Zancudo Gold-Silver Recovery: Gravity & Flotation Process

Source: Unnamed_Company_62 (2026)
Website: https://denariusmetals.com/project/colombia/zancudo-metals/zancudo-project-overview/

Critical Data

Overview

Denarius Metals Corp. is developing the Zancudo Gold-Silver Mineral Deposit in the Municipality of Titiribí, Department of Antioquia, Republic of Colombia. The Technical Report and Preliminary Economic Assessment (PEA), effective March 19, 2026, outlines a robust recovery method designed to process 1,000 tonnes per day (tpd) of high-grade ore. The process employs a conventional yet highly effective flowsheet comprising three-stage crushing, ball mill grinding, gravity concentration using a Knelson concentrator and shaking table, and froth flotation with rougher-scavenger and two-stage cleaning circuits. This combination targets a bulk sulfide concentrate rich in gold and silver, with overall recoveries of 85% for gold and 87% for silver. The significant head grades—6.15 g/t Au and 166.6 g/t Ag—underscore the economic viability of the Zancudo project. The process is designed to operate 24 hours per day, 365 days per year, with a process availability of 90%, ensuring consistent throughput. This integrated recovery method, detailed in the high-level process design criteria, demonstrates Denarius Metals’ commitment to leveraging industry-standard technologies to maximize precious metal extraction while maintaining operational efficiency and environmental responsibility through dry-stack tailings management.

Key Process Stages

• Stage 1: Crushing: Run-of-mine ore from the Zancudo underground mine is discharged into an ore bin and fed via a grizzly equipped chute feeder. Oversize material is processed through a primary jaw crusher (JC-01) capable of 1,000 tpd. The crushed product, combined with grizzly undersize, passes over a circular vibratory screen (VS-01) which separates the feed into coarse, medium-coarse, and fine fractions. Coarse material is further reduced by a secondary jaw crusher (JC-02), while medium-coarse reports directly to a belt conveyor. All material then passes a belt magnet (IR-01) and metal detector (MD-01) to protect the tertiary cone crusher (CC-01) operating in closed circuit. The final crushed product has a P80 of 9.60 mm, ready for grinding.
• Stage 2: Grinding and Gravity Concentration: Crushed ore (P80 9.6 mm) stored in a buffer bin is fed via belt conveyors to a primary ball mill (BM-01) operating in closed circuit with a grinding vibrating screen (VS-02). Ball mill discharge is screened; oversize returns for regrinding, while undersize reports to a pump box. Slurry is then pumped to a Knelson Concentrator (KC-01) for gravity recovery of free gold and silver. The concentrator underflow is processed on a shaking table (ST-01) to produce a high-grade precious metal concentrate (target 2% mass pull, recovering 23% Au and 10% Ag). Overflow from the Knelson and table tailings combine in a pump box before entering a hydrocyclone (HC-01) for classification. Cyclone overflow (fine material) passes through a trash screen (VS-03) and becomes flotation feed; cyclone underflow returns to the ball mill for further grinding to a target P80 of 212 microns.
• Stage 3: Rougher and Scavenger Flotation: Flotation feed enters a conditioning tank (TK-01) where reagents—collector PAX, frother MIBC, and promoter A-407—are added to render target sulfide minerals hydrophobic. The conditioned slurry then flows to a bank of five rougher flotation cells (FC-01) where air bubbles collect gold-bearing pyrite and arsenopyrite. Rougher tailings proceed to a bank of four scavenger flotation cells (FC-05) operating in series to recover remaining values. A second stage scavenger cell (FC-04) produces concentrate that reports back countercurrently to the first scavenger stage, which then returns to rougher cell number 2. The combined rougher and scavenger concentrate achieves 84.9% Au recovery and 87.4% Ag recovery at grades of 26.5 g/t Au and 640 g/t Ag.
• Stage 4: Cleaner Flotation: Rougher concentrate reports to the first cleaning stage (FC-02), where additional separation upgrades the concentrate. The first cleaner tailings return to the rougher circuit. The first cleaner concentrate then moves to a second cleaner stage (FC-03) for final polishing. The second cleaner tailings also recycle back to the rougher circuit, while the final cleaner concentrate is collected in a foam pump (PP-04) for downstream dewatering. The cleaner circuit achieves 79.4% Au and 82.7% Ag recoveries from the rougher concentrate feed, producing a final concentrate grading 31.1 g/t Au and 759.5 g/t Ag.
• Stage 5: Tailings and Concentrate Filtration: Flotation tailings from the scavenger circuit are pumped to a high-rate thickener (TH-01) with flocculant addition. The thickener underflow (high solids slurry) is transferred to a storage tank (TK-02) and then to a filter press (FP-01) for dewatering to 15% cake moisture. The filter cake is conveyed to a dry-stack stockpile for environmentally sound disposal. Clear thickener overflow is recycled back to the process. The final concentrate from the flotation circuit (0.89 dt/h) is thickened in a high-rate thickener and filtered using a filter press to 10% moisture, producing a premium bulk sulfide concentrate ready for off-take.

Additional Interesting Data and Summary

The Zancudo Project’s recovery methods are underpinned by a comprehensive High-Level Process Design Criteria (HLPDC) that defines all key variables. The grinding circuit employs a conventional ball mill with a Bond Work Index of 13.5 kWh/t, operating in closed circuit with a vibrating screen and hydrocyclone. Gravity concentration via a Knelson concentrator achieves a 2% mass pull, recovering 23% of the gold and 10% of the silver upfront, which reduces the load on flotation and improves overall recovery. The flotation circuit, using a combination of PAX collector, MIBC frother, and A-407 promoter, achieves rougher/scavenger recoveries of 84.9% Au and 87.4% Ag, with cleaner stages further upgrading the concentrate to 31.1 g/t Au and 759.5 g/t Ag. The final concentrate production rate is 0.89 dry tonnes per hour, or approximately 21.4 tpd, yielding a premium bulk sulfide product. Tailings management emphasizes environmental stewardship: flotation tailings are thickened to high density, filtered to 15% moisture, and dry-stacked, minimizing water consumption and reducing long-term liability. The thickener overflow water is recycled back to the plant, and excess water is directed to a sedimentation pond for treatment and reuse. The total make-up water requirement is only 265 m³/d, largely sourced from mine dewatering activities. Installed power across all process areas totals 3,449 HP (2,573 kW), with crushing, grinding/gravity, flotation, and tailings filtration representing the major loads. The PEA, which is preliminary in nature and includes Inferred Mineral Resources, demonstrates that this recovery flowsheet is technically feasible and economically attractive. Future optimization may include testing alternative reagent schemes or finer grind sizes to further improve recoveries. The use of dry-stack tailings aligns with modern sustainability standards, reducing the project’s environmental footprint. Denarius Metals Corp. continues to advance the Zancudo deposit through detailed engineering, with this recovery method forming the basis for subsequent feasibility studies and permitting activities in the Antioquia region of Colombia.

Key Processes: Flotation, Gravity Separation, Ball Mill, Crushing

Target Commodities: Gold, Silver