This report summarizes the processing methods and design criteria for the Spanish Mountain Gold Project, based on a Preliminary Economic Assessment (PEA) technical report dated 2025.
Report context
The Spanish Mountain Gold Project technical report, dated 2025, presents the results of a Preliminary Economic Assessment (PEA) for the Spanish Mountain Gold deposit. This article focuses specifically on Section 17 (Recovery Methods) of that report, which describes the proposed process plant design, metallurgical test work outcomes, and associated infrastructure for a 10,000 tonnes per day (t/d) concentrator. All processing information is derived from the PEA-level design and metallurgical testing described in the source report.
Processing route
Process flowsheet overview
Metallurgical test work results confirm that run-of-mine (ROM) ore from the Spanish Mountain Gold deposit can be processed using a conventional flowsheet consisting of:
- Crushing
- Grinding
- Flotation
- Gravity concentration of cleaner and re-cleaner flotation tails
- Carbon-in-Leach (CIL) of combined flotation and gravity concentrates
- Carbon elution and electrowinning
- Cyanide destruction of CIL residues with the SO₂/Air process
Unit processes selected for the plant design are based on the results of metallurgical testing. The PEA process produces gold-silver doré as a final product.
Crushing
Crushing will be carried out using a three-stage crushing circuit with a capacity of 595 tph and 73% availability. The circuit includes:
- Primary jaw crusher operating in open circuit with a closed size setting (CSS) of 175 mm
- Secondary cone crusher with single deck screen, operating in open circuit with a CSS of 55 mm
- Tertiary cone crusher with single deck screen, operating in closed circuit using two short head cone crusher stations with pre-classification vibrating screens
ROM ore is hauled to the primary crusher using 90-tonne payload haul trucks, which dump onto a static grizzly. A tramp magnet removes steel from the primary crushed ore conveyor before the secondary crushing stage. Final crushed product with P₈₀ of 12 mm is conveyed to a 20,000-tonne fine ore bin.
Grinding
Grinding from P₈₀ 12 mm to P₈₀ 180–184 μm is carried out by a ball mill in closed circuit with a cyclone. The grinding circuit processes a nominal 10,000 tpd at 453 tph with 92% availability and 250% recirculating load. The ball mill measures 16.5 feet diameter by 30 feet length with a 3,700 kW motor. The mill feed particle size F₈₀ is 12.0 mm, with mill product P₈₀ at 184 μm.
Flotation
Cyclone overflow from the grinding circuit is pumped to a flotation conditioning tank. Potassium amyl xanthate (PAX) is used as a general-purpose flotation collector, and methyl isobutyl carbinol (MIBC) is used as a frother.
Rougher flotation is carried out in nine conventional 40 m³ mechanical cells, each using forced air, providing 18 minutes residence time. Rougher flotation tails are pumped to the tailings thickener.
Rougher concentrate gravity flows to cleaner and recleaner flotation where carboxymethylcellulose (CMC) is used to depress organic carbon. Cleaner flotation uses three 18 m³ cells with 13 minutes residence time. Recleaner flotation also uses three 18 m³ cells with 13 minutes residence time. Recleaner concentrate is pumped to a concentrate thickener.
Cleaner and recleaner tails gravity flow to a semi-batch gravity centrifugal concentrator (Sepro SB5200). Gravity tails are pumped to the tailings thickener. Gravity concentrate is transported to the concentrate thickener.
Regrind
Concentrate production is estimated at 3.4% of mill feed. Thickener overflow from the concentrate thickener gravity flows to a tank where it is recycled for plant use. Thickener underflow is pumped at 40% solids to a 200 kW vertical regrind mill. Regrind product at approximately P₈₀ 35 μm is pumped to CIL for leaching.
Carbon-in-Leach (CIL)
Leach feed from the regrind mill is pumped to a CIL feed sampler, then contacted with carbon using six CIL tanks operating in series, providing 48 hours total residence time. Each tank is 6.2 m diameter by 7.8 m height. Sodium cyanide and lime slurry are added to CIL Tanks 1 and 3.
