Overview
The Star-Orion South Diamond Project, historically known as the “Shore” mine due to its association with Shore Gold Inc. (now Star Diamond Corporation), represents one of the most significant undeveloped diamond resources globally. Located approximately 60 kilometers east of Prince Albert, Saskatchewan, within the Fort à la Corne forest, this project is poised to transition Saskatchewan from a potash and uranium powerhouse into a major player in the global diamond market. The project is situated on the traditional territory of the James Smith Cree Nation and encompasses the Star and Orion South kimberlites, which are part of the largest diamondiferous kimberlite cluster in the world.
The significance of the Shore mine project lies not only in its massive scale—boasting a projected mine life of 38 years—but also in its geological unique setting. Unlike the pipe-like kimberlites found in the Northwest Territories, the Fort à la Corne kimberlites are characterized by large, mushroom-shaped deposits formed by multi-phased volcanic events. This complex geology necessitated the development of a sophisticated mineral processing circuit designed to handle high volumes of material while maintaining high recovery rates for both macro and micro-diamonds. In 2018, a Preliminary Economic Assessment (PEA) conducted by SGS Canada Inc. estimated that the project could recover 66 million carats of diamonds over its lifespan, with a post-tax Net Present Value (NPV) of $2.0 billion. Currently, the project involves a joint venture/partnership framework involving Rio Tinto Exploration Canada (RTEC), which has brought Tier-1 mining expertise to the technical refinement of the processing flowsheet.
Key Process Stages
The mineral processing circuit at the Shore project is designed as a high-capacity, multi-stage system that prioritizes the preservation of large stones through the early use of X-ray Transmission (XRT) technology. The processing stages are as follows:
- Primary Crushing and Sizing: Run-of-Mine (ROM) kimberlite is delivered to a static feed bin and screened to 250 mm. Oversized material is processed through a jaw crusher to reduce the diameter, ensuring a consistent feed for the downstream scrubber.
- Scrubbing and Washing: The crushed kimberlite enters a high-capacity rotary scrubber. This stage is critical for removing the clay-rich matrix common in Saskatchewan kimberlites, which can otherwise interfere with gravity separation and diamond recovery.
- Secondary Crushing (HPGR): To liberate diamonds from the kimberlite host rock without causing breakage, the circuit utilizes High-Pressure Grinding Rolls (HPGR). This technology is preferred over traditional cone crushers as it uses inter-particle compression, which is gentler on larger gems.
- Dense Media Separation (DMS): The washed and sized material (typically +1.0 mm to -20 mm) is fed into a DMS circuit. Utilizing a ferrosilicon medium and 250 mm cyclones, the DMS separates high-density “sinks” (which contain diamonds and indicator minerals) from lower-density “floats” (waste rock).
- Primary Recovery (XRT): The modern flowsheet incorporates Tomra X-Ray Transmission (XRT) units. XRT technology identifies diamonds based on their specific atomic density, allowing for the recovery of large diamonds before they are subjected to further mechanical stress in the recirculating loads.
- Final Recovery (X-Ray and Grease): The DMS concentrate is treated through Flow-Sort X-Ray machines and traditional grease tables. Diamonds are naturally hydrophobic and adhere to the grease, providing a final capture stage for stones that might be missed by electronic sorters.
- Slimes Management: Fine waste (-0.5 mm) reports to a thickener where flocculants are added to recover process water. The resulting slimes are then safely disposed of in a dedicated Fine Management Area (FMA).
Critical Data
The following table summarizes the technical parameters and conceptual commercial scale data for the Star-Orion South Project based on the 2018 Preliminary Economic Assessment and subsequent technical updates.
| Parameter | Value | Unit |
|---|---|---|
| Target Throughput (Commercial) | 45,000 | Tonnes Per Day (tpd) |
| Project Mine Life | 38 | Years |
| Total Estimated Recovery | 66,000,000 | Carats |
| Primary DMS Cyclone Size | 250 | mm |
| Bottom Cut-off Screen Size | 1.0 – 1.1 | mm |
| Top Size Feed to DMS | 20 – 25 | mm |
| Crushing Circuit Capacity (Sampling) | 30 | Tonnes Per Hour (tph) |
| DMS Circuit Capacity (Sampling) | 10 | Tonnes Per Hour (tph) |
| Total Kimberlite Processed (LOM) | 470 | Million Tonnes |
| Post-Tax NPV (7% Discount) | 2,000 | Million USD ($2.0B) |
| Internal Rate of Return (IRR) | 19 | % |
Technical Details and Sustainability
The technical evolution of the Shore mine highlights a significant shift in diamond mineral processing: the move toward “bulk-sorting” and “early-stage recovery.” Because the Star and Orion South kimberlites have historically shown a presence of large, high-value Type IIa diamonds, the processing plant must minimize diamond breakage at all costs. Traditional crushing methods were found to be too aggressive; hence, the implementation of HPGR and XRT technologies. XRT units, in particular, allow the plant to “see” diamonds inside the ore stream before they are crushed, effectively future-proofing the mine against the loss of rare, large-carat stones.
One of the major technical challenges faced at the site is the management of the “overburden.” The kimberlites are buried under roughly 100 meters of glacial till and Cretaceous sands. This requires a massive open-pit stripping operation. The processing plant is designed to handle the high clay content (smectite and illite) found within the kimberlite, which can cause “viscosity spikes” in the DMS medium. To counter this, the scrubbing circuit is exceptionally robust, utilizing high-pressure water jets and significant retention times to ensure the material is thoroughly “de-gritted” before entering the cyclones.
From a sustainability and environmental perspective, the Shore mine is designed with a “closed-loop” philosophy. Water management is the primary focus. By utilizing high-efficiency thickeners, the project intends to recycle up to 90% of the process water, reducing the need for freshwater intake from local aquifers or the North Saskatchewan River. The 2018 PEA also explored the implementation of dry-stack tailings. Unlike traditional wet tailings ponds, dry stacking involves filtering the waste to a low moisture content (approximately 16%) and stacking it in a stable, manageable pile. This significantly reduces the risk of dam failure and allows for concurrent reclamation. As sections of the tailings stack reach capacity, they can be capped with saved topsoil and replanted with native forest species, ensuring that the Fort à la Corne forest is restored progressively throughout the 38-year life of the mine.
Furthermore, the project’s proximity to existing infrastructure—such as the 230 kV powerlines from the Nipawin and E.B. Campbell Hydroelectric stations—greatly reduces the carbon footprint compared to remote “fly-in” mines that rely on diesel power generation. The project’s integration into the provincial power grid allows for a more stable and environmentally friendly energy source for the high-torque HPGR and DMS pumps. Looking forward, the technical success of the Shore mine will likely serve as a blueprint for other large-tonnage, lower-grade diamond projects worldwide, proving that technological innovation in X-ray sorting and sustainable tailings management can make complex deposits economically viable.
Source: Shore | Star Diamond Corporation Technical Reports 2024
Source: NI 43-101 Technical Report
This article provides an overview of mineral processing developments based on publicly available technical reports and industry analysis.
