Inside the Springpole Gold Project: A Deep Dive into the 30,000 tpd Flotation & Leach Processing Circuit

Overview

Nestled in the mineral-rich terrain of northwestern Ontario, Canada, the Springpole Gold Project stands as one of the country’s most significant undeveloped gold deposits. Owned and operated by First Mining Gold Corp., this ambitious project is poised to become a major contributor to Canada’s gold production landscape. The project’s location, approximately 110 kilometers east of the town of Red Lake, places it within a world-renowned mining jurisdiction with established infrastructure and a skilled workforce. The Springpole deposit is characterized by its substantial scale, hosting a large resource of gold and silver, with mineralization occurring primarily as fine-grained tellurides and within silicate minerals. This unique mineralogy presented specific metallurgical challenges that were central to the design of the processing flowsheet detailed in the December 2025 Pre-Feasibility Study (PFS). The PFS, prepared by Ausenco Engineering Canada ULC, outlines a robust and sophisticated mineral processing plant designed to handle 30,000 tonnes of ore per day (10.95 million tonnes per annum). The selection of a combined flotation and leaching circuit was driven by the need to efficiently recover gold from both telluride and silicate associations while also managing environmental obligations related to potentially acid-generating (PAG) rock. This project represents a critical step for First Mining Gold, transitioning from exploration and resource definition to detailed engineering and development, with the goal of establishing a long-life, economically viable mining operation that adheres to high standards of technical efficiency and environmental stewardship.

Key Process Stages

The Springpole processing circuit is a sophisticated integration of conventional and advanced unit operations, engineered to maximize gold and silver recovery from a variable ore body. The flowsheet is designed for high availability and incorporates specific circuits to manage different product streams for environmental compliance. The following stages outline the journey of ore from the open pit to doré bars.

• Stage 1: Primary Crushing & Stockpiling: Run-of-mine (ROM) ore is hauled from the pit and fed to a primary crusher at a rate of 1,667 tonnes per hour. The crushing circuit operates at 75% availability. Crushed ore is conveyed to a covered stockpile, providing approximately 12 hours of live storage to ensure uninterrupted feed to the grinding mill during crusher maintenance. The stockpile is equipped with apron feeders that regulate feed to the SAG mill.
• Stage 2: SAG & Ball Mill Grinding: The two-stage grinding circuit is designed to reduce ore to a target size of 150 microns (P80). It features a large, variable-speed SAG mill (10.4m x 5.2m EGL, 11.2 MW) followed by a ball mill (7.9m x 11.4m EGL, 14.2 MW) in closed circuit with a cluster of ten 750mm cyclones. The SAG mill’s variable speed drive is a key feature to accommodate the ore’s variable hardness. Ground slurry reports to rougher flotation.
• Stage 3: Rougher Flotation & Concentrate Regrind: Ground ore undergoes rougher flotation in five large 300 m³ cells. Reagents include potassium amyl xanthate (PAX) as a collector and methyl isobutyl carbinol (MIBC) as a frother. The flotation circuit produces a sulphide-rich concentrate representing 9-14% of the mass. This concentrate is then reground to an ultra-fine 17 microns (P80) using two high-intensity IsaMills (3.8 MW each) to liberate encapsulated gold and silver minerals for subsequent leaching.
• Stage 4: Parallel Leach & Adsorption Circuits: The process splits into two parallel leaching streams for environmental and metallurgical optimization. The reground flotation concentrate is thickened and leached for 12 hours in a dedicated circuit, followed by a six-thickener Counter-Current Decantation (CCD) circuit for solid-liquid separation. Simultaneously, the flotation tailings are thickened and fed to a leach and Carbon-in-Pulp (CIP) circuit with a total residence time of 16 hours, where activated carbon adsorbs dissolved gold.
• Stage 5: Cyanide Detoxification & Tailings Management: A critical environmental control step, both the concentrate CCD tails and the CIP tails undergo cyanide detoxification using the SO2/air process. This reduces Weak Acid Dissociable (WAD) cyanide to below 2.5 mg/L for safe disposal. The detoxified tailings are split; concentrate tails go to a dedicated PAG management cell, while the bulk of the flotation tails report to a co-disposal facility.
• Stage 6: Carbon Elution, Regeneration & Merrill-Crowe Recovery: Loaded carbon from the CIP circuit is acid-washed, stripped of gold using a high-temperature AARL elution process, and thermally regenerated. Gold-bearing solutions from both the concentrate CCD circuit (pregnant solution) and the elution circuit (pregnant eluate) are treated in separate Merrill-Crowe circuits. Here, gold and silver are precipitated using zinc powder, filtered, and sent to the refinery.
• Stage 7: Refining & Doré Production: The zinc precipitates are dried, smelted in an electric induction furnace with fluxes, and poured into doré bars. The refinery includes a mercury retort for safety, and the final doré bars are assayed and stored in a secure vault before being shipped to an off-site refiner.

Critical Data

The following table summarizes the key design and performance parameters for the Springpole Gold Project processing plant, as defined in the 2025 Pre-Feasibility Study.

Additional Interesting Data and Summary

Beyond the core process stages, the Springpole PFS reveals a plant designed with a strong emphasis on environmental management, reagent efficiency, and operational robustness. The decision to employ a split-tailings strategy—sending flotation concentrate tails to a dedicated PAG cell and the larger volume of flotation tails to a co-disposal facility—is a direct and proactive response to the ore’s geochemistry, ensuring long-term environmental stability. This approach is integral to the project’s social license to operate and reflects contemporary best practices in sustainable mining.

The reagent consumption data highlights the scale of operations. Key consumables include approximately 7,079 tonnes per year of sodium cyanide, 27,426 tonnes of quick lime for pH control, and 17,819 tonnes of oxygen generated by an on-site plant. The use of an IsaMill for ultra-fine regrinding, while energy-intensive (2 x 3.8 MW mills), is a technically sound choice to liberate the fine-grained and telluride-associated gold, directly targeting improved overall recovery. The plant’s design energy consumption of 29.9 kWh/tonne is a critical metric for operating costs, and the 92% availability target for the milling and leaching circuits underscores the expectation of high operational uptime.

Economically, the project’s viability hinges on the efficient execution of this complex flowsheet. The detailed handling and containment systems for all reagents, from cyanide to sulphur dioxide, demonstrate a design philosophy that prioritizes safety and environmental protection. The inclusion of a mercury retort in the gold room addresses potential minor mercury content in the ore, ensuring safe handling. Looking forward, the Springpole Gold Project, as detailed in this NI 43-101 PFS, presents a technically sound and environmentally considered blueprint for developing a major new gold mine. Its success will depend on translating this detailed design into efficient construction and operation, ultimately contributing significant gold production and economic benefits to the region of Ontario.

Source: NI 43-101 Technical Report | Pre-Feasibility | Project: Springpole Gold Project | Date: December 2025

Further Reading

• Springpole Gold Project – Canada.ca