Carbon concentrations of 15–20 g/L are required in all tanks. Barren carbon enters the adsorption circuit at CIL Tank 6 and moves countercurrent to slurry flow using interstage screens and pumps from downstream to upstream tanks. The countercurrent process is repeated until carbon becomes loaded and reaches CIL Tank 1. Carbon is then moved to a loaded carbon recovery screen, washed with water, and pumped to the desorption area. Underflow from the loaded carbon recovery screen is returned to CIL Tank 1.
Slurry from CIL Tank 6 flows by gravity to a carbon safety screen to recover any carbon in the event of damage to the CIL Tank 6 interstage screen. Recovered carbon is collected in a bin for manual transfer. Underflow from the carbon safety screen gravitates to a cyanide destruction tank.
Carbon desorption and regeneration
Carbon desorption and regeneration is carried out by acid washing of carbon, stripping of gold from loaded carbon (elution), and carbon regeneration.
Carbon from the loaded carbon screen is pumped to an acid wash with dilute hydrochloric acid, using an acid wash column inside an acid-proofed concrete bund to contain spillage.
After acid wash, carbon is pumped to an elution circuit with elution columns, a strip solution tank, a strip solution pump, and a strip solution heat exchanger. The elution circuit operates in closed circuit with electrowinning cells. Strip solution heat exchangers maintain the strip solution at 145 °C during the stripping cycle and ensure the temperature of solution entering the electrowinning cells is below 100 °C.
Eluate flows from the top of the elution column to a loaded solution tank after cooling through heat exchangers. Eluate is pumped to electrowinning cells to recover gold and silver as sludge. Barren solution from electrowinning gravitates back to the strip solution tank. The sludge is drained from the electrowinning cells and vacuum filtered before refining.
Refining
Filtered cake from electrowinning is dried in two drying ovens and directly smelted with fluxes in two induction furnaces. Gold-silver doré is poured into moulds, weighed, stamped, sampled, and stored in a safe ready for dispatch. Furnace exhaust is passed through a wet scrubber to remove entrained particles and vented through a stack.
Detoxification
Tails from CIL are thickened and fed to a detox reactor at 45% solids w/w. Cyanide destruction uses the SO₂/Air process with sodium metabisulphite. Slurry from the detoxification stage is pumped to the final tailings thickener. An HCN detector monitors airborne gas, and a cyanide analyzer monitors cyanide levels to ensure target levels are achieved.
Tailings thickener
The final tailings thickener combines tailings streams from flotation and detoxification. Thickener overflow is recirculated to the process water system. Thickener underflow is pumped to the tailings storage facility at 50% solids. The thickener is 30 m in diameter with underflow density of 65% solids.
Process water and power
Raw water is pumped to a fresh water storage tank (14 m diameter, 18 m height). Make-up water and fire water for the plant are drawn from the fresh water tank. Recycled plant water is pumped to a process water tank (18 m diameter, 18 m height). A detailed plant water balance has not yet been completed.
Site power is estimated at 10.5 MW, with process facilities estimated to use up to 9 MW for operations.
Assay and metallurgical laboratory
The assay laboratory will be equipped with sample preparation equipment, fire assay equipment, atomic absorption spectrophotometer (AAS), and Leco furnace. The metallurgical laboratory will undertake test work to monitor metallurgical performance and improve process flowsheet operations, equipped with laboratory crushers, ball and stirred mills, particle size analysis sieves, flotation cells, filtering devices, balances, and pH meters.
