption Circuit (Existing Equipment): The reground flotation concentrate reports to primary leach tanks (10 hours residence time), while flotation tailings report to secondary leach tanks (26 hours residence time). The circuit includes three carbon-in-leach (CIL) and five carbon-in-pulp (CIP) tanks with a total adsorption residence time of 35.5 hours. Loaded carbon is advanced counter-currently for elution.
- Cyanide Destruction and Tailings Management (Existing Equipment): Tailings are treated using the SO2/air process (INCO) with a target discharge concentration of less than 1 mg/L CNWAD. Treated tailings are thickened to 53% w/w solids in a 20m diameter thickener before deposition in the existing Westwood tailings management facility.
- Electrowinning and Gold Room (Existing Equipment): Loaded carbon is eluted using a pressure Zadra system, with gold recovered from the pregnant solution via electrowinning. Gold sludge is smelted in an electric induction furnace to produce doré bars within a secure gold room facility.
Critical Data
The following table presents the key technical and operational parameters for the O’Brien Gold Project processing circuit, based on the NI 43-101 Technical Report and Preliminary Economic Assessment.
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Plant Throughput | 3,000 | tpd | Design capacity based on existing equipment |
| Mill Power (SAG) | 2,013 | kW | 5.4m diameter x 6.3m EGL mill |
| Mill Power (Ball) | 745.7 | kW | 3.5m diameter x 4.9m EGL mill |
| Target Primary Grind Size | 75 | μm (P80) | Achieved at design throughput |
| Target Regrind Size | 15 | μm (P80) | For flotation concentrate |
| Overall Gold Recovery (LOM) | 87.5 | % | Life of mine average |
| Gravity Gold Recovery | 42 | % | Design recovery to gravity circuit |
| Flotation Mass Pull | 10 | % | Target rougher concentrate |
| Primary Leach Residence Time | 10 | hours | For flotation concentrate |
| Secondary Leach Residence Time | 26 | hours | For combined material |
| Total Adsorption Residence Time | 35.5 | hours | CIL + CIP circuits combined |
| Additional Power Demand | 1.8 | MW | For new flotation and regrind circuits |
| Total Nominal Power Demand | 5.1 | MW | Complete circuit with new equipment |
| Annual Power Consumption | 43 | MWh/a | Estimated for operations |
| Sodium Cyanide Consumption | 3,023 | t/a | Estimated annual usage |
| Lime Consumption | 2,142 | t/a | Estimated annual usage |
Additional Interesting Data and Summary
The O’Brien Gold Project represents a innovative approach to modern mineral processing through its toll milling arrangement with IAMGOLD’s Westwood complex. This strategy provides significant advantages in capital cost reduction, accelerated timeline to production, and minimized environmental impact through the use of existing infrastructure. The processing circuit has been specifically designed to handle the unique characteristics of the O’Brien mineralization, which demonstrates variable competency with Bond work indices of 18.7 kWh/t (CWi), 18.2 kWh/t (RWi), and 12.8 kWh/t (BWi) at the 75th percentile.
From an environmental perspective, the project benefits from existing water management systems that source fresh water from the Bousquet River, though a comprehensive water balance was not completed for this preliminary assessment. The circuit incorporates robust cyanide destruction using the SO2/air process to meet strict environmental standards with a target discharge concentration of less than 1 mg/L CNWAD. Tailings management utilizes existing facilities at the Westwood complex, though the geochemical compatibility of O’Brien tailings with these facilities requires further investigation in subsequent project phases.
The economic assessment indicates strong viability for the project, with the combination of gravity separation, flotation, and CIL/CIP processing providing the highest net present value. The circuit design takes advantage of the coarse gold component through early gravity recovery, while the flotation circuit captures finer gold associated with sulfide minerals. The regrind of flotation concentrate to 15 μm ensures optimal liberation for maximum leach recovery.
Looking forward, the project demonstrates the growing trend of collaborative mining operations where companies leverage existing processing infrastructure to bring new deposits into production more efficiently and sustainably. This approach aligns with ESG principles by reducing the environmental footprint of mining operations and optimizing resource utilization. As the project advances to feasibility and production phases, it will contribute to Quebec’s position as a leading mining jurisdiction while providing economic benefits to the local community through employment and regional development.
Source: NI 43-101 Technical Report | Preliminary Economic | Project: Brien Gold Project | Date: June 2025
