Whistler Gold-Copper Project: 40,000 t/d Flotation & Leaching Recovery

Source: GoldMining Inc (2026)
Website: https://www.usgoldmining.us/project/whistler-gold-project/

Critical Data

Overview

The Whistler Gold-Copper Project, operated by GoldMining Inc. and U.S. GoldMining Inc., is a large-scale mining development located in Alaska, USA. The project’s process plant is designed to treat 40,000 tonnes per day of mineralized material from the Whistler gold-copper porphyry deposit, employing a combination of froth flotation and gold leaching to produce high-grade copper concentrate and gold doré over a 14.6-year mine life. Based on preliminary metallurgical testing and economic modelling, the plant leverages conventional technologies widely used in similar operations. The significance of the Whistler Project lies in its robust overall gold recovery of 88.9% and copper recovery of 77.8%, achieved through an integrated flowsheet that includes primary and secondary crushing, high-pressure grinding rolls (HPGR), ball milling, copper flotation with regrind and three-stage cleaning, cyanide leaching with carbon-in-pulp (CIP) adsorption, and AngloAmerican Research Laboratories (AARL) carbon stripping for gold recovery. The process design emphasizes operational efficiency, environmental responsibility through cyanide destruction using the INCO sulfur dioxide/air process, and water recovery via tailings thickening. The effective date of the technical report is March 2, 2026, marking a key milestone for the project. This article details the recovery methods that make the Whistler Gold-Copper Project a technically sound and economically attractive venture.

Key Process Stages

• Stage 1: Crushing – Run-of-mine material (F80 635 mm) is fed into a primary gyratory crusher (600 kW) operating in open circuit, producing a P80 of 136 mm. Crushed material is conveyed to a 21,750 t stockpile providing 12 hours of live capacity. Reclaimed material undergoes secondary crushing via three cone crushers (2 duty, 1 standby, each 671 kW) in closed circuit with double-deck vibrating screens (top deck 90 mm, bottom deck 60 mm), generating a final crushed product P80 of 41 mm.
• Stage 2: Grinding – Crushed ore feeds an HPGR (8,700 kW) in closed circuit with vibrating screens (15 mm top, 5 mm bottom) to produce a P80 of 3.25 mm. HPGR product then enters two parallel ball mills (each 18,100 kW, 8.53 m dia. x 12.50 m EGL) in closed circuit with cyclone clusters at 350% circulating load. Cyclone overflow achieves a target P80 of 120 μm, with slurry density maintained at 60% solids using slaked lime and process water.
• Stage 3: Copper Flotation – Cyclone overflow feeds a rougher flotation bank of five forced-air mechanical cells (500 m³ each) with frother and collector addition. Rougher concentrate is reground in two parallel stirred mills (each 3,800 kW) to a P80 of 15 μm, then cleaned through three stages: Cleaner 1 (4 x 37 m³ cells), Cleaner 2 (3 x 6 m³ cells), and Cleaner 3 (2 x 6 m³ cells). Final concentrate grades 25% Cu with copper recovery of 78.1%.
• Stage 4: Gold Leaching – Rougher flotation tailings are thickened in a 61 m high-rate thickener to 48% solids, then leached with sodium cyanide and slaked lime in two parallel trains of eight tanks each (8,600 m³ per tank) for 48 hours residence time. Leach discharge proceeds to two parallel trains of six CIP adsorption tanks (1,400 m³ each, 6 hours residence time). Gold leach extraction is 74.9% with silver extraction at 20.5%.
• Stage 5: Gold Recovery and Cyanide Destruction – Loaded carbon from CIP undergoes acid washing (3% HCl) and cold cyanide wash (2% NaCN/2% NaOH) in an AARL column system (15 t capacity). Gold is stripped at 90°C, electrowon, filtered, and smelted into doré bars (95% gold recovery). Barren carbon is regenerated at 750°C in a rotary kiln. Tailings from CIP are treated in two parallel tanks (3,310 m³ each, 120 min) using the INCO SO₂/air method to reduce CNWAD from 200 mg/L to <5.0 mg/L, then thickened (73 m thickener) to 60% solids for disposal.

Additional Interesting Data and Summary

The Whistler Gold-Copper Project’s recovery methods are supported by comprehensive design criteria that drive efficiency and sustainability. The comminution circuit relies on a Bond ball mill work index of 22.2 kWh/t (75th percentile) and an abrasion index of 0.130 g, with HPGR achieving a 100% circulating load. The crushing circuit operates at 75% availability for primary crushing and 92% for secondary, grinding, and flotation, ensuring high utilization. Flotation residence times incorporate a 2.5x scale-up factor from laboratory tests: rougher at 30 minutes, Cleaner 1 at 12.5 minutes, Cleaner 2 at 7.5 minutes, and Cleaner 3 at 5 minutes. Copper concentrate handling includes a high-rate thickener (11 m diameter, 0.2 t/m²/h) and a pressure filter producing 8% moisture cake with 260 kg/m²/h filtration rate. The gold leaching circuit uses 0.5 kg/t NaCN and 1.4 kg/t lime, with 48-hour leach and 6-hour CIP adsorption. Cyanide destruction targets a CNWAD concentration of 1.0 mg/L using 5 g SO₂/g CNWAD, managed through two 3,310 m³ tanks with 120-minute residence. Tailings thickening uses a 73 m diameter thickener at 0.7 t/m²/h, recovering water for recycle. Environmental considerations are integrated: the INCO process effectively detoxifies tailings, and high-rate thickeners minimize water loss. The economic impact is substantial—production of a 25% Cu copper concentrate and gold doré over a 14.6-year mine life creates long-term value. Sustainability initiatives include HPGR energy efficiency (reducing overall comminution power), water recovery (thickener overflow recycled), and use of conventional reagents (lime, flocculant, cyanide) with strict containment. Future outlook indicates potential optimization through advanced process control and possible expansion, leveraging the established flowsheet. The Whistler Project stands as a technically robust example of modern gold-copper recovery, combining proven flotation and cyanidation technologies with high environmental standards.

Key Processes: Flotation, CIP/CIL, Cyanidation, Gravity Separation, Ball Mill, Crushing

Target Commodities: Gold, Silver, Copper