Gold Mountain Hits Up to 4,599 ppm Rare Earths at Irajuba Ahead of Leach Testing
Key Takeaways
- All five new diamond drill holes at the IR-1 Target returned significant intersections above the 400 ppm TREO cut-off, with the best result hitting 14.9m @ 3,520 ppm TREO and a sub-interval of 12m @ 4,051 ppm TREO.
- The length-weighted average MREO/TREO ratio of 43.50% across all holes confirms that nearly half of Irajuba's total rare earth content sits in the commercially critical magnet rare earth fraction — neodymium, praseodymium, dysprosium, and terbium.
- GMN has selected 23 composite samples from all five drill holes for preliminary ammonium sulphate leach screening at ALS in Brazil, with positive results to advance to confirmatory testing at ANSTO — the step that determines whether Irajuba qualifies as an Ionic Adsorption Clay deposit.
- Current drilling extends the mineralised system beyond the footprint of the December 2025 Exploration Target of 40–45Mt @ 1,200–1,400 ppm TREO, adding lateral and vertical confidence before any formal resource upgrade.
- GMN holds 100% ownership of the Irajuba Prospect, meaning all upside from metallurgical confirmation and any future resource upgrade accrues entirely to its shareholders.
Strong rare earth results confirmed at Irajuba as Gold Mountain advances to metallurgical testing
In an ASX announcement dated 30 September 2026, Gold Mountain Limited (ASX: GMN) reported highly anomalous rare earth assay results from five new vertical diamond drill holes at the Irajuba Prospect (IR-1 Target) in Brazil, with 192 samples confirming broad, consistent rare earth element (REE) mineralisation across the weathered profile. The results support progression to the next key milestone: metallurgical evaluation.
GMN holds a 100% interest in the Irajuba Prospect, its flagship REE project. Across 193.56 metres of total drilling, all five holes returned significant intersections above the 400 ppm TREO cut-off, with headline results including:
- IRDD260107: 14.9m @ 3,520 ppm TREO, 40.8% MREO/TREO (including 12m @ 4,051 ppm TREO)
- IRDD260110: 18.85m @ 2,568 ppm TREO, 44.7% MREO/TREO (including 2m @ 11,423 ppm TREO)
- IRDD260109: 4.2m @ 4,599 ppm TREO, 53.8% MREO/TREO
The length-weighted average MREO/TREO ratio across all holes was 43.50%, and Nd₂O₃ + Pr₆O₁₁ + Dy₂O₃ + Tb₄O₇ concentrations averaged 570 ppm, reaching up to 3,597 ppm.
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Drill results at a glance — key intercepts from the IR-1 Target
The table below summarises the best intersection per hole from the current drilling program at the IR-1 Target.
| Hole ID | From–To (m) | Intersection (m) | TREO (ppm) | MREO/TREO (%) |
|---|---|---|---|---|
| IRDD260107 | 9–23.9 | 14.9 | 3,520 | 40.8% |
| IRDD260108 | 7–21.35 | 14.35 | 2,709 | 45.9% |
| IRDD260109 | 24–35.2 | 11.2 | 2,239 | 51.4% |
| IRDD260110 | 11–29.85 | 18.85 | 2,568 | 44.7% |
| IRDD260111 | 9–25 | 16 | 2,153 | 43.2% |
Three observations stand out across the program:
The IR-1 Target has been building toward this point across successive campaigns, with earlier Irajuba drilling results already confirming broad mineralised intervals and elevated magnet rare earth ratios across the weathered profile before the current five-hole program was designed.
- Broad, near-flat-lying mineralised widths intersected across all five holes, consistent with a lateritic weathering profile on an old plateau surface
- Consistent grades above the 400 ppm TREO cut-off confirmed in every hole, with no low-grade anomalies or gaps undermining continuity
- Elevated MREO/TREO ratios averaging 43.50% across the program, indicating a substantial magnet rare earth component within the total REE assemblage
What rare earth elements and MREO/TREO ratios mean for investors
Understanding these results requires knowing what two acronyms actually measure.
TREO stands for Total Rare Earth Oxides — the combined weight of all rare earth oxide minerals present in a sample, expressed in parts per million (ppm). It is the headline grade figure. MREO stands for Magnet Rare Earth Oxides — the subset of those oxides with direct commercial applications in high-strength permanent magnets.
For the purposes of this announcement, GMN defines MREO as Gd₂O₃ + Y₂O₃ + Dy₂O₃ + Ho₂O₃ + Nd₂O₃ + Pr₆O₁₁ + Sm₂O₃ + Tb₄O₇. The MREO/TREO ratio tells you what proportion of the total rare earth content falls within this commercially critical subset. A higher ratio means more of the grade is commercially meaningful, not just volumetrically large.
