Atlantic Gold's 2019 technical report for its Moose River operations in Nova Scotia describes the operating Touquoy plant and a satellite crusher at Beaver Dam. It also covers two 2.0 Mt/a gravity-flotation concentrators at Fifteen Mile Stream and Cochrane Hill, whose concentrates go to Touquoy for leaching.
The Moose River Consolidated Mine, Nova Scotia, Canada, NI 43-101 Technical Report was prepared by Ausenco and others, with an effective date of 25 March 2019. Its recovery methods draw on the 2015 and 2018 reports. The Touquoy plant was designed for 2 Mt a year, or 250 t/h at 8,000 operating hours (91.3%). It was running at about 2.24 Mt a year, 12% above design, and that rate is used in the 2019 life-of-mine plan. Plant staff had also cut cyanide consumption well below design while keeping recoveries high. The pre-leach thickener in the original design was found unnecessary during detailed design and removed. After five years of Touquoy ore, the plant switches to the harder, more abrasive Beaver Dam ore at the same rate, with only minor changes.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Report effective date | 25 March 2019 | Not applicable | Ausenco and others, for Atlantic Gold Corporation |
| Touquoy design throughput | 2 Mt/a (250 t/h) | Not applicable | Operating at about 2.24 Mt/a |
| Crushing | Modular three-stage jaw and cone, 381 t/h | Not applicable | 60% availability, P80 10 mm |
| Fine ore stockpile | 12,000 t total, 3,000 t live | Not applicable | Two slot belt feeders |
| Ball mill | 4.9 m x 8.1 m, 3,300 kW single pinion | Not applicable | P80 150 µm, 250% circulating load |
| Hardness | BWi 15.3 | kWh/t | 80th percentile of Beaver Dam ore |
| Gravity | Two parallel concentrator trains, 188 t/h | Not applicable | Up to 30% of cyclone underflow; ILR for 2.4 t/d of concentrate |
| CIL | Hybrid, 1 leach + 6 adsorption tanks of 1,169 m³ | Not applicable | 24 h at 50% solids |
| Reagents | NaCN 0.18, lime 0.59 | kg/t | Design |
| Elution | Pressure Zadra | Not applicable | Three electrowinning cells |
| Cyanide destruction | Air/SO2, 1.5 h, below 1 mg/L CNWAD | Not applicable | SMBS 0.5 to 0.6 kg/t |
| Satellite concentrators | Fifteen Mile Stream and Cochrane Hill, 2.0 Mt/a each | Not applicable | 92% availability, concentrate trucked to Touquoy |
Overview
The main Touquoy building houses grinding, gravity recovery, reagents, elution and the refinery, while crushing and CIL are outdoors. Run-of-mine ore is crushed in a semi-mobile three-stage plant and ground in a single-stage ball mill closed with hydrocyclones. A gravity circuit with intensive cyanidation treats part of the circulating load. The rest of the gold is leached in a hybrid carbon-in-leach (CIL) circuit. Loaded carbon is acid washed, stripped by pressure Zadra elution and electrowon, and barren carbon is regenerated in a kiln. Tailings go through air/SO2 cyanide destruction to the tailings management facility (TMF). For Beaver Dam, the primary jaw module moves to a satellite crushing station, and road trucks haul the crushed ore to Touquoy.
Key Process Stages
Touquoy crushing. Trucks tip over a sloped static grizzly, and a front-end loader supplements direct tipping from ROM stockpiles. A vibrating grizzly feeds the single-toggle jaw crusher. Secondary and tertiary cone crushers then produce P80 10 mm. A 95 m covered conveyor carries ore from the fine ore stockpile to the mill.
Grinding and gravity. The ball mill handles both ores without mechanical changes, running a lower ball charge for Touquoy ore. Mill discharge passes a rubber-lined trommel, and a density meter controls cyclone feed dilution. Two 50% gravity trains, each with a scalping screen and concentrator, return their tails to the mill. Concentrate goes to an intensive leach reactor, which has its own electrowinning cell in the gold room.
CIL. Trash screen undersize at minus 0.8 mm, mixed with flocculant, feeds the leach tank, or optionally CIL Tank 1 directly. Carbon at 10 to 15 g/L is advanced counter-current by air lift. Loaded carbon is pumped from Tank 1 to a recovery screen. A carbon safety screen on the tailings catches carbon from worn interstage screens.
Elution and gold room. Acid-washed carbon is eluted in a closed loop with two electrowinning cells. Barren carbon is regenerated in a kiln, quenched and sized back to Tank 6, with fines sent to the TMF.
