Heavy Rare Earths Uncovers High-Grade HREO Zones at Subron Project in Western Australia

Strategic Review Highlights High-Grade Heavy Rare Earth Oxide Concentrations at Subron

Heavy Rare Earths Limited announced preliminary results from a strategic review focusing on heavy rare earth oxide (HREO) distribution and grades at its Subron rare earths project. The company commissioned rare earths and critical minerals expert Claudio Sheriff to analyze the existing drilling database of 547 aircore holes completed by Heavy Rare Earths and previous explorers. This review uncovered hundreds of significant intersections, identifying higher-grade total rare earth oxide (TREO) and HREO domains, marking a substantial shift in the company’s understanding of the project’s resource composition and value.

According to Managing Director and CEO Jason Barnett, Subron hosts one of the highest HREO ratio residual clay deposits of its kind. The identification of multiple high-grade HREO domains distinguishes the project from many rare earth developments worldwide. These exceptional zones may be amenable to concentration, offering a significantly enhanced value proposition for downstream processing. The review remains in early stages, with further mineralogy, resource re-domaining, and metallurgical testwork planned.

Outstanding Drill Intercepts Over 12.9km of Mineralised Strike Across Ten Domains

The review identified approximately 12.9 kilometres of high-grade HREO mineralised strike and 10 high-grade domains within newly delineated structural corridors inside the company’s existing JORC-compliant 159 million tonne resource at 870ppm TREO. Additional high-grade domains were also found beyond the current resource boundary, indicating further exploration potential. These findings resulted from integrating regional magnetics and structural interpretation with the drilling data.

Notably, the Seawolf prospect returned an exceptional drill intercept (AC360) of 8 metres averaging 3057ppm TREO and 1344ppm HREO, representing a 42% HREO ratio from 27 metres depth. Applying a >1000ppm TREO cut-off revealed 190 significant intercepts comprising 583 individual 1-metre intervals averaging 1685ppm TREO and 441ppm HREO (25% HREO ratio). Using a >300ppm HREO cut-off identified 150 significant intercepts with 454 individual 1-metre intervals averaging 1653ppm TREO and 579ppm HREO (38% HREO ratio).

Rebranding to Subron Reflects Mineralisation Geometry and Strategic Rare Earth Uses

The project was renamed from Cowalinya to Subron to acknowledge the interpreted elongated submarine-like geometry of mineralised lodes and to emphasize the strategic demand for rare earth elements in next-generation submarine technologies. "Subron," short for submarine squadron, symbolizes the project’s potential amid rising geopolitical demand for rare earths in defense and advanced technology sectors. This rebranding aligns the company’s strategic positioning and investor messaging with the project’s evolving value proposition.

The geometric interpretation of structural corridors suggests mineralised zones exhibit elongated, submarine-like features, enhancing the structural framework and aiding identification of additional high-grade HREO domains. This naming strategy reflects a broader trend in the rare earth sector, where project names increasingly highlight strategic applications and geopolitical importance of critical minerals.

Prime Location and Logistics Near Key Processing Infrastructure

Subron is situated on non-farming, unallocated crown land in south-central Western Australia, approximately 110 kilometres north-northeast of the Esperance port and 350 kilometres south of the Kalgoorlie Rare Earth Processing Facility. This strategic location offers logistical advantages, including proximity to established port infrastructure and downstream processing capabilities, potentially facilitating efficient operations and offtake agreements for future production.

Located within Western Australia’s established mining jurisdiction, the project benefits from robust infrastructure, regulatory frameworks, and supply chain networks. Access to the Esperance port supports export logistics for rare earth concentrates or refined products, while closeness to Kalgoorlie’s processing facility may enable value-chain integration. These factors enhance the project’s economic feasibility as it advances through evaluation and exploration phases.

Heavy Rare Earth Oxide Distribution and Global Market Significance

The strategic review revealed Subron’s rare earth oxide distribution enriched in heavy rare earth elements such as europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and yttrium (Y). The discovery of higher-grade, high-value rare earth oxide compositions presents a compelling value proposition amid growing global demand for specific heavy rare earth oxides including yttrium oxide (Y2O3), terbium oxide (Tb4O7), and dysprosium oxide (Dy2O3).

