Overview
The North Island Project features a sophisticated mineral processing plant designed to handle varying ore characteristics across its three deposits (Northwest Expo, Red Dog, and Hushamu) through a staged expansion approach. The facility processes copper, gold, and molybdenum through integrated flotation and leaching circuits, with Phase 1 operating at 40 kt/d and Phase 2 expanding to 80 kt/d capacity.
Key Process Stages
- Phase 1 (Years 1-5): Single-stage crushing, SAG/ball mill grinding, bulk flotation, and separate rougher/cleaner tailings leaching circuits producing copper concentrate and gold doré
- Phase 2 (Years 6+): Duplicated crushing/grinding lines, pebble crushing, and new molybdenum flotation circuit to process Hushamu deposit material
- Crushing: Primary gyratory crusher reduces ROM from F80 475mm to P80 63mm (Phase 1) and 79mm (Phase 2)
- Grinding: SAG mills (35′ x 20′, 14MW) with ball mills (24′ x 33.5′, 11MW) achieve P80 of 150μm
- Flotation: Bulk rougher (300m³ cells) with regrind (7MW mill), followed by 3-stage cleaning to final concentrate
- Leaching: Dual CIL circuits (4800m³ tanks) for rougher/cleaner tailings with 24h residence time
- Molybdenum Separation (Phase 2): Dedicated circuit with NaHS depression, 5-stage cleaning including Jameson cell
Critical Data
| Parameter | Phase 1 | Phase 2 |
|---|---|---|
| Plant Capacity | 40,000 t/d | 80,000 t/d |
| Copper Head Grade | 0.24% | 0.22% |
| Gold Head Grade | 0.67 g/t | 0.30 g/t |
| Molybdenum Grade | – | 0.008% |
| Grinding P80 | 150 μm | 150 μm |
| Bond Ball Work Index | 10.4 kWh/t | 14.2 kWh/t |
| Bulk Flotation Mass Pull | 13.0% | 19.0% |
| Installed Power | 63.2 MW | 119.1 MW |
| Water Consumption | 3.2 Mm³/a | 11.8 Mm³/a |
Circuit Highlights
Phase 1 Configuration
- Single 450kW gyratory crusher feeding 14MW SAG mill
- Bulk flotation with PAX/MIBC collectors at 13% mass pull
- Dual leaching circuits for rougher/cleaner tailings
- Copper concentrate thickening (14m⌀) and filtration
Phase 2 Upgrades
- Duplicated crushing/grinding lines with pebble crushers
- Molybdenum circuit with NaHS depression (292 t/a consumption)
- Reconfigured leaching for cleaner tailings only
- Molybdenum concentrate drying system
Reagent System
The plant utilizes comprehensive reagent systems including:
- Lime (40,393 t/a Phase 1) for pH control
- Sodium cyanide (11,871 t/a Phase 1) for leaching
- PAX/3418A/MIBC for flotation
- SMBS (11,247 t/a Phase 1) for cyanide detox
- Specialty flocculants (326 t/a Phase 1) for thickening
Technical report and processing history
The following archived source profiles have been consolidated here to preserve the project’s processing history and study context.
Technical Analysis of the North Island Project: Advancing Copper-Gold Mineral Processing on Vancouver Island
Overview
The North Island Project, spearheaded by NorthIsle Copper and Gold Inc., stands as one of the most significant emerging porphyry copper-gold developments in Canada. Situated on the northern tip of Vancouver Island, British Columbia, the project occupies a strategic geographical position approximately 15 to 40 kilometers southwest of Port Hardy. This location is particularly advantageous for mineral development, offering year-round access to deep-water ports, a highly skilled local labor force, and established industrial infrastructure including paved highways and high-voltage power lines. The project encompasses several distinct deposits, most notably Hushamu, Red Dog, and the high-grade gold-rich Northwest Expo, which collectively represent a multi-decade resource potential for copper, gold, molybdenum, and the rare metal rhenium.
The significance of the North Island Project lies not only in its scale but also in its phased development approach designed to optimize capital expenditure while maximizing resource recovery. By targeting the higher-grade Red Dog and Northwest Expo deposits in the initial years, the project aims to establish a robust economic foundation before expanding to the massive Hushamu deposit. As global demand for “green metals” like copper continues to surge—driven by the international transition toward electrification and renewable energy—the North Island Project is positioned as a critical future supplier. Its proximity to the Pacific Rim markets via existing coastal infrastructure provides a distinct competitive advantage over more remote continental projects. Furthermore, the inclusion of rhenium, a critical element used in high-temperature superalloys for aerospace and defense, adds a layer of strategic importance to the project’s metallurgical output. This technical overview explores the complex processing circuit designed to handle the variable mineralogy of these porphyry systems, ensuring high-quality concentrates and sustainable operational practices.
Key Process Stages
The North Island processing facility is designed to evolve through two distinct phases, adapting to the mineralogical transitions as the mine moves from the initial high-grade satellite deposits to the larger, primary ore bodies. The circuit utilizes conventional flotation technology augmented by modern leaching techniques to maximize precious metal recovery.
