Hammerdown Gold Recovery: Flotation-Leach & Merrill Crowe

Source: New Found Gold Corp (2026)
Website: https://newfoundgold.ca/

Critical Data

Overview

New Found Gold Corp.’s Hammerdown Gold Project in Newfoundland & Labrador, Canada, employs a comprehensive gold recovery flowsheet integrating crushing, ore sorting, flotation, cyanidation, and Merrill Crowe precipitation. The Pine Cove process plant, operational since 2012 and recommissioned in 2025 after a care-and-maintenance period, treats material from the Hammerdown deposit. A proposed three-stage crushing and XRT sorting facility at the Hammerdown mine site will reject approximately 47% of sorter feed as waste, upgrading the mill feed grade and reducing downstream processing volume. Sorted material is hauled to Pine Cove, where a single-stage ball mill grinds to a P80 of 125 µm for flotation. A rougher-cleaner flotation circuit produces a gold-pyrite concentrate at 7–8% mass pull, which is thickened, reground to <20 µm, and leached via cyanidation for 72 hours. Gold is recovered from the pregnant solution using the Merrill Crowe process, producing doré bars. Leach residues undergo SO₂/air cyanide destruction before combined flotation and detox tailings are pumped to an in-pit tailings storage facility. The overall average gold recovery from the sorting and processing circuit reaches 93.1%, with the crusher-sorter handling 1,200 t/d and the Pine Cove plant processing a nominal 700 t/d. This integrated approach maximizes resource utilization and economic returns for the Hammerdown project.

Key Process Stages

• Stage 1: Crushing and Ore Sorting at Hammerdown – Run-of-mine material undergoes three-stage crushing (jaw, secondary cone, tertiary cone) with intermediate screening. A triple-deck vibrating screen separates material into three fractions: +35–60 mm and +10–35 mm feed two XRT ore sorters, while -10 mm fines bypass sorting. The sorters reject approximately 47% of the feed as waste, achieving an average gold recovery of 92.5% in the sorted product. The final crushed product has a P80 of 7.7 mm and is trucked to the Pine Cove plant.
• Stage 2: Primary Grinding – Crushed material (F80 ~10 mm) is fed to a 3.2 m dia x 4.27 m EGL Marcy ball mill with a 597 kW (800 hp) motor. Process water is added to maintain 75% w/w discharge density. Mill discharge is classified by a 400CVX10 Cavex cyclone in closed circuit, producing a cyclone overflow with P80 of 125 µm for flotation feed.
• Stage 3: Flotation and Concentrate Regrind – Cyclone overflow reports to a rougher-cleaner flotation circuit comprising three rougher, one cleaner, and one scavenger column cells. PAX and PolyFloat 3330 are collectors, MIBC is frother. The gold-pyrite concentrate (7–8% mass pull) is thickened in a 7.6 m diameter thickener, then reground in a 2.2 m dia x 3.3 m EGL ball mill (185 kW) to P80 <20 µm to liberate gold minerals.
• Stage 4: Cyanidation and Dewatering – Reground concentrate slurry enters a pre-aeration tank followed by three mechanically agitated leach tanks. Sodium cyanide (pH 10.5–11) and compressed air are added; leach residence time is approximately 72 hours. Leach slurry is dewatered via two drum filters (2.43 m dia x 3.1 m). Pregnant solution is sent to Merrill Crowe; tailings residue goes to detoxification.
• Stage 5: Gold Recovery and Detoxification – Pregnant solution is clarified in leaf filters, de-aerated in a vacuum tower, then treated with zinc dust to precipitate gold. Precipitates are collected in plate-and-frame filter presses, dried, and smelted in an induction furnace with fluxes to produce gold doré and slag. Leach tailings are detoxified in two agitated tanks using SO₂/air (SMBS and copper sulphate catalyst), then combined with flotation tailings and pumped to an in-pit tailings storage facility.

Additional Interesting Data and Summary

The Hammerdown Gold Project’s recovery methods are designed to efficiently process variable-grade ore while minimizing waste and operating costs. Key technical metrics include a sorting circuit that rejects 47% of the feed mass while retaining 92.5% of the gold, resulting in a final product stream of 700 t/d at an upgraded grade. The XRT sorters operate on two size fractions (+35–60 mm and +10–35 mm) and achieve a mass pull of 53% per machine. The Pine Cove plant’s flotation circuit achieves a concentrate mass pull of 7–8%, which is then reground to less than 20 µm for optimal cyanide leaching. Leaching occurs over 72 hours in three agitated tanks, with cyanide maintained at pH 10.5–11 using sodium hydroxide. Gold recovery via Merrill Crowe involves clarification, de-aeration, zinc precipitation, and smelting to produce doré bars. Environmental management includes a SO₂/air cyanide destruction circuit for leach tailings and in-pit tailings storage for both flotation and detoxified tailings. Water consumption is estimated at 98,000 m³ annually, largely sourced from tailings reclaim, minimizing freshwater demand. The process plant uses electrical power from the local grid and propane for heating. The project benefits from existing infrastructure at Pine Cove, which operated from 2012 to 2022 before a brief care-and-maintenance period and recommissioning in 2025. The integration of ore sorting at Hammerdown significantly reduces the volume of material trucked to the mill, lowering haulage costs and carbon footprint. Future outlook includes potential expansion of throughput based on resource growth and optimization of sorter rejection rates to further enhance feed grade. The overall recovery of 93.1% confirms the technical viability of the flowsheet, positioning the Hammerdown Gold Project as a robust, low-risk development with strong economic fundamentals.

Key Processes: Flotation, Cyanidation, Gravity Separation, Ball Mill, Crushing

Target Commodities: Gold, Copper, Zinc, Lead