Polymetallic Flotation at Cosalá Operations, Mexico

Source: Americas Gold and Silver Corporation (2026)
Website: https://americas-gold.com/operations/cosala-operations/

Critical Data

Overview

Americas Gold and Silver Corporation operates the Cosalá Operations in Sinaloa, Mexico, a polymetallic mining project centered on the San Rafael and EC120 ore deposits. The processing hub, the Los Braceros plant, is a conventional concentrator that has evolved from producing separate zinc and lead concentrates to currently manufacturing only copper concentrate, reflecting the shift in feedstock from San Rafael (since November 2017) to EC120 (continuous processing since August 2025). Located near the historic mining district of Cosalá, the facility achieved commercial production at San Rafael in December 2017 and overcame a prolonged illegal blockade that halted operations from January 2020 to September 2021. The significance of this plant lies in its ability to process two distinct ore types through a flexible flowsheet, achieving throughputs of 1,750 t/d for San Rafael and 1,300 t/d for EC120. The process involves three-stage crushing, primary grinding in two 600 kW ball mills, selective flotation to produce lead and zinc concentrates (historically) or copper concentrate (current), followed by thickening, filtration, and shipment. With total operating costs ranging from $15.48/t for San Rafael ore to $22.53/t for EC120 ore, the plant exemplifies cost-effective polymetallic recovery in a challenging geological and social environment.

Key Process Stages

• Stage 1: Three-Stage Crushing – Ore is fed through a 0.76 m x 1.07 m jaw crusher, followed by a 1.67 m standard cone crusher and a 1.67 m shorthead cone crusher to reduce particle size before grinding. Crushed material is stored in an 800-tonne fine ore bin.
• Stage 2: Primary Grinding – Two 3.0 m x 3.2 m ball mills, each powered by a 600 kW motor, grind the ore to the target liberation size. For EC120 ore, the circuit operates at a higher energy consumption of 34 kWh/t, reflecting the harder ore characteristics.
• Stage 3: Rougher Flotation – The ground slurry reports to Wemco 300 ft³ trough cells (lead and zinc) and 10 m³ tank cells (zinc) for initial bulk flotation. For EC120, the circuit is reconfigured to produce a single copper concentrate using a simplified reagent scheme.
• Stage 4: Cleaner Flotation – Concentrate from rougher cells is upgraded in Galigher Agitair 54C x 40 and Denver Sub-A cleaner cells to achieve final concentrate grades. A VXP500 vertical mill provides regrinding of the concentrate to liberate locked particles.
• Stage 5: Thickening and Filtration – Copper concentrate is thickened to increase percent solids, then filtered through an EIMCO rotary drum filter operating at 65% solids feed, reducing moisture to 9–10%. Filtered concentrate is weighed, stored, and loaded into trucks for transport to Impala’s warehouse in Manzanillo, Colima.

Additional Interesting Data and Summary

Beyond the core flowsheet, the Los Braceros plant incorporates a concentrate regrind circuit using a VXP500 vertical mill to enhance liberation and concentrate grade. The tailings management system is a critical component: all tailings from both San Rafael and EC120 ore are deposited in a conventional tailings storage facility (TSF) designed with east and west banks at 580 and 582 meters above sea level, respectively. By 2028, the TSF will reach its design elevation of 590 MASL, at which point additional storage capacity will be required. A filtered tailings option is under evaluation to extend the facility’s life by 6 to 7 years beyond the current life-of-mine (LOM) plan. Electrical power is drawn from the national grid, with consumption averaging 34 kWh/t processed for EC120 ore (not explicitly stated for San Rafael, though operating costs indicate $3.38/t milled for electricity). Water conservation is a key sustainability metric: between 67% and 75% of process water is recovered from tailings thickeners and recirculated from the TSF; fresh make-up water is sourced from nearby wells. Economically, the transition to EC120 processing has increased unit operating costs from $15.48/t to $22.53/t, driven by higher labour ($6.57/t), maintenance ($6.66/t), and other costs ($2.57/t), partially offset by lower reagent consumption ($1.35/t versus $3.73/t). The plant currently produces 650 dry tonnes of copper concentrate per month, shipped to Manzanillo for export. No material flowsheet changes are planned for the remaining mine life, but continuous optimization efforts target incremental improvements in throughput, recovery, and concentrate quality. The facility’s ability to process two distinct ore types—a polymetallic zinc-lead-silver ore and a copper-dominant ore—demonstrates the flexibility required to adapt to changing resource priorities and market conditions, ensuring the long-term viability of the Cosalá Operations.

Key Processes: Flotation, Crushing

Target Commodities: Gold, Silver, Copper, Zinc, Lead