Key reported parameters
| Parameter | Unit | Value |
|---|---|---|
| Mill Feed Throughput | tpa | 3,650,000 |
| Plant Availability | % | 92 |
| Plant Daily Throughput | tpd | 10,000 |
| Plant Hourly Capacity | tph | 453 |
| Average ROM Feed Au Grade | g/t | 1.00 |
| Max ROM Feed Au Grade | g/t | 1.50 |
| Crushing | ||
| Crusher Work Index | kWh/t | 9.5 |
| Primary Crusher Type | , | Jaw |
| Secondary Crusher Type | , | Cone |
| Tertiary Crusher Type | , | Cone |
| Fine Ore Bin Capacity | tonnes | 10,000 (Section 17.2) / 20,000 (Section 17.3.1) |
| Grinding | ||
| Bond Work Index | kWh/t | 12.2 |
| Ball Mill Dimensions | Dia ft x EGL ft | 16.5 x 30 |
| Ball Mill Power | kW | 3,700 |
| Mill Feed F₈₀ | mm | 12.0 |
| Mill Product P₈₀ | μm | 184 |
| Rougher Flotation | ||
| Residence Time | min | 18 |
| Number of Cells | number | 9 |
| Cell Volume | m³ | 40 |
| Cleaner Flotation | ||
| Residence Time | min | 13 |
| Number of Cells | number | 3 |
| Cell Volume | m³ | 18 |
| Re-Cleaner Flotation | ||
| Residence Time | min | 13 |
| Number of Cells | number | 3 |
| Cell Volume | m³ | 18 |
| Gravity Concentration | ||
| Type | , | Sepro SB5200 |
| Regrind | ||
| Concentrate Production | % of mill feed | 3.4 |
| Concentrate Regrind Mill Type | , | Vertical |
| Concentrate Regrind Mill Power | kW | 200 |
| Regrind Product P₈₀ | μm | 35 |
| CIL | ||
| Residence Time | hours | 48 |
| Number of Tanks | number | 6 |
| Tank Diameter | m | 6.2 |
| Tank Height | m | 7.8 |
| Carbon Concentration | g/L | 15–20 |
| Cyanide Destruction | ||
| Method | , | SO₂/Air |
| Reagent | , | Na₂S₂O₅ |
| Reagent Addition | kg/t mill feed | 0.6 |
| Final Cyanide Target (WAD) | mg/L | <0.2 |
| Tailings Thickener | ||
| Underflow Density | % | 65 (Table 17-1) / 50 (Section 17.3.7) |
| Thickener Diameter | m | 30 |
Project website: https://spanishmountaingold.com/
Project website: https://spanishmountaingold.com/news/2025/spanish-mountain-gold-provides-project-update-and-announces-2025-exploration-drill-program/
Reagents and Consumables
| Reagent | Consumption (kg/t mill feed) |
|---|---|
| Grinding Media | 0.394 |
| Potassium amyl xanthate (PAX) | 0.065 |
| Methyl isobutyl carbinol (MIBC) | 0.050 |
| Lime | 0.055 |
| Carboxymethylcellulose (CMC) | 0.065 |
| Sodium Cyanide | 0.100 |
| Copper Sulphate | 0.0014 |
| SMBS | 0.022 |
| Sodium Hydroxide | 0.002 |
| Hydrochloric Acid | 0.0003 |
| Leach-Aid | 0.0001 |
| Flocculant | 0.001 |
| Flux (SiO₂ 30% / Borax 40% / Niter 10% / Soda Ash 20%) | 0.001 |
| Carbon | 0.050 |
Technical qualifications
The following limitations apply to the processing information presented in this report:
1. PEA-level design: All process design criteria are based on a Preliminary Economic Assessment level of study, not feasibility-level engineering.
2. No detailed water balance: A detailed plant water balance has not yet been completed.
3. Discrepancies in reported values: The fine ore bin capacity is listed as 10,000 tonnes in the major design criteria table (Table 17-1) but as 20,000 tonnes in the process operating description (Section 17.3.1). Similarly, tailings thickener underflow density is listed as 65% solids in the design criteria and 50% solids in the operating description.
4. Testwork basis: Metallurgical process selection relies on laboratory-scale test work described in Section 13 of the report; no commercial operating data from the Spanish Mountain deposit are provided.
5. Reagent consumption estimates: Reagent consumption values are estimates from the PEA and require confirmation through pilot-scale or demonstration-scale test work.
6. Power consumption: Estimated site power is 10.5 MW with process facilities estimated to use up to 9 MW; these are PEA-level estimates.
