Toroparu Project — 2025 Technical Report

This technical report for the Toroparu Project in the Cuyuni-Mazaruni Region, Guyana, describes a proposed 7.0 Mtpa processing plant designed to treat oxide and sulphide gold-bearing materials separately through crushing, grinding, gravity concentration, carbon in leach, and sulphide flotation circuits.

Report context

This NI 43-101 Technical Report, a Preliminary Economic Assessment for the Toroparu Project, carries an effective date of October 21, 2025. The report presents a process plant design and flowsheet derived from extensive metallurgical testwork, as described in Section 13 of the original document. The processing strategy is based on industry standard metallurgical practices to treat two primary gold bearing rock types: oxidized saprolite and other near surface oxidized material, and deeper sulphide rock.

Processing route

Primary run of mine handling and crushing

The proposed design specifies that run of mine material, including both oxide and sulphide rock types, will be mined, stockpiled, and processed in separate dedicated campaigns according to the mine plan. Material will be trucked to the process plant and discharged directly onto a 450 kW gyratory crusher for size reduction to a product of P80 150 mm. A water mist dust suppression system will contain dust emissions, and any run of mine material greater than 800 mm will be broken by a rock breaker prior to entering the crusher. An apron feeder will extract the feed from the crusher discharge and feed onto a crusher sacrificial conveyor fitted with an overhead tramp metal magnet. A transfer chute will discharge the feed onto an overland conveyor fitted with a weightometer for metallurgical accounting and sampled for analysis in the metallurgical laboratory.

The crushed feed will be discharged via two parallel streams of vibrating feeders onto the final 45,425 tonne capacity run of mine stockpile, which represents 52.6 hours of storage. When a feed type campaign is concluded, the stockpile pad will be cleaned in preparation for the next feed type campaign.

Grinding circuit

The proposed grinding circuit will comprise a SAG mill operating in closed circuit with a pebble crusher, followed by a ball mill operating in closed circuit with a hydrocyclone cluster. The reclaimed crushed mill feed will be combined with water and fed directly into a 34 foot by 18.25 foot, 12.5 MW, 3,024 tonnes per hour capacity SAG mill. The mill product will pass over a discharge vibrating screen to remove any pebbles greater than 20 mm, which will report to a pebble cone crusher via a feed bin. The crushed pebbles will then report back to the mill feed conveyor. A pebble stockpile will be located next to the pebble crusher allowing the pebbles to be reclaimed directly from the stockpile and fed back onto the pebble crusher discharge conveyor in the event of a crusher shut down.

The 3,023.6 tonnes per hour grinding mill product of minus 20 mm will report to a cyclone feed hopper then pumped to a cyclone classifying cluster with an overflow P80 of 75 microns. The plus 75 micron underflow will be split into two streams. An amount equivalent to the fresh feed rate of 863.9 tonnes per hour will discharge onto a gravity scalping vibrating screen with 2 mm aperture panels, from where the plus 2 mm feed will be sent to the ball mill and the minus 2 mm feed will report to the gravity recovery circuit. The remaining 1,295.8 tonnes per hour split will report directly to the 26 ft by 42.5 ft, 18 MW ball mill. The ball mill discharge will be fitted with a trommel with 12 mm apertures, and any oversize material will report to the scats bin for disposal. The undersize material will be discharged onto the cyclone feed hopper.

The classifying cyclones overflow will pass over a single deck vibrating trash screen with 500 micron aperture screen panels. Any oversize material will be collected in a trash bin for disposal and the undersize will report to a high rate pre-leach primary thickener, with the underflow reporting to the sulphide flotation circuit when processing sulphide mill feed and to the carbon in leach circuit when processing oxide mill feed.

Gravity concentration and intensive leach circuit

In the proposed design, slurry from the cyclone cluster feed hopper will be pumped to the classifying cyclone with the plus 75 micron underflow reporting to the scalping screen fitted with 2 mm apertures. The minus 2 mm material will report to two Knelson gravity gold concentrators operating in parallel. The resulting gravity concentrate stream from the gravity concentration circuit will be pumped to the intensive cyanide leach circuit and the tailings stream will be detoxified prior to being sent back to the cyclone classification cluster for further liberation in the ball mill.

At the intensive cyanide leach circuit, 36.7 kg/t of sodium cyanide will be added with oxidant to the gravity concentrate to commence the gold leaching reaction in a horizontal drum leach reactor. The report states that 5 kg/t of lime will be added to maintain the slurry pH at 10 and 71 kg/t of flocculant will be added to facilitate the removal of particulates from the loaded solution.

The pregnant gold leach solution will be pumped to a dedicated intensive cyanide leach pregnant solution tank from where the solution will be transferred to the electrowinning circuit. The leached solid residue will be neutralized by the addition of hydrogen peroxide in an agitated tank to prevent cyanide from reporting to the flotation circuit, before being pumped back to the ball mill circuit for further grinding.

In the secure gold room, the pregnant solution from the intensive cyanide leach and carbon in leach process will be plated out on to separate dedicated electrowinning cell cathodes operating on a single pass basis to produce a gold sludge. The cathodes will be transferred from the cells to the cathode washing tank where a high pressure washer will be used to dislodge the gold sludge from the cathode surface. The barren solution will be collected in the barren solution tank then pumped back to the carbon in leach circuit.