Beaver Dam. A grizzly feeder, jaw crusher and 11,000 t stockpile (two days live) are installed at Beaver Dam before Year 6. A fleet of 22 road trucks of 31 t, each making nine trips a day, hauls the crushed ore. Tailings are rerouted to the mined-out Touquoy pit, and the reclaim barge moves there later.
Fifteen Mile Stream and Cochrane Hill. Each 2.0 Mt/a plant has jaw and cone crushing and ball milling, with gravity concentrators treating 50% of the circulating load, and rougher and cleaner flotation. A 2019 trade-off for Fifteen Mile Stream replaced a split circuit with coarse particle flotation at P80 240 µm. The chosen conventional flotation at P80 150 µm gave a USD 4.1 M NPV benefit and about 1.2% higher recovery. Cochrane Hill includes a HydroFloat coarse particle circuit with a regrind mill to about 100 µm. Concentrates are thickened, pressure filtered and trucked to Touquoy.
Touquoy upgrades for concentrates. Combined concentrates peak at about 18 t/h of solids. Gravity concentrate from the satellites would exceed 4,000 kg/d, five times the Touquoy and Beaver Dam rate, so a new intensive leach reactor and electrowinning cell are needed. Bottle roll tests showed most gold extraction from the flotation concentrates within eight hours, so the shorter leach time needs no circuit change. More frequent acid wash and elution cycles will be needed.
Additional Interesting Data and Summary
Analyses of the satellite concentrates found very low copper, lead, arsenic and mercury in the leach liquor and on carbon. Cyanide and lime use at Touquoy is projected to roughly double with the concentrates, within the existing reagent system capacity. Fresh water for the satellite plants is drawn from Archibald Lake.
In summary, the 2019 Moose River report treats the 2 Mt/a Touquoy gravity and hybrid CIL mill as a central leach plant. It takes Beaver Dam ore from a satellite crusher, and later gravity and flotation concentrates from the Fifteen Mile Stream and Cochrane Hill concentrators.
Key Processes
- Semi-mobile three-stage crushing
- Single-stage ball milling to P80 150 µm
- Gravity concentration and intensive cyanidation
- Hybrid carbon-in-leach
- Acid wash, pressure Zadra elution, electrowinning and kiln regeneration
- Air/SO2 cyanide destruction
- Satellite crushing and road haulage (Beaver Dam)
- Gravity and conventional flotation concentrators (Fifteen Mile Stream and Cochrane Hill)
Source: Moose River Consolidated Mine, Nova Scotia, Canada, NI 43-101 Technical Report, prepared by Ausenco and others, report effective date 25 March 2019.
Earlier report summaries
Earlier versions of this profile, based on older technical reports, are retained below for source traceability. Dates and figures reflect each report’s own effective date and are superseded by the current information above.
Moose River Consolidated — 2018 Technical Report
This technical report presents the Moose River Consolidated Project in Nova Scotia, Canada, covering the Phase 1 operation at Touquoy and Beaver Dam and the Phase 2 Expansion at Fifteen Mile Stream and Cochrane Hill, with an effective date of 24 January 2018.
Report context
This NI 43-101 Technical Report on the Moose River Consolidated Phase 1 and Phase 2 Expansion was prepared for Atlantic Gold Corporation, with an effective date of 24 January 2018. The Moose River Consolidated Project is located in Nova Scotia, Canada. The Phase 1 operation consists of the recently-commissioned Touquoy mine and the planned Beaver Dam mine. The Phase 2 Expansion includes the Fifteen Mile Stream and Cochrane Hill deposits. A Feasibility Study was completed in 2015 on Phase 1. A Pre-Feasibility Study was completed in 2018 on Phase 2, evaluating the two deposits as stand-alone mines with their own plants and infrastructure, feeding concentrates to the Touquoy leach facility. The economic analysis presents the combined Phase 1 and Phase 2 Expansion results.
Processing route
Touquoy Process Plant (Phase 1)
The Touquoy process plant is located east of Moose River, northeast of the Touquoy open pit and northwest of the tailings management facility. The process design assumes a conventional flowsheet, including crushing, grinding, gravity recovery, carbon-in-leach (CIL), desorption/electrowinning/refining, tailings management and cyanide destruction. The plant is designed for an ore treatment of 2,000,000 t/a or 250 t/h based on an availability of 8,000 h/a, or 91.3%. The crushing section design is set at 60% availability as it operates outdoors and uses modular mobile equipment. The plant will accept Touquoy ore for the first five years of operation and thereafter ore from the Beaver Dam deposit at the same treatment rate using the same unit operations. The main difference between the ores is that Beaver Dam ore is harder and has a higher abrasion index.
