Heavy Rare EARTHS Ltd
Heavy Rare Earths Uncovers High-Grade HREO Zones at Renamed Subron Project
Heavy Rare Earths (ASX:HRE) has reported preliminary findings from a strategic review of its Subron Rare Earths Project in Western Australia, formerly known as Cowalinya, identifying a cluster of high-grade Heavy Rare Earth Oxide (HREO) domains within the existing resource base. This Heavy Rare Earths Subron high-grade HREO discovery at Seawolf Prospect marks a significant development, with the review conducted by rare earths consultant Claudio Sheriff outlining approximately 12.9 kilometres of high-grade HREO mineralised strike across 10 distinct high-grade domains, sitting within and beyond the current JORC resource of 159 million tonnes at 870 parts per million (ppm) Total Rare Earth Oxide (TREO).
According to the announcement, the standout intercept comes from the newly named Seawolf Prospect, returning 8 metres at 3,057ppm TREO, with an average of 1,344ppm HREO and a 42% HREO ratio. HRE has described this as one of the stronger intersections of its type reported from a residual clay deposit in Australia, though the company notes further verification work is required.
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What the Strategic Review Found
The review centres on a re-examination of 547 existing aircore drill holes, reinterpreted with a specific focus on HREO distribution rather than total rare earth content alone. Two grade cut-off thresholds were applied to the historical database, both producing notable results.
| Cut-Off Applied | Significant Intercepts | Avg. TREO Grade | Avg. HREO Grade | HREO Ratio |
|---|---|---|---|---|
| >1,000ppm TREO | 190 intervals | 1,685ppm | 441ppm | 25% |
| >300ppm HREO | 150 intervals | 1,653ppm | 579ppm | 38% |
The >300ppm HREO cut-off dataset spans 454 individual 1-metre intervals and delivers an average HREO grade of 579ppm. According to the company, this figure supports the view that Subron could represent one of the higher HREO-ratio residual clay deposits identified to date, though this assessment remains preliminary pending further technical work.
The HREO composition within this dataset includes yttrium oxide (Y₂O₃), dysprosium oxide (Dy₂O₃) and terbium oxide (Tb₄O₇), all of which are used as inputs in permanent magnets for electric motors, defence electronics and advanced manufacturing applications.
Ten High-Grade Domains Identified
The review has identified 10 interpreted high-grade HREO domains, each constrained by drill intercepts and supported by regional magnetic and structural interpretation. These domains are organised along regional structural corridors named the Barents, Bering and Bismarck corridors, which appear to influence the orientation of elongated, sub-parallel mineralised lodes.
Key domain findings from the report include:
- Approximately 12.9km of combined high-grade HREO mineralised strike identified across the 10 domains
- Additional high-grade targets identified outside the boundary of the existing JORC resource
- The Seawolf Prospect identified as the priority target, hosting the highest-grade intersections reported at the project to date
- Domains trending parallel to regional structural corridors, supporting the geological case for continuity along strike
"The preliminary findings of the focus on the distribution of the HREOs is awakening a re-rate at Subron as understanding of its composition evolves… Residual clay occurrences aren't rare, however a cluster of HREO domains in a Sea of regional prospectivity, emerging at Subron, are remarkable," said Claudio Sheriff, strategic review consultant to HRE.
Why the Rename Matters
The project's rename from Cowalinya to Subron, short for Submarine Squadron, reflects the interpreted elongated geometry of the HREO-rich lodes identified in the review. According to the announcement, the name also references the demand for heavy rare earths in next-generation submarine programs, including AUKUS.
The rename reinforces HRE's positioning of the project around heavy rare earths specifically, rather than the broader rare earths category. Elements such as dysprosium, terbium and yttrium place Subron in a different category from many light rare earth-dominated projects currently listed on the ASX.
The project is located on unallocated crown land, approximately 110km north-north-east of the port of Esperance and 350km south of the Kalgoorlie Rare Earth Processing Facility. Native title rights over the tenement have been granted to the Ngadju people, and cultural heritage agreements are in place to guide exploration activities.
Understanding HREO Ratio: Why It Matters to Investors
What Is HREO Ratio?
Rare earth elements are broadly divided into two groups: Light Rare Earth Oxides (LREO) and Heavy Rare Earth Oxides (HREO). The HREO group includes elements such as dysprosium, terbium, yttrium and erbium, among others. The HREO ratio expresses what percentage of the total rare earth content in a sample is made up of these heavier elements.
Why Does This Matter?
Heavy rare earths generally command higher prices than light rare earths and are considered harder to source globally. Dysprosium and terbium, in particular, are used in the production of permanent magnets that power electric vehicles, wind turbines and various defence applications. Most rare earths projects globally are dominated by light rare earths, meaning projects with elevated HREO ratios may occupy a differentiated position in the market.
Why It Matters at Subron
According to the strategic review, the >300ppm HREO cut-off dataset returned an average HREO ratio of 38%, with a peak of 70% identified in specific domains. The company notes this compares favourably to the average HREO ratio across most ionic clay deposits globally, which typically sits well below 20%.
Furthermore, whether this compositional profile translates into a higher-value product basket will depend on further processing and metallurgical work.