Source: *Spanish Mountain Gold Project , 2025 Technical Report*, Section 17: Recovery Methods, pages 179–186.
Consolidated report summaries
The following former standalone pages about this operation were consolidated here on October 25, 2026. They are retained for source traceability; dates and figures reflect each report’s own effective date and may be superseded by the current information above.
Inside Spanish Mountain Gold's 26,000 TPD Processing Circuit: Crushing, Grinding & Flotation
Overview
Nestled in the mineral-rich Cariboo region of British Columbia, Canada, the Spanish Mountain Gold Project represents one of the most significant and advanced-stage gold development projects in North America. Operated by Spanish Mountain Gold Ltd. (TSX-V: SPA), this ambitious venture is poised to become a major producer, targeting an average annual output of over 200,000 ounces of gold over a projected 25-year mine life. Located approximately 70 kilometers northeast of the city of Williams Lake, the project leverages a substantial mineral resource base with a design head grade of 0.46 g/t gold and 0.65 g/t silver. The processing facility, as detailed in the recent NI 43-101 Technical Report and Preliminary Economic Assessment (PEA) dated July 2025, is engineered for a substantial throughput of 26,000 tonnes per day (t/d). This state-of-the-art mineral processing plant incorporates a sophisticated flowsheet designed to maximize recovery through a combination of gravity concentration, flotation, and leaching technologies. The project’s significance extends beyond its economic potential, embodying modern mining principles with a strong emphasis on dry stack tailings management, water recycling, and energy efficiency, setting a new benchmark for sustainable gold mining in Canada.
Key Process Stages
The Spanish Mountain Gold process plant employs a comprehensive and multi-stage circuit designed to efficiently liberate and recover fine gold from a low-grade sulfide ore. The circuit is a testament to modern metallurgical design, integrating conventional technologies with advanced unit operations to optimize recovery and minimize environmental impact.
- Stage 1: Two-Stage Crushing & HPGR Tertiary Grinding: Run-of-Mine (ROM) ore with a top size (F₈₀) of 127 mm is first reduced to a P₈₀ of 37 mm through primary and secondary crushing circuits. The crushed material is then further comminuted by a massive High-Pressure Grinding Roll (HPGR) unit (2.1m x 1.8m, 4100 kW power), which is highly energy-efficient. The HPGR operates with an 80% circulating load and produces a final ball mill feed product with a P₈₀ of just 4 mm.
- Stage 2: Ball Mill Grinding & Classification: The HPGR product is fed to a large ball mill (7.3m diameter x 10.4m effective grinding length, 10,400 kW) operating in closed circuit with a cyclone cluster. This stage grinds the material to a target P₈₀ of 350 µm at a high recirculating load of 350%. The cyclone overflow, at 35% solids, reports to flotation.
- Stage 3: Gravity Concentration & Intensive Leach (GIL): A portion of the cyclone feed is diverted to a gravity circuit featuring four concentrators. This circuit is designed to recover coarse, free gold early in the process, achieving a mass pull of 0.01%. The gravity concentrate is immediately fed to an Intensive Leach Reactor (ILR) for rapid cyanide dissolution, with the resulting pregnant solution sent directly to electrowinning for gold recovery, bypassing the main circuit and boosting overall efficiency.
- Stage 4: Rougher-Cleaner Flotation with Regrinding: The main stream undergoes bulk sulfide flotation using five rougher cells with reagents PAX (collector), CMC (depressant), and MIBC (frother), pulling 11% of the plant feed. The rougher concentrate is reground in two stages: first to a P₈₀ of 45 µm (13.1 kWh/t) and then, after two stages of cleaning, the final concentrate is reground to a ultra-fine P₈₀ of 20 µm (13.8 kWh/t) to liberate locked gold particles.
- Stage 5: Coarse Particle (HydroFloat) Flotation: In a key innovation, rougher flotation tailings are processed in a HydroFloat circuit to recover gold from coarser particles that conventional cells might miss. This step significantly reduces gold losses to tailings, with the HydroFloat tailings representing 44.7% of the plant feed.
