La Mina Gold-Copper Project: 15,000 tpd Flotation and CIL Circuit

GoldMining Inc.'s La Mina project in Antioquia, Colombia would process ore through a conventional crushing, grinding, and flotation circuit, with cyanide leaching of flotation tailings to recover gold and silver.

The La Mina Gold-Copper Project is located in the Department of Antioquia in the Republic of Colombia, South America, approximately 51 km southwest of Medellín. GoldMining Inc. owns 100% of the project through its wholly owned subsidiary Bellhaven Copper & Gold Inc. The property consists of two concessions covering approximately 3,208 hectares. The project is a development-stage asset: GoldMining announced the updated Preliminary Economic Assessment on April 28, 2026, and filed the supporting technical report on June 8, 2026. The technical report has an effective date of April 22, 2026. The PEA contemplates a conventional open pit, truck and shovel operation feeding a 15,000 tpd processing plant that produces a copper concentrate and gold-silver doré. The mineral resource estimate includes Indicated resources of 33.8 million tonnes grading 0.73 g/t gold, 2.08 g/t silver, and 0.21% copper, plus Inferred resources of 56.2 million tonnes grading 0.58 g/t gold, 2.32 g/t silver, and 0.14% copper. No mineral reserves have been estimated. The report states the PEA is preliminary in nature, and there is no certainty that the reported results will be realized.

Critical Data

Project status and study basis

La Mina is not an operating mine. GoldMining’s April 2026 PEA evaluates a proposed open-pit operation processing 15,000 tpd over a projected 11.2-year mine life. The study estimates average metallurgical recoveries of 91% for gold, 80% for copper, and 64% for silver. These are PEA projections, not demonstrated plant performance. The study includes Inferred Mineral Resources and does not declare Mineral Reserves, so its production and economic outcomes remain preliminary.

Overview

The La Mina processing plant is designed around a conventional crushing and grinding circuit followed by copper flotation. Gold and silver are recovered as by-products in the copper concentrate, and additional gold is recovered from flotation tailings through cyanide leaching in a carbon in leach circuit. The flowsheet then includes cyanide detoxification before tailings are sent to a lined storage facility.

Mineralized material from the La Cantera, La Garrucha, and Middle Zone open pits will be processed at 15,000 tonnes per day. The plant is planned to operate 24 hours per day with overall circuit availability of 92%. The process department is expected to have 128 employees.

The processing route begins with primary crushing and coarse stockpiling, moves through a SAG mill and ball mill grinding circuit, then flotation with a regrind stage and two cleaning stages. Final flotation tailing reports to pre-aeration tanks and then to a CIL circuit. Pregnant carbon is stripped and reactivated, and the gold and silver are recovered by electrowinning and refined into doré bars. CIL tailings go through cyanide detoxification before being deposited in the tailings storage facility.

Key Process Stages

Crushing begins with haul trucks from the open pits depositing run of mine material into a gyratory crusher feed hopper. Gyratory crusher product is conveyed to a cone crusher for secondary size reduction. The crushed rock is reduced to a nominal 38 mm 80% passing size and discharged onto a crushed material stockpile.

The grinding circuit receives crushed material from the stockpile at a controlled feed rate. A 9.8 m diameter by 3 m long 5.0 MW SAG mill operates in open circuit. SAG mill product discharges to a vibrating screen, with oversize conveyed to one of two pebble crushers operating in parallel. Pebble crusher product returns to the SAG mill. Screen undersize material reports to the cyclone feed pump sump, where dilution water is added. Slurry is pumped to a cyclone cluster. Cyclone underflow flows by gravity to the ball mill feed chute. The ball mill, measuring 5.8 m diameter by 12.0 m long with 8.0 MW power, operates in closed circuit with the hydrocyclones. Ball mill product discharges to the cyclone feed pump sump and along with SAG mill discharge is pumped to the cyclone cluster. Cyclone overflow slurry at approximately 35% solids by weight flows by gravity to the first rougher flotation conditioning tank. Lime is added as required to the cyclone feed pump sump to adjust slurry pH for flotation. Grinding media additions are based on power factor set points, which are periodically adjusted to compensate for liner wear.

Flotation begins with cyclone overflow reporting to the first of two conditioning tanks operating in series. Collector and frother are added, and the conditioned slurry is pumped to a bank of eight 120 m³ rougher flotation cells. Frother and collector may also be added to individual cells as necessary. Electric blowers supply flotation air. Rougher tailings report to the first of two scavenger conditioning tanks, also in series, where more collector and frother are added. The conditioned slurry is pumped to a bank of eight 120 m³ scavenger flotation cells. Rougher concentrate, approximately 8% to 12% of the flotation feed dry weight, combines with scavenger concentrate and is pumped to a cyclone cluster. Cyclone overflow reports to the first cleaner conditioning tank, while underflow goes to a 4 m diameter by 7.5 m long 1,675 kW regrind ball mill that grinds to a nominal 30 µm to further liberate valuable minerals. Scavenger tailing slurry goes to a final flotation tailing thickener.

The cleaner circuit uses a single conditioning tank with collector and frother additions. Lime is introduced to achieve a pH of 11.0, which depresses pyrite. Conditioned slurry feeds a bank of two 30 m³ first cleaner flotation cells. First cleaner concentrate feeds a second cleaner stage of two flotation columns operating in parallel. Second cleaner concentrate, at approximately 23% copper, 75.8 g/t gold, and 144.2 g/t silver, is pumped to the concentrate dewatering thickener. First and second cleaner tailing products go to cleaner scavenger flotation consisting of two 30 m³ cells in series. Cleaner scavenger concentrate is pumped to the regrind mill cyclone cluster, while tailing product goes to the first rougher conditioning tank.

