RESPEC's March 2024 technical report for Hecla Mining on the Casa Berardi mine in northwestern Québec, effective December 31, 2023, describes a SAG-ball mill, gravity and seven-tank CIL plant with paste backfill and a planned maximum of 4,400 t/d.
The NI 43-101 Technical Report on the Casa Berardi Mine, Northwestern Québec, Canada, was prepared by RESPEC for Hecla Mining Company with an effective date of December 31, 2023 and dated March 2024. Ore from the West Mine and the open pit is processed in the existing mill at 3,730 t/d, with a future maximum of 4,400 t/d. The report explains that gold is recovered by gravity concentration and carbon-in-leach (CIL). These were selected to recover the free gold efficiently and to reduce the preg-robbing effect of graphitic carbon in the ore on cyanide leaching.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Report effective date | December 31, 2023 | Not applicable | RESPEC for Hecla Mining Company; dated March 2024 |
| Throughput | 3,730 | t/d | Future maximum 4,400 t/d |
| Jaw crusher | 762 x 1,400 mm, 150 hp | Not applicable | 3,000 t ore storage bin |
| SAG mill | 5.5 m x 2.7 m EGL, 1,130 kW | Not applicable | Closed with a SAG screen |
| Ball mill | 4.0 m x 5.3 m, 1,325 kW | Not applicable | Ten operating 250 mm cyclones |
| Gravity | Two 762 mm Knelson concentrators | Not applicable | Gekko intensive leach reactor |
| Production thickener | 34 | m diameter | High-rate feedwell |
| CIL | Seven 700 m³ tanks | Not applicable | Cyanide and lead nitrate in tank 1 |
| Elution | Zadra, 5.5 t carbon | Not applicable | 870 kW water heater |
| Power | About 7 | MW | Not expected to change significantly |
| Water use | About 2.3 | Mm³/a | Make-up from the process water pond |
| Sodium cyanide, 2023 | 0.504 | kg/t | Lead nitrate 0.128 kg/t, iron sulphate 1.134 kg/t |
Overview
Since the previous report, the classification circuit has been changed from two-stage to single-stage cycloning to manage grinding circuit mass flows better. CIL, rather than carbon-in-pulp, puts gold in solution in immediate contact with activated carbon, which limits preg-robbing by graphite and maximizes recovery. After cyanide destruction, tailings go either to the paste backfill plant or to the tailings pond, and ferric sulphate is added to reduce arsenic in solution.
Key Process Stages
Crushing. Trucks tip ore over a static 5 m by 4.2 m grizzly, with a hydraulic hammer for oversize. A vibrating scalping screen with 89 mm openings sends oversize to a 762 by 1,400 mm jaw crusher. Crushed ore and screen undersize go to a 3,000 t ore storage bin.
Grinding. A weightometer and a moisture analyzer on the SAG feed conveyor control the dry feed rate, and dry quicklime is added at the SAG feed chute. The SAG mill runs in closed circuit with a vibrating screen. The ball mill runs in closed circuit with a single cyclone cluster, whose underflow is diverted to the gravity circuit as much as possible. Cyclone overflow passes a 700 µm trash screen to the production thickener.
Gravity. Cyclone underflow is split between two parallel circuits, each a vibrating screen ahead of a 762 mm Knelson concentrator. The gravity concentrate is leached in a Gekko intensive leach reactor (ILR) with hydrogen peroxide, cyanide and caustic soda. Its pregnant solution goes to a dedicated electrowinning cell.
CIL. Thickener underflow feeds seven 700 m³ CIL tanks in series, with cyanide and lead nitrate added to the first tank and compressed air to each. Carbon is added to tank 7 and pumped counter-current to tank 1. A safety screen recovers any fugitive carbon.
Cyanide destruction. Quicklime is added in a mixing tank. Two 322 m³ tanks then treat the slurry with sulphur dioxide, copper sulphate and compressed air before it goes to paste backfill or the tailings pond.