The four key magnet rare earths — neodymium (Nd), praseodymium (Pr), dysprosium (Dy), and terbium (Tb) — are critical inputs for the permanent magnets used in electric vehicle motors, wind turbines, and defence systems. These are among the most strategically important materials in the global energy transition.
GMN is targeting Ionic Adsorption Clay (IAC) mineralisation. IAC deposits are a style of REE deposit where rare earth ions are adsorbed onto clay minerals within deeply weathered profiles, rather than locked into hard rock crystal structures. This distinction matters because IAC-style mineralisation is considered amenable to simple processing techniques such as heap leaching, which typically translates to lower processing costs and simpler metallurgy compared to hard-rock REE projects.
The 43.50% average MREO/TREO ratio confirms that a high proportion of Irajuba’s grade sits in the commercially valuable magnet rare earth fraction, not merely in total REE volume.
Director quote and metallurgical pathway
David Evans, Executive Director
“The latest diamond drilling results from the IR-1 Target at the Irajuba Prospect continue to demonstrate the extent and characteristics of the rare earth mineralisation within the weathered profile. The drilling has returned broad mineralised intervals with strong MREO/TREO ratios, including several higher-grade zones with significant Nd₂O₃ + Pr₆O₁₁ + Dy₂O₃ + Tb₄O₇ concentrations. These results further support the potential of the IR-1 Target and extend our understanding of the mineralised system beyond the area of the Exploration Target previously reported. The presence of mineralisation across both saprolite and saprock horizons, together with the strong magnet rare earth component, provides an important basis for the next stage of metallurgical evaluation. We are now preparing composite samples for preliminary ammonium sulphate leach testing at ALS, with selected samples to progress to confirmatory testing at ANSTO. This testing will assess the metallurgical characteristics and leachability of the mineralisation and determine whether it exhibits characteristics consistent with an Ionic Adsorption Clay (IAC) mineralisation style.”
Evans’ comments frame the immediate forward program clearly. With assay results in hand, GMN has moved to the metallurgical testing phase — the stage that bridges exploration results to resource evaluation.
A total of 23 composite samples have been selected from all five reported drill holes for preliminary ammonium sulphate leach screening. The key program details are:
- ALS method: ME-MS19 (ammonium sulphate leach screening)
- Location: ALS Geochemistry, Vespasiano, Minas Gerais, Brazil
- Sample coverage: 23 composite samples spanning all five drill holes across multiple depth intervals
- Follow-up pathway: Samples returning a positive leach response will advance to confirmatory ammonium sulphate leach testing at ANSTO
The ANSTO testing will assess the leachability and metallurgical response of the mineralisation and determine whether it exhibits characteristics consistent with an Ionic Adsorption Clay (IAC) mineralisation style. That determination is the critical question this program is designed to answer — and the outcome will shape GMN’s path toward a formal resource estimate.
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Investment case — what Irajuba’s results mean for GMN shareholders
These results do more than confirm grade. They confirm continuity across both saprolite and saprock horizons, adding both vertical and lateral confidence to a system that extends beyond the footprint of the previously declared Exploration Target.
That Exploration Target, declared on 17 December 2025, outlined 40–45Mt @ 1,200–1,400 ppm TREO for the IR-1 area. The current drilling extends GMN’s understanding of the mineralised system beyond that area — a meaningful expansion of the known footprint before any formal resource upgrade has been attempted.
The metallurgical pathway is now active. This is the de-risking step the market watches closely in REE projects: does the mineralisation actually leach? IAC-style deposits that respond positively to ammonium sulphate leaching are considered technically straightforward to process, which has direct implications for project economics. The ALS screening and potential ANSTO confirmatory testing will begin to answer that question.
Forward catalysts for GMN shareholders to monitor include:
- ALS ammonium sulphate leach screening results (program currently underway)
- ANSTO confirmatory leach testing, conditional on positive ALS screening outcomes
- Continued diamond drilling across the broader IR-1 Target
- Reconnaissance soil auger sampling and mapping to define additional resource drilling targets
GMN holds 100% ownership of the Irajuba Prospect. Beyond its flagship REE project, the company’s broader Brazilian portfolio includes lithium, copper, tungsten, and gold projects across multiple regions — though Irajuba remains the primary focus of the current work program.
For investors wanting to understand how GMN has funded the Irajuba drilling campaign and what capital is allocated to the broader Brazilian portfolio, our full explainer on Gold Mountain’s $5.5 million Brazilian exploration raise covers the placement terms, use of funds, and how the capital structure supports the current work program through to metallurgical evaluation.
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