Hat Project Cu-Au Recovery: Flotation, Grinding & Hydromet

Source: Doubleview Gold Corp (2026)
Website: https://www.doubleview.ca/hat-project/

Critical Data

Overview

Doubleview Gold Corp. is developing the Hat Project, a copper-gold porphyry deposit located in northwest British Columbia, Canada. The April 2026 Preliminary Economic Assessment (PEA) outlines a state-of-the-art recovery facility designed to treat 120,000 tonnes per day of open-pit ore over a 25-year mine life. The proposed concentrator employs conventional crushing, grinding, and flotation methods to produce a high-grade copper concentrate with payable gold, silver, and cobalt credits. Three processing scenarios are evaluated: Scenario A1 uses conservative metallurgical recoveries derived from early-stage testwork; Scenario A2 applies improved copper and gold recoveries expected after further optimization; and Scenario B adds a downstream hydrometallurgical circuit to recover cobalt, gold, silver, and scandium from a pyrite-cobalt concentrate. The flowsheet consists of two identical processing lines each with primary gyratory crushing, SAG and ball mill grinding to a P80 of 75 µm, copper-gold rougher and cleaner flotation, and concentrate dewatering. Scenario B incorporates a separate pyrite-cobalt flotation circuit, roasting, and acid leaching for scandium extraction. This integrated approach maximizes value recovery while allowing staged development—hydrometallurgical commissioning is planned for Year 3. The PEA emphasizes that further metallurgical optimization and pilot-scale testing will refine equipment sizing and recovery assumptions, but the overall treatment strategy is expected to remain unchanged. The Hat Project’s recovery methods represent a robust combination of proven technologies tailored to the deposit’s unique mineralogy, positioning it as a significant copper-gold producer in the region.

Key Process Stages

• Stage 1: Primary Crushing — Run-of-mine ore is fed to a gyratory crusher (model KM60-89 or similar) via a static grizzly with 1.4 m x 1.4 m openings. A rock breaker handles oversize material. The crusher reduces ore to a P80 of 140 mm at a total rate of 7,143 t/h (3,571 t/h per line). Crushed material is conveyed to a covered stockpile with 60,000 tonnes live capacity per line, providing surge capacity for downstream grinding.
• Stage 2: Grinding and Classification — Each of two processing lines includes one SAG mill (12.2 m diameter x 6.7 m long) and two ball mills (8.6 m diameter x 12.2 m long) in closed circuit with cyclones. The SAG mill reduces feed to a P80 of 1,400 µm, and the ball mills further grind to a final product P80 of 75 µm with a circulating load of 300%. Total milling rate is 5,435 t/h (2,717 t/h per line). Grinding is conducted wet at approximately 34% solids, with lime addition for pH control.
• Stage 3: Copper-Gold Rougher and Cleaner Flotation — Conditioned slurry (pH 10.5–11.0) enters a rougher flotation circuit of four 600 m³ tank cells per line. Reagents include lime, sodium cyanide (pyrite depressant), collectors SIPX and A3477, and frother MIBC. The rougher concentrate (~10% mass pull) is reground to P80 30 µm using an IsaMill or similar, then cleaned in two stages (100 m³ cells). Final concentrate targets 25% Cu with payable gold. Provision for a third cleaner column cell is included, pending testwork.
• Stage 4: Cobalt-Pyrite Flotation (Scenario B only) — Rougher tailings from the copper-gold circuit are conditioned at pH 6.7 with sulphuric acid, copper sulphate activator, collector PAX, and frother MIBC. The circuit mirrors the copper-gold configuration with four 600 m³ rougher cells, regrind to P80 30 µm, and two cleaning stages. The resulting cobalt-pyrite concentrate is thickened and filtered before being fed to the downstream hydrometallurgical roaster.
• Stage 5: Tailings Management and Hydrometallurgical Recovery (Scenario B) — Final flotation tailings are thickened; a portion is diverted to the scandium recovery plant. The cobalt-pyrite concentrate is roasted to produce sulphuric acid and a calcine. Acid is used to leach tailings for scandium recovery (72% Sc recovery), while the calcine undergoes hydrometallurgical processing to recover cobalt (78% Co), gold (89% Au), and silver (68% Ag). Tailings not used for scandium are deposited in a tailings storage facility with water recycled to the process.

Additional Interesting Data and Summary

The Hat Project’s recovery design is underpinned by preliminary metallurgical testwork conducted at Sepro Laboratories in Langley, B.C., using bench-scale flotation and characterisation studies. Although no locked-cycle or pilot-scale testing has been completed, the PEA assumes conservative recoveries for Scenario A1—80% Cu, 66% Au, 53% Ag, and 30% Co—while Scenario A2 targets improved performance (89% Cu, 75% Au) through further optimisation. Scenario B elevates gold recovery to 89% and cobalt to 78% by incorporating the hydrometallurgical circuit. The concentrator is designed for 92% grinding and flotation availability and 70% crusher availability, with spare capacity built into equipment selection. Environmental considerations include a covered ore stockpile and dust collection system at crushing and reclaim points, plus a comprehensive water management strategy that recycles thickener overflow and tailings pond return water to minimise fresh water consumption. The tailings storage facility is designed to allow controlled deposition and water reuse, with a portion of tailings diverted for scandium recovery in Scenario B, reducing waste volume. Economically, the staged development—commissioning the hydrometallurgical circuit in Year 3—allows capital deferral while maximising by-product revenue from cobalt, scandium, and additional gold and silver. Sustainability initiatives include the potential for gravity gold recovery (subject to testwork) and the use of sulphuric acid from roasting to avoid external acid purchases, lowering the carbon footprint. Future work will focus on locked-cycle flotation tests, pilot-scale grinding and flotation campaigns, and detailed engineering of the SAG and ball mills, which remain conceptual at this stage. The flowsheet’s flexibility to accommodate three processing scenarios reflects the project’s robust technical foundation and positions the Hat Project as a significant future supplier of copper, gold, cobalt, and scandium in a region with established mining infrastructure. As the PEA progresses to pre-feasibility, additional data will refine equipment sizes, recoveries, and operating costs, but the core recovery methods—crushing, grinding, flotation, and hydrometallurgy—are expected to remain central to the project’s development.

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

Target Commodities: Gold, Silver, Copper