Carbon handling, elution and refining. The carbon, elution and electrowinning circuits run in batches. Loaded carbon is screened and stripped in a 5.5 t Zadra elution vessel, then acid washed for two hours with hydrochloric acid, rinsed and sized. It goes either to the calibrated carbon tank or to a 350 kW regeneration kiln. Pregnant solution is cooled through a heat exchanger and cooling battery, and two 4.53 m³ electrowinning cells recover the gold as sludge, which is filtered, dried and smelted to doré in a 125 kW induction furnace.
Additional Interesting Data and Summary
Reagent use in 2023 included 0.504 kg/t of sodium cyanide, 0.275 kg/t of caustic soda, 0.843 kg/t of sulphur dioxide, 0.176 kg/t of copper sulphate, 1.134 kg/t of iron sulphate, 0.128 kg/t of lead nitrate and about 1.5 kg/t of fine and coarse limestone combined. Power demand is about 7 MW and water use about 2.3 million m³ a year, with no supply concerns noted.
In summary, Casa Berardi's 3,730 t/d mill uses a straightforward SAG-ball, gravity and CIL flowsheet, chosen specifically so that carbon captures the dissolved gold before the graphitic ore can preg-rob it, and it sends part of its detoxified tailings underground as paste backfill.
Key Processes
- Grizzly, scalping screen and jaw crushing
- SAG milling with screen and ball milling with single-stage cyclones
- Gravity concentration with Knelson concentrators and Gekko intensive leaching
- Production thickening
- Seven-tank CIL with lead nitrate
- SO2/air cyanide destruction with ferric sulphate for arsenic control
- Zadra elution, acid wash, kiln regeneration, electrowinning and smelting
- Paste backfill and tailings pond deposition
Source: NI 43-101 Technical Report on the Casa Berardi Mine, Northwestern Québec, Canada, prepared by RESPEC for Hecla Mining Company, effective date December 31, 2023.
Technical report and processing history
The following archived source profiles have been consolidated here to preserve the project’s processing history and study context.
Casa Berardi Mine: Gold Extraction via CIL Processing
Overview
The Casa Berardi Mine operates a gold processing facility using a Carbon-in-Leach (CIL) circuit to address preg-robbing effects from graphitic carbon in the ore. The plant, operational since 2015, has undergone multiple upgrades to optimize throughput and recovery. The circuit integrates crushing, grinding, gravity concentration, and cyanide leaching with a design capacity of 1.4 million tonnes annually.
Key Process Stages
- Crushing: Ore passes through a static grizzly (500×500 mm), scalping screen (89 mm), and jaw crusher (762×1400 mm) before storage in a 3,000-tonne bin.
- Grinding: SAG mill (5.5m x 2.7m, 1,130 kW) operates in closed circuit with a vibrating screen (5×16 mm). Ball mill (4.0m x 5.3m, 1,325 kW) works with primary (660 mm) and secondary cyclones (250 mm) to achieve P80 of 91.5 µm.
- Gravity Circuit: Two Knelson concentrators (762 mm) recover 36.5% of gold, with concentrate processed in an intensive leach reactor (Gekko ILR).
- CIL Circuit: Seven 700 m³ tanks with 20-hour residence time, 24 g/L carbon concentration, and 450 ppm NaCN. Pulp density maintained at 50% solids.
- Carbon Management: Loaded carbon undergoes acid washing, elution (ZADRA process at 135°C), and regeneration in a kiln (0.76m x 7.3m, 350 kW).
- Gold Recovery: Electrowinning cells (4.53 m³) process pregnant solution, with gold sludge smelted in a 750-lb induction furnace.
