Talon Metals' 2026 technical report for the Eagle nickel-copper mine in Michigan describes the converted iron ore mill at Humboldt. It averaged 83.2% nickel and 95.3% copper recovery from January 2025 to February 2026.
The NI 43-101 Technical Report on the Eagle Mine, Michigan, USA, was prepared for Talon Metals Corp, with a technical report effective date of April 29, 2026. Eagle ore is trucked on highway haul trucks to the Humboldt Mill, a former iron ore plant converted to treat it. The flowsheet has stayed virtually unchanged. Three-stage crushing, single-stage ball milling, bulk flotation and separation flotation produce separate nickel and copper concentrates at a nameplate 2,000 t/d (730,000 t a year). Nickel and copper recoveries for Eagle ore average 85% and 97%. Concentrates are railed to North American smelters. Tailings are deposited underwater in the former Humboldt iron ore pit, now the Humboldt Tailings Disposal Facility (HTDF).
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Report effective date | April 29, 2026 | Not applicable | Talon Metals Corp |
| Nameplate throughput | 2,000 t/d (730,000 t/a) | Not applicable | Humboldt Mill |
| Actual throughput | 56,783 t a month | Not applicable | Budget 61,091, January 2025 to February 2026 |
| Ore storage | About 10,000 t | Not applicable | Coarse Ore Storage Area (COSA) |
| Primary crushing | Jaw, minus 450 mm to P80 100 mm | Not applicable | Secondary and tertiary cones to P80 8 mm |
| Grinding | Two parallel single-stage ball mills | Not applicable | P80 130 µm; soda ash for pH control |
| Nickel concentrate | 13% Ni, 2% Cu | Not applicable | Design; 12.0% Ni actual |
| Copper concentrate | 31% Cu, 0.8% Ni | Not applicable | Design; 28.6% Cu actual |
| Recent recovery | Ni 83.2, Cu 95.3 | % | Actual; budget 84.4 and 95.7 |
| Concentrate moisture | 8 to 10 | % | Thickeners and filter presses |
| On-stream analysis | 12 streams | Not applicable | SGS-operated site laboratory |
| Mine plan | Through 2030 | Not applicable | Keel ore is harder |
Overview
Ore from the COSA is crushed in a jaw crusher and then secondary and tertiary cone crushers, stored in bins and reclaimed to two ball mill circuits closed with hydrocyclones. Rougher flotation makes a bulk copper-nickel concentrate, which is reground and cleaned to reject gangue. In a final separation stage, lime is added to split the copper and nickel minerals into two concentrates. Each concentrate has its own thickener and filter press and is loaded into railcars. Flotation tailings are thickened and pumped to the HTDF. Water from concentrate and tailings dewatering and from the HTDF is recycled to the plant.
Key Process Stages
Crushing. Front-end loaders load ore at the mine into road trucks. At the mill, the jaw crusher reduces nominal minus 450 mm ore to P80 100 mm. Secondary and tertiary cone crushers bring it to P80 8 mm.
Grinding. Two parallel single-stage ball mills, each closed with hydrocyclones, grind to P80 130 µm. Sodium carbonate is added for pH and water chemistry control.
Flotation. Rougher flotation recovers a bulk copper-nickel concentrate, which is reground and passed through cleaner stages. Lime is added in separation flotation to separate copper from nickel. The reagents are SIPX, MIBC, soda ash, lime, flocculant and CMC. An on-stream analyzer covers 12 streams and collects 12-hour shift composites.
Concentrate handling. The two concentrates are thickened and filter pressed to 8 to 10% moisture, stored in a covered building and shipped by rail directly to smelters.
Tailings. The HTDF is a pit lake in the former Humboldt iron ore mine, which closed in the late 1970s. It was used in the 1980s for Ropes Mine gold tailings and has taken Eagle tailings since 2014. Keeping sulphidic tailings under water limits oxidation and acid drainage. Water is managed through a water treatment plant and a zero liquid discharge plant and discharged under an NPDES permit.
Additional Interesting Data and Summary
The report attributes the 2024 drop in production to a mine incident that affected mill performance. The fall in 2030 reflects the last year of the mine plan. Keel ore is harder and may lower throughput compared with history. The copper concentrate averages about 30% Cu and is nearly 90% chalcopyrite. The nickel concentrate target is reviewed regularly against nickel price and smelting terms, and talc has not been a problem in the concentrate.