Copper concentrate dewatering begins with thickening. Thickener overflow reports to a process makeup water tank. Underflow is pumped to a pressure filter feed holding tank, then to one of two pressure filters operating in parallel. Concentrate is dewatered to roughly 8% moisture by weight and deposited in a concentrate storage area, where it is loaded into trucks for shipment to a third-party smelter. Filtrate is pumped to the process makeup water tank.

Pre-aeration and cyanide leach treat the scavenger flotation tailings. Scavenger tailing is pumped to a high-rate thickener, with overflow going to the process makeup water tank. Underflow slurry at approximately 45% to 48% solids by weight reports to the first of two 19 m diameter by 19 m high agitated pre-aeration tanks operating in series. Compressed air oxidizes sulfide minerals, reducing sodium cyanide consumption and gold dissolution time. Total pre-aeration residence time is roughly twelve hours. The pre-aerated slurry is pumped to a train of eight 19 m diameter by 19 m high agitated CIL tanks operating in series. Each tank contains activated coconut shell carbon at a concentration of 35 grams per liter of solution. Activated carbon is pumped upstream counter-current to the leach slurry flow. Sodium cyanide and milk of lime are added to the CIL tanks to maintain optimum cyanide concentration and pH. Compressed air addition provides oxygen levels for the gold dissolution reaction. Dissolved gold and silver adsorb onto the activated carbon surfaces. CIL residence time is in the 48 hour range.

Carbon stripping and reactivation begins with loaded carbon pumped from the first CIL tank to one of two acid wash tanks operating in parallel, where scale is removed from carbon surfaces. Carbon is then transferred to one of two strip vessels operating in parallel. Caustic solution is added to increase pH to alkaline levels. Pressurized hot alkaline solution circulates through the strip vessels and electrowinning cells, where gold and silver in solution plate onto steel wool cathodes. Stripped carbon is thermally reactivated in a rotary kiln, then passed over a vibratory screen to remove fine particles. Reactivated and screened carbon is transferred to the last tank of the CIL train.

Refining starts with electrowinning cell sludge manually washed from the loaded steel wool cathodes. The sludge is dried, then melted in a single sludge melt furnace. The molten gold and silver-bearing product is poured into doré bar molds. Doré bars are sent to a third-party refinery for final purification.

Tailing treatment begins with CIL tailing slurry pumped to the first of two 19 m diameter by 19 m high agitated cyanide detoxification tanks operating in parallel. Residual cyanide levels are reduced to acceptable limits. Detox retention time is approximately twelve hours. Detoxified tailing slurry is sent to the lined tailings storage facility.

Additional Interesting Data and Summary

The process plant relies on a range of reagents including flotation collector, frother, milk-of-lime, flocculant, anti-scalant, sodium cyanide, and cyanide detox reagent. Process service systems include fresh water supply, process water made up largely of recycled water from the TSF and from in-plant processes, potable water, fire suppression water, flotation plant blowers, pre-aeration/CIL/cyanide detoxification reaction compressors, and services and instrument air compressors.

The flowsheet uses a SAG mill with pebble crushing in open circuit, followed by a ball mill in closed circuit with hydrocyclones. Flotation includes rougher, scavenger, regrind, and two cleaning stages with columns, plus a cleaner scavenger stage. The CIL circuit follows flotation tailings thickening and pre-aeration. Carbon is stripped, reactivated, and returned to the circuit. Electrowinning and furnace refining produce doré bars. Tailings are detoxified before deposition in a lined facility.

The processing design is described at a PEA level, and the report recommends further work including locked-cycle flotation and variability testing, along with expanded metallurgical test work. The report also notes that the mineral resource estimate used for the PEA includes Inferred Mineral Resources, which are considered too speculative geologically to have economic considerations applied that would enable categorization as Mineral Reserves.

Study history

• 2016 resource report: Bellhaven Copper & Gold documented the La Cantera and Middle Zone resource models and recommended further work, including evaluation of La Garrucha.
• 2021 technical report: GoldMining updated the resource review and identified sufficient information to advance a PEA.
• 2023 PEA: the project basis advanced to a 15,000 tpd open-pit and flotation-plus-leach concept incorporating La Cantera, Middle Zone, and La Garrucha.
• 2026 updated PEA: GoldMining retained the 15,000 tpd flowsheet, updated the resource and economic assumptions, and reported 91% gold, 80% copper, and 64% silver recovery over a projected 11.2-year mine life.

Technical report library and primary sources

• GoldMining: La Mina project and current resource statement
• April 28, 2026 updated PEA announcement (EDGAR)
• June 8, 2026 technical-report filing announcement (EDGAR)
• July 24, 2023 updated PEA announcement

Key Processes

• Gyratory crushing followed by cone crushing to 38 mm 80% passing
• SAG mill in open circuit with pebble crushers, then ball mill in closed circuit with hydrocyclones
• Copper flotation with rougher, scavenger, regrind, first cleaner, second cleaner columns, and cleaner scavenger stages
• Concentrate thickening and pressure filtration to 8% moisture for smelter shipment
• Pre-aeration of flotation tailings for twelve hours to oxidize sulfides
• Cyanide leaching in eight CIL tanks with 48-hour residence time using coconut shell carbon
• Carbon stripping with hot alkaline solution, electrowinning onto steel wool cathodes, and thermal reactivation
• Sludge melting and doré bar production for third-party refining
• Cyanide detoxification in agitated tanks with twelve-hour retention before tailings deposition
• Reagent systems for flotation collector, frother, milk-of-lime, flocculant, anti-scalant, sodium cyanide, and cyanide detox reagent

Source: Technical Report and Preliminary Economic Assessment for the La Mina Gold-Copper Mineral Deposit, Antioquia, Republic of Colombia, April 22, 2026. Project website: La Mina