Gravity-CIL Gold Recovery at Equinox’s Valentine Mine

Source: Equinox Gold Corp (2026)
Website: https://www.equinoxgold.com/our-mines/valentine/

Critical Data

Overview

Equinox Gold Corp.’s Valentine Gold Mine in Newfoundland and Labrador, Canada, employs a proven conventional gravity and cyanidation flowsheet to recover gold from run-of-mine ore. The process plant, which achieved first gold pour on September 15, 2025, and commercial production on November 18, 2025, is designed to nominally treat 2.5 Mt/a of ore with an overall gold recovery of 93%. Key to this performance is a two-stage grinding circuit (SAG and ball mills), a gravity concentration circuit for coarse gold, and a carbon-in-leach (CIL) circuit for fine gold. The plant operates at 92% mill availability and produces a target grind size of P80 75 µm. Studies are already underway to double throughput to 5 Mt/a, adding secondary crushing, a second ball mill, and a pre-leach thickener. The flowsheet also includes cyanide destruction via the SO₂/O₂ process to meet environmental targets for weak acid dissociable (WAD) cyanide below 2 mg/L before tailings deposition. The facility’s design head grade is 2.76 g/t Au, with gravity recovery contributing 45% of total gold and leach extraction adding 87%. This integrated approach ensures robust gold recovery while maintaining high environmental standards in the sensitive Newfoundland ecosystem.

Key Process Stages

• Stage 1: Primary Crushing – ROM ore is tipped into a hopper with a static grizzly and rock breaker. A vibrating grizzly (127 mm aperture) feeds a C130 jaw crusher operating at 75% availability, producing a P80 of 120 mm. A belt magnet removes tramp metal before the crushed ore is conveyed to a covered stockpile with 19 hours live storage.
• Stage 2: Grinding Circuit – Reclaimed ore feeds a 7.92 m Ø x 4.27 m EGL SAG mill (4,800 kW, VSD) with process water to maintain 70% slurry density. Discharge passes a trommel screen; undersize combines with ball mill discharge and gravity tails. Slurry is pumped to a hydrocyclone cluster (17 x 381 mm cyclones, 350% circulating load) to achieve a target P80 of 75 µm. Cyclone underflow feeds a 5.5 m Ø x 8.84 m EGL ball mill (4,800 kW fixed speed).
• Stage 3: Gravity Gold Recovery – A centrifugal concentrator with a feed scalping screen (+2 mm oversize returns to ball mill) recovers coarse gold. Concentrate is batch leached in a CS3000 intensive cyanidation unit using sodium cyanide and caustic. Pregnant solution is sent to electrowinning; tails return to the grinding circuit. Gravity recovery accounts for 45% of total gold.
• Stage 4: Pre-Aeration, Leach & CIL – Cyclone overflow passes a trash screen then enters one pre-aeration tank, two leach tanks, and eight CIL tanks in series (total 36 h residence at 42.5% solids). Oxygen/air sparging maintains dissolved oxygen, sodium cyanide dissolves gold, and lime controls pH at 10.5–11. Carbon is advanced counter-currently; loaded carbon is screened and sent to acid wash. The inter-tank screens retain carbon while slurry gravitates downstream.
• Stage 5: Cyanide Destruction & Tailings – CIL tailings enter a single mechanically agitated tank (1 h retention) where the SO₂/O₂ process (sodium metabisulphite as SO₂ source, copper sulphate catalyst, lime to pH 8.5) reduces WAD cyanide to <2 mg/L. Detoxified slurry is thickened to 65% w/w underflow and pumped to the TMF; overflow is reused as process water. Carbon safety screens capture any fine carbon for return to the CIL circuit.

Additional Interesting Data and Summary

The Valentine Gold Mine’s process plant is designed with robust metallurgical performance and environmental stewardship. Key technical details include a Bond Ball Mill Work Index of 16 kWh/t, Bond Rod Mill Work Index of 13.9 kWh/t, and an abrasion index of 0.41 g, indicating moderate abrasiveness. The ore specific gravity is 2.68 t/m³. The crushing circuit operates at 75% availability, while the mill achieves 92% availability. The pre-aeration plus leach residence time is 12 hours, and CIL residence time is 24 hours. Cyanide destruction maintains a WAD cyanide discharge target below 2 mg/L after 60 minutes of detox. Tailings are thickened to 65% w/w underflow for deposition. Environmentally, the closed-loop water system reuses thickener overflow and TMF decant, minimizing freshwater demand. The plant’s footprint in Newfoundland includes spill containment, sump pumps, and Safety Data Sheet stations for all reagents. Economically, the project achieved first gold pour in Q3 2025 and reached commercial production in November 2025. The planned expansion to 5 Mt/a will involve adding a second jaw crusher, secondary crushing circuit (HP450e cone crushers), a pebble crusher, a second ball mill, and a pre-leach thickener to increase slurry density to 50% w/w for improved leach kinetics. A sulphur burner will replace sodium metabisulphite as the SO₂ source. These modifications will maintain 93% overall recovery while treating lower head grade (1.68 g/t Au design for expansion). Sustainability initiatives include the use of electric rotary kiln for carbon regeneration, VSD on the SAG mill for energy efficiency, and advanced cyanide destruction to protect local water quality. The facility’s design accommodates future expansion with layout provisions for additional gravity concentrators and CIL tanks. The Valentine Gold Mine stands as a modern example of efficient gold recovery combining gravity, intensive leaching, and CIL technology in a remote Canadian environment.

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

Target Commodities: Gold, Copper