- Stage 6: Concentrate Leaching & Carbon Adsorption (CIL): The finely ground flotation concentrate is leached in a six-tank Carbon-in-Leach (CIL) circuit with a total residence time of 24 hours. Sodium cyanide and oxygen are added to dissolve the gold, which is then adsorbed onto activated carbon within the same tanks.
- Stage 7: Carbon Elution, Electrowinning & Doré Production: Loaded carbon is acid-washed, stripped of gold in a pressurized elution column, and regenerated in a kiln for reuse. The gold-rich pregnant eluate is processed in an electrowinning cell to produce a sludge, which is then filtered, smelted with fluxes in a barring furnace, and poured into high-purity gold-silver doré bars.
- Stage 8: Tailings & Water Management: Tailings are meticulously managed. Flotation tailings are thickened and filtered for dry stacking. Leach residue undergoes cyanide destruction with SMBS before being sent to a separate, potentially acid-generating (PAG) tailings storage facility. Water from thickeners is extensively recycled back into the process, minimizing fresh water consumption.
Critical Data
The following table summarizes the key technical and operational parameters that define the scale and efficiency of the Spanish Mountain Gold processing circuit, as outlined in the NI 43-101 report.
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Design Throughput | 26,000 | tpd | Nominal daily processing rate |
| Mill Availability | 91 | % | Grinding & flotation section operational availability |
| Target Grind Size (P₈₀) | 350 | µm | Primary ball mill cyclone overflow size |
| Final Regrind Size (P₈₀) | 20 | µm | Flotation concentrate regrind for leaching |
| Bond Ball Work Index | 16.3 | kWh/t | Ore hardness measure |
| Installed Power (Process Plant) | 36.1 | MW | Total connected load for processing equipment |
| Leach Residence Time | 24 | hours | Total time in CIL circuit |
| Annual Water Consumption (Raw Makeup) | 1.5 | Mm³ | Estimated annual fresh water requirement |
| Annual Sodium Cyanide Consumption | 1,077 | t/a | Primary lixiviant for leaching circuits |
| Mine Life | 25 | Years | Based on current reserves and processing rate |
Additional Interesting Data and Summary
Beyond the impressive throughput and recovery metrics, the Spanish Mountain Gold Project is a case study in modern, responsible mineral processing. The circuit design incorporates several features aimed at reducing its environmental footprint. The use of an HPGR for tertiary crushing is a significant energy-saving choice, as HPGRs are known to be more efficient than traditional crushers and SAG mills for competent ores, directly reducing the project’s power consumption and greenhouse gas emissions. Furthermore, the commitment to filtered, dry stack tailings management is a paramount environmental achievement. This method drastically reduces the footprint of tailings storage, eliminates the need for a large impoundment dam and the associated perpetual water treatment, and greatly improves long-term geotechnical stability. The project plans to seginate tailings based on their geochemical properties, with non-potentially acid generating (non-PAG) material being dry-stacked and a smaller volume of PAG material stored sub-aqueously, demonstrating a sophisticated approach to environmental risk management.
Economically, the project is designed for longevity and efficiency. The 25-year mine life provides significant long-term benefits to the local economy and the region of British Columbia. The estimated annual reagent consumptions, such as 1,784 tonnes of PAX collector and 465 tonnes of MIBC frother, highlight the scale of the operation and its integration into global supply chains. The on-site generation of 93% purity oxygen via a Vacuum Swing Adsorption (VSA) plant is another optimization, ensuring a reliable and cost-effective supply of a critical reagent for the leaching process. The PEA outlines a robust project with compelling economics, positioning Spanish Mountain Gold Ltd. as a future mid-tier gold producer. The comprehensive flowsheet, with its sequential application of gravity, flotation, and leaching, is engineered to achieve maximum recovery from a complex ore body, ensuring that the project will be a technically and environmentally leader in the mining industry for decades to come.
Source: NI 43-101 Technical Report | Preliminary Economic Assessment | Project: Spanish Mountain Gold Project | Date: July 2025
