The 2024 Pre-Feasibility Study for the Black Pine Gold Mine describes a conventional run-of-mine heap leach processing route with associated solution management and gold recovery infrastructure.
Report context
This article is based on the 2024 Pre-Feasibility Study technical report for the Black Pine Gold Mine, dated 21 November 2024 (Revision 0, document reference M3-PN230328), which includes sections on recovery methods, heap leach infrastructure, and water management. The report presents a preliminary feasibility-level design for the project, including proposed processing and facility layouts.
Processing route
Run-of-mine heap leach
The selected gold recovery process is a conventional run-of-mine (ROM) heap leach. Ore will be mined by standard open pit methods from multiple pits. Ore will be truck-stacked directly on the heap without crushing, and lime will be added directly to haul trucks for pH control.
The stacking rate will follow the mine plan schedule, with ROM ore placement equivalent to a life-of-mine average of 50,000 tonnes per day.
Leaching and gold recovery
Gold in the stacked ore will be leached using a dilute cyanide solution applied via a drip irrigation system at application rates between 8,000 and 10,000 gallons per minute. Pregnant solution will be processed through a carbon adsorption circuit, with gold stripped from carbon via desorption. The resulting solution will undergo electrowinning to produce a precipitate sludge. This sludge will be treated in a retort oven for drying and mercury recovery, then refined in a melting furnace to produce gold doré bars.
Heap leach facility design
Facility siting and phasing
The heap leach facility (HLF) will be located at the eastern extent of the project area. The facility is designed in four phases to contain the estimated 299 million dry metric tonnes of leachable material: a Starter phase covering Years 1 and 2, Phase 2 covering Years 3 through 7, Phase 3 covering Years 8 through 12, and Phase 4 covering Year 13 through 18. Phasing is designed to accommodate the mine plan schedule and to improve recoveries by generally separating distinct metallurgical material types.
Liner and solution collection
The HLF solution containment system includes a composite liner comprising an HDPE geomembrane and a compacted soil liner, with an overlying solution collection system. Captured solution will be conveyed to process solution tanks.
Heap geometry and stacking
The heap is designed at 3H:1V side slopes to accommodate the closure footprint, with actual operational slopes including benching and steeper inter-bench face slopes. Maximum heap height will be 330 feet (100 metres), measured from pad grading to the top of the heap. ROM leachable material will be truck-stacked in nominal 30-foot (9-metre) lifts.
Contact water and event pond
Contact water will be routed to an Event Pond at the topographic low at the eastern extent of the HLF. The pond will be double-lined with an HDPE geomembrane liner and will include a leak detection and pumpback system. The Event Pond will also serve as overflow containment for the adjacent ADR plant, connected via a lined channel, and for the pregnant solution tank situated on a tank shelf within the pond.
Surface water management
Surface water diversions will route non-contact water away from the HLF, conveying clean runoff from native areas downstream to planned discharge points. Diversions are also planned around open pits, development rock storage areas, and stockpiles. Runoff from development rock storage areas will report to sediment control ponds prior to discharge, preventing sediment-laden water from leaving the site.
Design and operational safety
The HLF and associated structures are designed to meet regulatory requirements and industry-accepted standards appropriate for a PFS-level design. A Construction Quality Assurance program will be implemented to ensure construction materials meet specified requirements, with non-conforming materials either excluded or approved after confirming deviations do not affect performance. An Operations, Maintenance, and Safety manual will include instrumentation and monitoring for early warning, with the capital cost estimate including preliminary instrumentation systems. Final designs and significant design changes will be reviewed by a qualified third party.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Ore feed basis | Run-of-mine, no crushing | Proposed design |
| ROM placement rate | 50,000 tonnes/day (LOM average) | Proposed design |
| Solution application rate | 8,000–10,000 gallons/minute | Proposed design |
| Heap leach facility capacity | 299 million dry metric tonnes | Proposed design |
| Maximum heap height | 330 ft (100 m) | Proposed design |
| Lift height | 30 ft (9 m) nominal | Proposed design |
| Side slope angle | 3H:1V (closure), benched operational slopes | Proposed design |
| Leach facility phases | 4 (Starter, Phases 2–4) | Proposed design |
| Liner system | Composite: HDPE geomembrane + compacted soil | Proposed design |
| Pregnant solution treatment stages | Carbon adsorption, desorption, electrowinning, retort, melting furnace | Proposed design |
Project website: https://libertygold.ca/projects/black-pine/
Technical qualifications
The report states that the HLF and associated structures have been designed to meet regulatory requirements and industry-accepted standards suitable for a PFS-level design, and that additional investigations, evaluations, and analyses will be required at subsequent design phases to confirm assumptions and reduce the risk of unforeseen conditions during construction or operation.
Source: *Black Pine Form 43-101F1 Technical Report*, 21 November 2024, Revision 0, M3-PN230328, sections 1.14–1.16.