In summary, the 2026 Eagle report describes an established 2,000 t/d nickel-copper concentrator at Humboldt. It uses conventional crushing, ball milling, bulk flotation and lime-based copper-nickel separation, with underwater tailings disposal in a former iron ore pit.
Key Processes
- Jaw and cone crushing to P80 8 mm
- Two parallel single-stage ball mills to P80 130 µm
- Bulk copper-nickel rougher flotation
- Bulk concentrate regrind and cleaning
- Copper-nickel separation flotation with lime
- Concentrate thickening and filter pressing
- Sub-aqueous tailings disposal in a pit lake
Source: NI 43-101 Technical Report on the Eagle Mine, Michigan, USA, Talon Metals Corp, effective date April 29, 2026.
Consolidated report summaries
The following former standalone pages about this operation were consolidated here on October 25, 2026. They are retained for source traceability; dates and figures reflect each report’s own effective date and may be superseded by the current information above.
Eagle Mine: Humboldt Mill Nickel-Copper Processing Circuit
Overview
The Humboldt Mill is a repurposed iron ore processing facility that now processes nickel-copper ore from the Eagle Mine in Michigan, USA. This conventional milling operation features a three-stage crushing circuit, ball mill grinding, and flotation separation to produce high-grade nickel and copper concentrates. With a nameplate capacity of 2,000 tonnes per day (730,000 tpa), the facility achieves impressive metallurgical recoveries of 85% for nickel and 97% for copper.
Key Process Stages
- Ore Transport & Storage: Haul trucks deliver ROM ore to the 10,000-tonne Coarse Ore Storage Area (COSA)
- Crushing Circuit: Three-stage reduction (primary jaw crusher to 100mm, secondary/tertiary cone crushers to 8mm)
- Grinding: Two parallel single-stage ball mills operating in closed circuit with hydrocyclones (target P₈₀ of 100 microns)
- Flotation: Bulk flotation followed by separation flotation with regrinding and cleaning stages
- Concentrate Handling: Dewatering to 8-10% moisture via thickeners and filter presses before rail shipment
- Tailings Management: Subaqueous deposition in historic Humboldt iron ore pit (HTDF)
- Water Recycling: Comprehensive water recovery from dewatering operations and tailings
Critical Data
| Parameter | Value |
|---|---|
| Throughput (2021-2022 avg) | 59,380 t/month |
| Nickel Concentrate Grade | 13.04% Ni, 2% Cu |
| Copper Concentrate Grade | 30.5% Cu, 0.8% Ni |
| Nickel Recovery | 84.9% |
| Copper Recovery | 97.4% |
| MgO in Concentrate | 3.44% (avg) |
| Key Reagents | SIPX, MIBC, Soda Ash, Lime, CMC |
Process Innovations
The facility features an on-stream analyzer monitoring 12 process streams with 12-hour composite sampling by SGS. The operation demonstrates flexibility in concentrate grade targeting, adjusting nickel concentrate grades based on market conditions while maintaining strict MgO control below 6%.
Eagle Mine Humboldt Mill: Nickel and Copper Flotation Recovery
Eagle Mine Humboldt Mill: Nickel and Copper Flotation Recovery
Source: Unnamed_Company_81 (2026)
Website: https://talonmetals.com/talon-metals-completes-previously-announced-acquisition-of-lundin-minings-eagle-mine-and-humboldt-mill-operations-creating-a-multi-asset-u-s-nickel-copper-company/
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Throughput | 2,000 | tpd | Nameplate capacity; actual average monthly throughput Jan 2025–Feb 2026 was 56,783 t/month (~1,867 tpd) |
| Mill Power | N/A | kW | Not specified in source document |
| Target Grind Size | 130 | μm P80 | Product of ball mill grinding circuit |
| Head Grade | 1.46 Ni, 1.20 Cu | % | Feed grade for 2026 LOM plan; average Ni 1.46%, Cu 1.20% |
| Recovery % | 83.2 Ni, 95.3 Cu | % | Actual recovery Jan 2025–Feb 2026; long-term averages: Ni 85%, Cu 97% |
| Processing Capacity | 730,000 | tpa | Nameplate annual throughput based on 2,000 tpd |
| Energy Consumption | N/A | kWh/t | Not provided in source |
| Water Consumption | N/A | m³/t | Not specified; water from dewatering and HTDF is recycled for plant use |
| Operating Hours | N/A | hours/day | Not provided in source |
Overview
The Humboldt Mill, operated by Talon Metals Corp as part of the Eagle Mine project in Michigan, USA, is a former iron ore processing facility converted to recover nickel and copper from underground sulfide ores. Located near the Eagle Mine, the mill processes ore trucked from the mine via highway haul trucks to a Coarse Ore Storage Area (COSA) with 10,000 tonnes capacity. Since its conversion, the mill has employed a conventional three-stage crushing circuit followed by single-stage ball milling and a two-stage flotation process to produce separate high-grade nickel and copper concentrates. The facility boasts nameplate throughput of 2,000 tonnes per day (730,000 tonnes per year) and achieves metallurgical recoveries averaging 85% for nickel and 97% for copper, though recent monthly performance from January 2025 to February 2026 showed actual recoveries of 83.2% for nickel and 95.3% for copper. The significant copper recovery makes this operation a key North American supplier of critical battery metals. Tailings are deposited sub-aqueously in the former Humboldt iron ore open pit, now the Humboldt Tailings Disposal Facility (HTDF), minimizing environmental impact. The mill’s flowsheet remains virtually unchanged since commissioning, relying on proven technologies including bulk flotation, regrind, and separation flotation using lime to achieve final concentrate grades of 12–13% nickel and 28.6–30.5% copper.