Heavy rare earth elements command premium market valuations due to their critical roles in defense systems, renewable energy technologies, and high-performance permanent magnets. Subron’s exceptional HREO ratios, with peaks up to 70% in some areas, offer competitive advantages in product composition and downstream value realization. The company highlighted that these high-grade zones may concentrate effectively, delivering greater value compared to typical rare earth projects with lower HREO ratios.

Expert Consulting Drives Rare Earths Discovery and Evaluation

Heavy Rare Earths engaged Claudio Sheriff, a renowned rare earths and critical minerals consultant, to conduct the strategic review. Mr. Sheriff has extensive industry experience, contributing to notable discoveries such as Voltaic’s Strategic Resources (ASX:VSR) Neo MREO-Ga deposit, Asra Minerals’ (ASX:ASR) Yttria-REO-Scandium residual clay deposit, and Northern Minerals’ (ASX:NTU) Wolverine high rare earth element deposit. His expertise underpins the geological and resource assessment methodologies applied at Subron.

Mr. Sheriff noted that focusing on HREO distribution within the drill database, constrained by regional magnetics and structural interpretation, revealed a significant re-rating opportunity for Subron. While residual clay rare earth deposits are not uncommon, the clustering of high-grade HREO domains within a broader prospective region is remarkable, representing a distinctive geological feature among residual clay deposits.

Next Steps: Mineralogy, Resource Re-domaining, and Metallurgical Testing

Following the strategic review, Heavy Rare Earths plans further mineralogy studies to characterize mineral assemblages and crystal structures hosting rare earth elements. Resource re-domaining will update the resource model to incorporate newly identified high-grade HREO domains and structural corridors. Metallurgical testwork will assess the amenability of these zones to concentration and determine optimal processing methods for maximum value extraction.

Managing Director Jason Barnett emphasized that although the evaluation is in early stages, substantial preparatory work has been completed, providing a strong foundation to advance the project. The company expects to update shareholders on mineralogy, re-domaining, and metallurgical results as these programs progress. The discovery of 12.9 kilometres of mineralised strike and 10 high-grade domains across multiple structural corridors, plus additional domains outside the initial resource, offers a robust platform for next-phase development.

Robust Existing Resource and Enhanced Drill Data Analysis

The Subron project is supported by a JORC-compliant mineral resource estimate of 159 million tonnes at 870ppm TREO, announced in October 2023. The strategic review, disclosed on 30 June 2026, reassessed the existing drilling database without new drilling. The company analyzed 547 aircore drill holes from prior exploration, applying refined analytical frameworks emphasizing HREO distribution and grade optimization. This approach leverages existing data to identify higher-grade domains suitable for selective mining or processing strategies.

The review filtered drill data using >1000ppm TREO and >300ppm HREO cut-offs, identifying 190 and 150 significant intercept intervals respectively, each comprising multiple 1-metre samples. The focus on HREO distribution, constrained by regional magnetics and structural interpretation, provided a systematic method to delineate prospective domains. Identified structural corridors and domains extend within and beyond the current resource boundaries.

Strategic Advantages and Market Differentiation in the Global Rare Earths Industry

These preliminary findings position Subron as a competitively differentiated project in the global rare earths sector due to its high HREO ratios and concentrations. Globally, rare earth deposits are typically dominated by light rare earth elements, with heavy rare earths as a minor fraction. Subron’s multiple high-grade HREO domains, with peak ratios up to 70%, indicate a unique composition within residual clay deposits. This advantage may translate into higher prices for rare earth concentrates or refined products, reflecting current market premiums for heavy rare earth elements.

The strategic review signals a shift from a conventional rare earth resource development approach to a value-focused heavy rare earth element strategy. This aligns with market trends and geopolitical drivers fueling demand for specific heavy rare earths in defense, renewable energy, and advanced technology sectors. The company is evaluating development pathways prioritizing high-grade HREO production over conventional concentrates, which may influence future exploration, development, and operational priorities as the project progresses.