Glossary of Key Terms
| Term | Definition |
|---|---|
| TREO | Total Rare Earth Oxides, the sum of all rare earth elements expressed as oxides |
| HREO | Heavy Rare Earth Oxides, the subset of REOs with higher atomic weight, typically higher value (Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y) |
| LREO | Light Rare Earth Oxides, includes La, Ce, Pr, Nd, Sm |
| HREO Ratio | The percentage of total REO content made up of heavy rare earth oxides |
| Significant Intercept (SI) | A drill interval meeting a minimum grade threshold (in this case, >1,000ppm TREO or >300ppm HREO) |
| Residual Clay / Ionic Clay | A style of rare earth element (REE) deposit formed by weathering of granitic rocks, where REEs concentrate in clay layers |
| JORC Resource | A mineral resource estimate reported in accordance with the Australasian Joint Ore Reserves Committee code (2012) |
| ppm | Parts per million, the unit of measurement used for REE grades |
| Aircore (AC) Drilling | A lightweight drilling technique using a blade bit to recover clay and chip samples, suited to shallow near-surface mineralisation |
What Comes Next: The Work Program
According to the announcement, the strategic review remains ongoing, with HRE outlining a sequence of near-term and medium-term steps aimed at converting the geological findings into a formal high-grade resource and testable metallurgical outcome.
Near-Term Priorities
- Completion of the strategic review, with additional findings and formal recommendations expected in the coming weeks
- Assessment of existing AC drill variability samples to potentially support metallurgical testwork without additional drilling
- Mineralogy characterisation to identify the REE-bearing mineral species present in the highest-grade zones
- Re-domaining of the existing JORC resource to reflect the HREO-rich zones identified through the review
- A maiden high-grade, high-HREO-ratio mineral resource estimate for the newly defined domains
Medium-Term Work Program
- Metallurgical testwork focused on specific geological layers, aimed at simplifying the processing flowsheet
- Resource infill drilling intended to convert Inferred resources to the Indicated category and extend high-grade domain boundaries
- Additional drilling at Seawolf and other priority prospects to better define high-grade mineralisation
- Regional-scale assessment to identify further opportunities beyond the current resource footprint
"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… 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," said Jason Barnett, Managing Director and CEO of HRE.
The Investment Case: A Differentiated Asset
The announcement extends beyond a single exploration update, presenting a reframing of the Subron project around HREO ratio as a point of differentiation from many other rare earths projects on the ASX.
What Sets Subron Apart?
| Factor | Subron Position |
|---|---|
| HREO Ratio (>300ppm dataset) | 38% average |
| Peak HREO Ratio | Up to 70% in specific domains |
| Existing JORC Resource | 159Mt at 870ppm TREO |
| Mineralised Strike Identified | ~12.9km across 10 high-grade HREO domains |
| Seawolf Prospect | 8m at 3,057ppm TREO, 1,344ppm HREO, 42% HREO ratio |
| Significant Intercepts (>300ppm HREO) | 150 intercepts across 454 individual 1-metre intervals |
| Metallurgical Data | Up to 91% TREO recovery from Subron South using 5% hydrochloric acid at 30°C |
| Logistics | 110km from Esperance port, 350km from Kalgoorlie processing facility |
Preliminary leach testwork cited in the announcement indicates recovery of up to 91% TREO using a 5% hydrochloric acid solution at 30°C. HRE has characterised this as an early but encouraging indication that the mineralisation may respond to relatively straightforward processing conditions, though further testwork will be required to confirm this at scale.
Particle size analysis referenced in the JORC Table 1 disclosure also shows that 78.5% of REEs are confined to the -25 micron size fraction, with the grade of this fine fraction reported as 116% higher than the bulk saprolite feed grade. This concentration in the fine fraction may, consequently, have implications for beneficiation and the potential to produce a higher-grade concentrate, subject to further metallurgical confirmation.
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Why Investors Should Monitor Developments at HRE
The Subron strategic review remains at an early stage, though the preliminary findings outlined in the announcement point to a meaningful re-evaluation of the project's existing drill database. HRE has indicated that a portion of the resource may carry a different value profile than previously understood, based on HREO composition rather than TREO grade alone.
What Are the Key Upcoming Catalysts?
- Completion of the strategic review, with formal recommendations expected
- A maiden high-grade HREO resource estimate
- Metallurgical testwork results derived from existing drill samples
- Potential regional drilling to extend domain boundaries
Key Takeaway: The Heavy Rare Earths Subron high-grade HREO discovery at Seawolf Prospect has repositioned the Subron project around an HREO-enriched residual clay deposit with a 38% average HREO ratio, approximately 12.9km of high-grade mineralised strike, and preliminary metallurgical results indicating potentially straightforward processing characteristics. In addition, with a maiden high-grade resource estimate, mineralogy work and metallurgical testwork all flagged for the near term, the company's progress on these fronts will be a key focus for investors monitoring the heavy rare earths sector.
Want to Know More About Heavy Rare Earths and the Subron Project?
With a strategic review ongoing, a maiden high-grade HREO resource estimate on the horizon, and early metallurgical results pointing to a potentially differentiated asset, Heavy Rare Earths (ASX:HRE) is a company worth watching closely. Investors looking to stay across developments at the Subron Project — including upcoming catalysts such as formal review recommendations, mineralogy work, and metallurgical testwork — can access the latest information directly from the company by visiting the Heavy Rare Earths investor page.
