Red Metal’s large-scale column leach tests confirm high rare earth recoveries from coarsely crushed Sybella ores using weak sulphuric acid, underpinning a low-cost heap leach development pathway.
- High rare earth extraction up to 78% on Saprock and Transitional ores
- Low acid consumption and impurities support economic processing
- Coarser crush sizes (-20mm) validated, promising cost savings
- 936 Mt inferred resource at 334 ppm NdPr and 31.7 ppm DyTb
- Pre-feasibility studies to be fast-tracked in 2026
Column Leach Tests Confirm Heap Leach Viability
Red Metal Limited (ASX:RDM) has delivered a compelling metallurgical breakthrough at its Sybella Rare Earth Project in Queensland. Large-scale column leach tests (CLT) on coarsely crushed ore from the Kary Zone have demonstrated strong rare earth element (REE) recoveries using weak sulphuric acid at ambient temperature. This validates the company’s long-held belief that the Sybella mineralisation is amenable to low-cost heap leach processing, a method that could significantly reduce capital and operating expenses compared to conventional processing.
The tests targeted two key mineralisation types, Saprock and Transitional, using representative composite samples crushed to -10mm and -20mm fractions. Both crush sizes achieved high extractions, with neodymium (Nd) and praseodymium (Pr); critical elements for permanent magnets; extracted at rates up to 78%. Heavy rare earths like dysprosium (Dy) and terbium (Tb) showed more modest recoveries around 40%, while yttrium and scandium extractions were lower but still measurable.
Operational Advantages from Coarser Crush and Low Acid Use
Notably, the similarity in leach performance between the -10mm and -20mm crush sizes suggests that the coarser -20mm fraction can be used without significant loss in recovery. This has important implications for reducing crushing energy, capital costs, and heap pad footprint, as larger particles enable higher stack heights and lower surface area. Acid consumption was low, averaging around 23-27 kg of H2SO4 per tonne of ore, and impurity levels in the pregnant leach solutions were minimal, which bodes well for downstream processing.
Between 35% and 55% of the total rare earth extraction occurred within the first 30 days of leaching, indicating potential for early cash flow once heap operations commence. The Fresh Granite mineralisation remains under test, with results pending, but the current data already supports a robust heap leach pathway for the bulk of Sybella’s mineralisation.
Large, Well-Defined Resource Supports Bulk Mining
The Kary Zone hosts a substantial inferred mineral resource estimate (MRE) of 936 million tonnes at 334 ppm NdPr and 31.7 ppm DyTb, including 182 Mt of Saprock and 157 Mt of Transitional mineralisation near surface. These friable, easily crushed granite-hosted ores offer a zero strip ratio, which is highly favourable for mining economics. The resource remains open to the southeast and at depth, suggesting further upside potential.
Red Metal compares the heap leach parameters at Sybella to those of large-scale soluble copper operations like Escondida in Chile and Morenci in the US, which use similar weak acid heap leach processing. While acknowledging that such analogies do not guarantee success, the comparison underscores the potential for a scalable, low-cost development.
Next Steps: Pre-Feasibility and Scale-Up Testing
With these definitive column leach results in hand, Red Metal plans to fast-track pre-feasibility studies targeting completion within 2026. The company is preparing further metallurgical optimisation tests, including larger diameter -30mm crush size columns and taller 6-metre columns to better simulate heap conditions. Ion exchange purification trials on pregnant leach solutions are also underway to refine the production of mixed rare earth carbonate products.
Managing Director Rob Rutherford emphasised the significance of the findings: “Our column leach tests have conclusively shown efficient extraction of light and heavy rare earths from coarsely crushed granite using weak sulphuric acid at ambient temperature. We aim to demonstrate that Sybella could be the Escondida of rare earths, unlocking a very large, low-cost rare earth development.”
While the results are promising, the company notes that final leach results for the Fresh Granite mineralisation are still pending, and commercial-scale mining and processing remain to be demonstrated. The upcoming pre-feasibility work will be critical to defining the project’s economic parameters and development timeline.
Bottom Line?
Red Metal’s validation of heap leach processing at Sybella marks a pivotal step towards a potentially low-cost, large-scale rare earth operation with early cash flow prospects.
Questions in the middle?
- How will the final leach results for Fresh Granite mineralisation impact overall recoveries and economics?
- What capital and operating cost estimates will emerge from the upcoming pre-feasibility studies?
- How will Sybella’s heap leach development fit into the global rare earth supply landscape amid rising demand?