- Primary Crushing: Run-of-mine (ROM) ore is reduced in size through a large-scale primary gyratory crusher. In Phase 2, a second crushing line will be commissioned to handle the increased throughput.
- Grinding Circuit (SAB/SABC): The initial phase uses a Semi-Autogenous Grinding (SAG) mill and a Ball mill (SAB). During Phase 2 expansion, a pebble crusher will be integrated into the SAG circuit (SABC) to maintain efficiency at higher tonnages. The ore is classified as moderately soft to medium-hard, with a Bond Ball Mill Work Index of approximately 17 kWh/t.
- Bulk Flotation: The ground slurry enters a bulk flotation circuit where copper and molybdenum sulfides are recovered along with associated gold. This stage focuses on high mass-pull to ensure maximum recovery of all value minerals.
- Regrind and Cleaning: To achieve marketable concentrate grades, the bulk concentrate is reground to a finer size to liberate chalcopyrite and molybdenite from pyrite and gangue minerals. Multiple stages of cleaner flotation are employed to reject pyrite.
- Molybdenum Separation (Phase 2): A dedicated molybdenum flotation circuit will be added in Phase 2. This circuit uses differential flotation to separate molybdenite from the copper concentrate, creating two distinct, high-value products.
- Concentrate Dewatering: The final copper and molybdenum concentrates are thickened and filtered to produce a dry cake suitable for transport to smelters.
- Tailings Leaching (Gold Recovery): A critical innovation in the flowsheet involves cyanide leaching of specific flotation streams (rougher and cleaner tailings). This stage targets gold that is not recovered in the copper concentrate, significantly boosting the overall gold doré production.
Critical Data
The following data reflects the metallurgical performance and design parameters for the North Island Project based on recent preliminary economic assessments and technical studies.
| Parameter | Value (Phase 1 / Phase 2) | Unit |
|---|---|---|
| Daily Throughput Capacity | 40,000 / 80,000 | tonnes per day (tpd) |
| Copper Recovery (Red Dog) | ~89.7 | % |
| Copper Recovery (Hushamu) | ~75.4 – 77.8 | % |
| Gold Recovery (Northwest Expo) | ~90.7 – 91.2 | % |
| Molybdenum Recovery (Hushamu) | ~44.6 – 49.2 | % |
| Bond Ball Mill Work Index | 17.0 | kWh/tonne |
| Primary Grind Size (P80) | 100 – 150 | microns (µm) |
| Projected Mine Life | 20+ | Years |
Technical Details and Sustainability
The metallurgy of the North Island Project is characterized by classic porphyry copper-gold-molybdenum mineralization, but with specific nuances required for each deposit. The Hushamu deposit, for instance, contains significant amounts of pyrite and occasionally higher clay content in certain alteration zones (such as the CMG and SCP zones), which requires careful reagent management to maintain copper selectivity. The Red Dog deposit, by contrast, demonstrates higher overall copper and gold recoveries due to its more favorable mineralogical assembly. One of the most technically compelling aspects of the North Island project is the recovery of rhenium. Rhenium is found within the lattice of molybdenite; as a result, the production of a high-grade molybdenum concentrate naturally serves as the vehicle for rhenium recovery, providing a high-value by-product that is rare in North American mining operations.
A primary technical challenge addressed in the flowsheet design is the optimization of gold recovery. Traditional copper flotation often leaves a significant portion of gold trapped in pyrite or other sulfides that are rejected to the tailings to maintain copper concentrate quality. NorthIsle’s solution involves a hybrid approach: while the bulk of the gold is recovered in the copper concentrate, the “scavenger” leaching of tailings streams allows for the capture of additional gold that would otherwise be lost. This significantly improves the project’s economics, particularly for the gold-rich Northwest Expo zone where gold grades are substantially higher than typical porphyry averages.
Sustainability and Environmental, Social, and Governance (ESG) factors are central to the project’s design. British Columbia has some of the world’s most stringent environmental regulations, and the North Island Project is being developed with a focus on minimizing its ecological footprint. The use of a phased expansion allows the company to manage capital and environmental disturbances more effectively. Water management is a critical focus, with the design emphasizing the recycling of process water to reduce fresh-water intake. Furthermore, the project’s proximity to existing infrastructure reduces the need for extensive new road construction or long-distance power line installations, which typically contribute significantly to the carbon footprint of new mines.
Social sustainability is equally prioritized through active engagement with local Indigenous communities, including the Kwakiutl, Quatsino, and Tlatlasikwala First Nations. The project is situated within their traditional territories, and NorthIsle has committed to a collaborative approach to ensure that the project provides long-term economic benefits, including employment and contracting opportunities, while respecting traditional land use and environmental stewardship. The future outlook for the North Island Project remains positive, with ongoing metallurgical testing and resource definition drilling expected to further refine the process flowsheet and potentially identify additional high-grade satellite zones that could further enhance the early-stage economics of this world-class copper-gold system.
Source: North Island
Source: NI 43-101 Technical Report
This article provides an overview of mineral processing developments based on publicly available technical reports and industry analysis.