The gold sludge will be filtered in a plate and frame filter press to produce cake gold, then dried in an oven, mixed with fluxes, and fired in a furnace to produce doré. The doré will be cleaned, sampled, and transferred to a safe for safekeeping prior to transport to the refinery.

Pre-leach thickening circuit

The proposed cyclone overflow from the ball mill, at 864 tonnes per hour equivalent to the fresh feed, will be transferred to the primary thickener feed box which will direct the feed to a high rate thickener together with flocculant to aid the solids settling rate. When processing sulphide material, the thickened underflow slurry will be pumped to the agitated sulphide rougher conditioning tank in the rougher flotation circuit. When processing oxide material, the underflow will be pumped directly to the carbon in leach circuit.

Carbon in leach circuit

The proposed design specifies that oxide and sulphide mill feed will be separately processed in the hybrid carbon in leach circuit with the first tank in the eight tank train operating solely as a leach tank. The carbon in leach circuit will comprise eight cascading agitated adsorption tanks for 48 hours of leaching time. The first tank provides elevated solution grades and activated carbon loads, resulting in a reduced elution capacity demand. The pH will be maintained at 10.2 with lime, and 1.05 kg/t of sodium cyanide will be dosed into the first tank to dissolve the gold and silver in the slurry. The slurry will then pass sequentially through the remaining seven tanks, each of which contains activated carbon. Adsorption will occur in a counter-current configuration with fresh carbon entering at tank 8 and advanced upstream by transfer pumps toward tank 2.

After adsorption, the slurry will be discharged onto a carbon in leach tailings screen ensuring that any stray carbon is captured in the oversize and returned to the circuit. The carbon free screen undersize will be pumped to the detoxification circuit for cyanide destruction before being pumped to the tailings management facility.

The Anglo American Research Laboratories elution method was selected. The loaded carbon from the first adsorption tank will be sent for acid washing via the loaded carbon screen, with the underflow slurry transferred to the tailings screen of the leach circuit while the carbon from the screen oversize gravitates to a single acid wash column. The elution circuit will use a cold sodium cyanide soak to prepare the carbon and load the solution with free cyanide, followed by a steady state eluting phase to desorb the gold and silver from the carbon.

Following elution, the barren carbon will be thermally reactivated in a 2.9 MW rotary kiln to restore its adsorption capacity, stored in a product hopper, then reintroduced into the leach circuit in the final adsorption stage.

The Inco SO2/air process will be used for tailings cyanide detoxification. The solid residue remaining from the carbon in the leach circuit will be directed over a carbon safety screen to remove carbon then directed to the detoxification circuit comprising three tanks operating in series with a residence time of 82.5 minutes with sodium metabisulfite, copper sulphate, lime, dilution water, air, and lime. The detoxified slurry with an expected CN WAD of 0.07 mg per litre, below the required discharge limits, will be pumped to the tailings management facility.

Flotation circuit

The proposed design specifies that when processing oxide mill feed, the 864 tonnes per hour pre-leach thickener underflow will be pumped directly to the carbon in leach circuit. When processing sulphide mill feed, the underflow will be pumped to the sulphide rougher flotation conditioning tank where two collectors, a frothing agent, lime slurry, and process water will be added and pumped to six rougher flotation cells for a 40 minute residence time. The rougher concentrate collected from the flotation cells will gravitate to a sulphide sump where a froth pump will deliver the slurry to the sulphide regrind mill cyclone feed tank via a sampler. A cyclone cluster of 14 units and 1 standby unit will operate in a closed circuit with a single 1.5 MW regrind mill.

The reground flotation rougher concentrate will report to four cleaner flotation cells for a 20 minute residence time at a pH of 11 with sulphide thickener overflow process water, sulphide cleaner tailings, and cleaner flotation reagents. The cleaner concentrate will be pumped via froth pumps to four recleaner flotation cells for a 20 minute residence time at a pH of 11 with the recleaner tails and recleaner flotation reagents.

The recleaner tails will be recycled back to the cleaner circuit and the concentrate will be pumped via froth pumps to a single Jameson recleaner flotation cell at a pH of 11 with recleaner flotation reagents.

The copper sulphide concentrate will be dewatered in a high rate thickener with an underflow solids density of 55%. The slurry will be pumped to either of two horizontal plate filter presses, including one standby, to reduce the moisture to 10%. The filter cake will then be transferred to a storage bin with a 7 day production capacity.

The report notes that mineralogical analysis of the copper concentrates from the Toroparu deposit identified the presence of deleterious elements such as bismuth, selenium, tellurium, and arsenic, which may result in smelter penalties.

Key reported parameters

Technical qualifications

This report is a Preliminary Economic Assessment and is not considered to be a feasibility study. The process plant design criteria and flowsheet are based on extensive metallurgical testwork as described in Section 13, but the report provides specific recommendations for additional work, including detailed mineralogical and liberation studies, comminution and material characterization tests, gravity and intensive leach testwork, flotation testwork in both open circuit and locked cycle modes, leaching studies including both bottle roll and tank leach tests, detoxification testwork, settling and flocculation testwork, and water quality assessment. The report notes that all testwork should be conducted at a single accredited laboratory to ensure consistency and comparability of results.

Source: NI 43-101 Technical Report Preliminary Economic Assessment for the Toroparu Project, Cuyuni-Mazaruni Region, Guyana, effective date October 21, 2025, Sections 17.1 through 17.8.