Heavy Rare Earths Uncovers Zones With 70% HREO Ratio at Subron Project
Heavy Rare Earths uncovers high-grade HREO zones at Subron project
Heavy Rare Earths has announced its strategic review has identified high-grade heavy rare earth oxide (HREO) mineralisation within the company’s Subron project in Western Australia. The project, formerly known as Cowalinya, has been renamed to reflect the submarine-like geometry of the mineralised lodes. The review identified 10 high-grade HREO domains across approximately 12.9km of mineralised strike, sitting within the existing JORC resource of 159Mt at 870ppm TREO.
The standout result came from the newly named Seawolf prospect, which returned 8m at 3,057ppm TREO with 1,344ppm HREO average and a 42% HREO ratio from 27m. The company also recorded a peak HREO ratio of 70%, which positions Subron as one of the highest HREO ratio residual clay deposits of its type. This could materially reposition Heavy Rare Earths’ value proposition in the critical minerals space.
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What are heavy rare earth elements and why do they matter?
Heavy rare earth elements (HREEs) are a subset of the 17 rare earth metals found in the periodic table. They are distinct from light rare earths and include elements such as yttrium (Y), terbium (Tb), and dysprosium (Dy), which are the highest-value components due to their scarcity and strategic importance. These elements are critical for the production of permanent magnets used in electric vehicles, wind turbines, and defence applications, including submarines under programmes such as AUKUS.
The HREO ratio refers to the proportion of heavy rare earth oxides relative to total rare earth oxides (TREO) in a deposit. A higher HREO ratio increases the economic value of a project because heavy rare earths command premium prices compared to their light rare earth counterparts. Projects with elevated HREO ratios can generate disproportionately higher revenue per tonne processed, making them strategically valuable in a market increasingly focused on securing critical minerals supply chains.
For investors, the presence of high HREO ratios in a deposit signals the potential for stronger project economics, as processing costs remain similar while revenue per tonne increases due to the higher value of heavy rare earths. This dynamic underpins the strategic interest in Subron’s newly identified high-grade zones.
Drilling data supports multiple high-grade corridors
The strategic review analysed 547 aircore drill holes drilled by Heavy Rare Earths and previous explorers, with a specific focus on HREO distribution constrained by regional magnetics and structural interpretation. Two key cut-off analyses were applied to the drilling database to identify high-grade zones:
| Cut-off Applied | Significant Intercepts | Individual 1m Intervals | Avg TREO (ppm) | Avg HREO (ppm) | HREO Ratio |
|---|---|---|---|---|---|
| >1,000ppm TREO | 190 | 583 | 1,685 | 441 | 25% |
| >300ppm HREO | 150 | 454 | 1,653 | 579 | 38% |
The 38% HREO ratio in the higher-grade dataset significantly exceeds typical clay-hosted rare earth deposits, which often exhibit HREO ratios in the low-to-mid teens. This elevated ratio underpins the potential for a higher-value resource at Subron, particularly when targeting concentrate production for processing.
The structural corridors constraining and controlling mineralisation have been named after historically submarine-prominent seas: Barents, Bering, and Bismarck. These corridors are interpreted to be elongated and strike-parallel with regional structures, suggesting a consistent geological control on mineralisation.
Priority prospects identified
Heavy Rare Earths has identified 10 named high-grade domains across the Subron project, with HREO ratios ranging from 30% to 66%. The priority target is the Seawolf prospect, which recorded the highest-grade intercepts on the project. Other named prospects include Nordenfelt, Oberon, Narval, Tunny, Virginia, Hunley, Blume, Flach, and Garrett.
The elongated, strike-parallel geometry of the mineralised zones is interpreted from underlying magnetics, which suggests that additional drilling along strike could extend the known high-grade domains. The company has noted that re-domaining the current JORC mineral resource will be required to better define these high-grade zones.
Additional drilling at Seawolf and other prospects will be required to better define the high-grade mineralisation and convert Inferred resources to Indicated. The identification of these priority prospects provides Heavy Rare Earths with a clear pathway to upgrade the resource confidence and quantify the high-grade, high-HREO material that could drive improved project economics.
Strategic location enhances development pathway
The Subron project is located 110km north-northeast of Esperance port in south-central Western Australia. The tenure sits on unallocated crown land in a non-farming area, which reduces potential land access complexities. The project is also well positioned logistically, situated 350km south of the Kalgoorlie Rare Earth Processing Facility, which was recently constructed.
Proximity to both deep-water port infrastructure and existing rare earth processing infrastructure could reduce capital requirements and development timeframes if the project advances. The Esperance port provides export capability, while the Kalgoorlie facility offers potential processing options for concentrate or feedstock material. These infrastructure advantages are material considerations for investors assessing the project’s development pathway.
Management commentary
Managing Director and CEO Jason Barnett emphasised the strategic value of the high HREO ratio zones identified in the review:
Jason Barnett, Managing Director and CEO
“The strategic review of Subron has been very rewarding, and the findings show it to be one of the highest HREO ratio residual clay deposits of its kind. This is supported by the drilling data showing 150 intersections grading above 300ppm HREO with an outstanding 441ppm HREO average grade and 38% HREO ratio. This has immense value and provides a clear point of difference from most rare earths projects. The opportunity for HRE is that these exceptional high-grade HREO ratio zones may be amenable to concentrate and yield a far higher value proposition for processing. It’s still early days and we have a lot of work to do on mineralogy, re-domaining the resource and metallurgical testwork, but with a significant amount of work done already, we have a head start and look forward to updating shareholders with the results.”
Consultant Claudio Sheriff, who led the strategic review, highlighted the significance of the HREO domain cluster:
Claudio Sheriff, Rare Earths & Critical Minerals Consultant
“Residual clay occurrences aren’t rare, however a cluster of HREO domains in a Sea of regional prospectivity, emerging at Subron, are remarkable.”
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Next steps for Subron
Heavy Rare Earths has outlined a comprehensive workstream to advance the Subron project:
- Completion of the strategic review with additional findings expected in the coming weeks
- Regional assessment to build additional scale and identify zones of secondary mineralisation for mineralogy characterisation work
- Re-domaining of the current JORC resource to better define high-grade zones
- Maiden high-grade, high-HREO-ratio mineral resource estimation
- Metallurgical testwork aimed at specific geological layers to simplify the processing flowsheet
- Potential resource infill drilling to convert Inferred resources to Indicated and extend high-grade domains
The company is investigating the availability of existing aircore drilling variability samples, which would avoid the need for re-drilling and enable fast-tracking of priority metallurgical testwork. This pathway targets upgrading the existing resource to higher-confidence categories while quantifying the high-grade, high-HREO material that could drive improved project economics.
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