Key Process Stages
- Stage 1: Three-stage Crushing – ROM ore (nominal minus 450 mm) undergoes primary jaw crushing to a P80 of 100 mm, followed by secondary and tertiary cone crushing to reduce the ore to a P80 of 8 mm. Tertiary crushed ore is stored in bins prior to grinding.
- Stage 2: Ball Mill Grinding – Crushed ore is fed to two parallel single-stage ball mill circuits operating in closed configuration with hydrocyclones, targeting a product P80 of 130 microns. Sodium carbonate is added for pH and water chemistry control.
- Stage 3: Bulk Rougher Flotation – The ground slurry undergoes bulk rougher flotation to produce a copper-nickel bulk concentrate, rejecting gangue minerals. Reagents include sodium isopropyl xanthate (SIPX), methyl isobutyl carbinol (MIBC), and carboxymethylcellulose (CMC).
- Stage 4: Regrinding and Cleaner Flotation – The bulk Cu-Ni concentrate is reground and subjected to multiple cleaning stages to further reject gangue minerals and upgrade the concentrate before separation.
- Stage 5: Separation Flotation and Dewatering – Lime is added to the bulk cleaner concentrate to selectively separate copper and nickel minerals. Final nickel concentrate (13% Ni, 2% Cu) and copper concentrate (31% Cu, 0.8% Ni) are dewatered to 8–10% moisture using thickeners and filter presses, then loaded into railcars for shipment to North American smelters.
Additional Interesting Data and Summary
The Humboldt Mill’s life-of-mine (LOM) processing plan for 2026–2030 outlines declining ore grades and throughput as the Eagle Mine approaches its end of life in 2030. Feed tonnage peaks at 787 kt in 2027–2029 before dropping to 497 kt in 2030, with nickel head grades decreasing from 1.46% to 0.95% and copper from 1.20% to 0.72%. Despite lower grades, overall recoveries are projected to remain robust, with nickel recovery ranging from 78.4% to 83.3% and copper recovery from 93.2% to 95.6%. Cobalt, gold, platinum, and palladium are also recovered as by-products, with cobalt recovery exceeding 79% and palladium recovery reaching 83.3%. The copper concentrate maintains a high quality of 30.5% Cu, while nickel concentrate targets 13% Ni, though recent actual nickel concentrate grade averaged 12.0% due to operational optimization for smelter conditions. The mill uses an on-stream analyzer for real-time monitoring of 12 streams and operates an onsite SGS laboratory for shift composites. Environmental management includes sub-aqueous tailings deposition in the former Humboldt iron ore pit (HTDF) and extensive water recycling from tailings and concentrate dewatering. Historically, a mine-related incident in 2024 temporarily depressed mill performance, but operations have since stabilized. Future challenges include the higher hardness of Keel ore, which may reduce throughput compared to historical averages. The facility’s strategic importance lies in supplying high-grade nickel and copper concentrates to North American smelters, supporting domestic battery metals supply chains. With a proven conventional flowsheet and strong metallurgical performance, the Eagle Mine and Humboldt Mill represent a model for sustainable sulfide ore processing in the Great Lakes region.
Key Processes: Flotation, Ball Mill, Crushing
Target Commodities: Copper, Nickel