Fifteen Mile Stream and Cochrane Hill Process Plants (Phase 2 Expansion)
Two stand-alone 2 Mt/a capacity mills are proposed for Fifteen Mile Stream and Cochrane Hill. The process will generally be the same at both plants and includes primary, secondary and tertiary crushing, followed by grinding by a ball mill in a closed circuit with hydrocyclones. Centrifugal gravity separation units will be installed to recover primary cyclone underflow gravity recoverable gold. The fines will report to conventional flotation cells and the coarse will report to HydroFloat™ cells to produce gold concentrate. Gold concentrate will be thickened and pressure-filtered before being transported by truck to the Touquoy process plant. The final tailings from both fines conventional flotation and HydroFloat™ circuit will be pumped to a tailings management facility at each site. Plant operation will require reagent storage, air, water services and an assay laboratory at each site.
Modifications to Touquoy Process Plant
The Touquoy process plant leach circuit will require the trash screen and carbon safety screen single deck panels to be interchanged for a higher-flow product due to the increase in mass throughput when treating material from Cochrane Hill and Fifteen Mile Stream. Additional acid wash and elution cycles are expected to be required. Given the increase in mass throughput, the existing intensive leach reactor and downstream electrowinning cell has been identified as a bottleneck, and therefore a new intensive leach reactor and electrowinning cell will be required at Touquoy. Gold room operations will require more frequent sludge presses, drying batch and smelting activities.
Key reported parameters
| Parameter | Unit | Design Value | Basis |
|---|---|---|---|
| Phase 1 ore treatment rate | t/a | 2,000,000 | Proposed design |
| Phase 1 plant availability | % | 91.3 | Proposed design |
| Phase 1 crushing section availability | % | 60 | Proposed design |
| Phase 1 design throughput | t/h | 250 | Proposed design |
| Phase 2 Expansion mill capacity (each site) | Mt/a | 2.0 | Proposed design |
| Phase 1 gold recovery (Touquoy and Beaver Dam) | % | 94 | Testwork derived formula |
| Phase 1 recovery formula | , | % gold recovery = (((h-0.087)/h)*100) where h = head grade | Testwork derived |
| Phase 2 average LOM gold recovery (Fifteen Mile Stream) | % | 88.5 | Testwork based estimate |
| Phase 2 average LOM gold recovery (Cochrane Hill) | % | 88.3 | Testwork based estimate |
| Phase 2 first year gold recovery (Fifteen Mile Stream) | % | 92.9 | Testwork based estimate |
| Phase 2 first year gold recovery (Cochrane Hill) | % | 93.1 | Testwork based estimate |
| Phase 2 final year gold recovery (Fifteen Mile Stream) | % | 73.8 | Testwork based estimate |
| Phase 2 final year gold recovery (Cochrane Hill) | % | 70.8 | Testwork based estimate |
| Phase 1 Touquoy unit operating cost | C$/t milled | 20.9 | Feasibility Study estimate |
| Phase 1 Beaver Dam unit operating cost | C$/t milled | 34.6 | Feasibility Study estimate |
| Phase 2 Fifteen Mile Stream LOM unit operating cost | C$/t milled | 19.2 | Pre-Feasibility Study estimate |
| Phase 2 Cochrane Hill LOM unit operating cost | C$/t milled | 20.9 | Pre-Feasibility Study estimate |
Technical qualifications
The metallurgical testwork for Phase 2 Expansion was completed on variability and composite samples that had higher gold grades than the corresponding mine plan weighted average grade. The report states that testwork on higher grade samples tends to overestimate metallurgical performance. Further testwork is recommended on samples with feed grades approximating the mine plan feed grades to improve confidence in metallurgical recovery. The Phase 1 recovery formula for Touquoy and Beaver Dam was derived from testwork considering the very similar recoveries obtained for each deposit and the similar head grades.
No deleterious elements are expected in the doré from Phase 2 Expansion.
Source: Moose River Consolidated Project, Nova Scotia, Canada, NI 43-101 Technical Report on Moose River Consolidated Phase 1 and Phase 2 Expansion, effective date 24 January 2018. Relevant sections: 1.9, 1.14, 17, 13.