Critical Data
| Parameter | Value | Unit |
|---|---|---|
| Throughput (2019) | 1.4 | Mt/a |
| Feed Grade | 2.8 | g/t Au |
| Overall Recovery | 86.7% | – |
| Grinding P80 | 91.5 | µm |
| CIL Cyanide Concentration | 450 | ppm |
| Reagent Consumption (NaCN) | 0.55 | kg/t |
| Tailings Cyanide (WAD) | <10 | ppm |
Major Equipment
- SAG Mill: 5.5m diameter x 2.7m EGL, 1,130 kW motor
- Ball Mill: 4.0m diameter x 5.3m length, 1,325 kW motor
- Production Thickener: 34m diameter high-rate type
- Elution Vessel: 1.68m diameter, 5.5t carbon capacity
Recent Upgrades (2017-2018)
- Increased SAG mill discharge grate area (3.1% → 4.0%)
- Ball mill pinion replacement for higher power draw
- New NKM screens in CIL tanks (2017)
- Enhanced cyanide destruction system (2019)
Casa Berardi — 2024 Technical Report (Recovery Methods)
Casa Berardi — 2024 Technical Report (Recovery Methods)
| Company | Hecla |
| Date | 2024 |
| Region | Quebec, Canada |
| Commodities | Gold |
Executive Summary
The Casa Berardi mill currently processes 3,730 tons per day (tpd) with a future maximum production capacity of 4,400 tpd. Gold extraction is performed using a combination of Gravity Concentration and Carbon In Leach (CIL) processes. These methods were specifically selected to optimize the recovery of free gold and reduce the preg-robbing effect caused by graphitic carbon present in the ore. The plant configuration is based on the current facility as of December 31, 2023, utilizing historical performance data and metallurgical test results to predict recovery.
The processing circuit begins with ore hauling from the West Mine headframe complex and open pit to a crusher dump pocket equipped with a static grizzly and pneumatic hammer. Crushed ore is stored in a bin before being conveyed to a SAG mill operating in closed circuit with a SAG screen. The ground ore is then processed through a ball mill and cyclone cluster. The cyclone underflow is diverted to either the gravity circuit or returned to the ball mill, while the overflow reports to a production thickener.
The gravity circuit utilizes Knelson concentrators and an Intensive Leach Reactor (ILR) to recover high-grade gold, which is then sent to electrowinning. The main CIL circuit consists of seven tanks in series, using activated carbon to adsorb gold from the pulp. The carbon circuit employs the Zadra process for elution, followed by electrowinning to produce gold sludge. Tailings are treated for cyanide destruction and arsenic reduction before disposal or paste backfill. The plant requires approximately 7MW of power and 2.3 million cubic meters of water annually.
Website: https://orezone.com/press-releases/orezone-gold-announces-transformational-expansion-into-canada-with-the-acquisition-of-the-casa-berardi-gold-mine/
Report Date: 2024
Region: Quebec, Canada
Project Status:
Commodity: Gold
Throughput:
Mine Life:
Mine Type:
Ore type:
Casa Berardi Mine: Gold Recovery via CIL Processing
Overview
The Casa Berardi Mine operates a gold processing facility using a Carbon-in-Leach (CIL) circuit to counteract preg-robbing effects from graphitic carbon in the ore. The plant, operational since 2019, integrates crushing, grinding, gravity concentration, and cyanide leaching to achieve an average gold recovery of 86.7%.
Key Process Stages
- Crushing: Ore passes through a grizzly screen, jaw crusher (762mm x 1400mm), and 3,000-tonne storage bin.
- Grinding: SAG mill (5.5m x 2.7m, 1,130 kW) and ball mill (4.0m x 5.3m, 1,325 kW) achieve a P80 of 91.5 µm.
- Gravity Circuit: Two Knelson concentrators (762mm) recover 36.5% of gold, with concentrate processed in an intensive leach reactor (Gekko ILR).
- CIL Circuit: Seven 700m³ tanks with 20-hour residence time, 24 g/L carbon concentration, and 450 ppm NaCN.
- Elution & Electrowinning: ZADRA process at 135°C/380 kPa produces gold sludge smelted into doré bars.
Critical Data
| Parameter | Value | Unit |
|---|---|---|
| Throughput | 1.4 | Mt/a |
| Feed Grade | 2.8 | g/t Au |
| Grinding P80 | 91.5 | µm |
| Cyanide Consumption | 0.55 | kg/t |
| Carbon Concentration | 24 | g/L |
Recent Upgrades
Key 2017-2018 optimizations included SAG mill liner redesign, ball size adjustments (125mm), and increased discharge grate area (4.0%). These raised throughput from 1.2 Mt/a (2015) to 1.4 Mt/a (2019).
