Spanish Mountain Gold Project — 2025 Technical Report

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

Reagents and Consumables

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.