Gold Mountain Extends Rare Earth Zone 13km West With Grades Up to 4,607 ppm
Key Takeaways
- 747 samples from 89 auger holes have confirmed rare earth mineralisation extends at least 13 km west of the Irajuba Exploration Target into the Ayrton Senna and Nova Itaipé Prospects.
- 27 holes returned intersections grading between 1,000 and 4,607 ppm TREO, with the best sub-interval hitting 4,607 ppm TREO at a commercially significant 58.5% MREO/TREO ratio.
- Most holes terminated within or adjacent to mineralised intervals, meaning the vertical extent of the system remains open — the program has tested the top of the profile, not the full depth.
- The median MREO/TREO ratio across intersections above 1,000 ppm TREO is 41.1%, above the 40% threshold generally considered commercially significant for ionic adsorption clay deposits.
- The next critical catalyst is ANSTO confirmation of IAC-style leaching behaviour, which would de-risk the project and open the pathway to a Mineral Resource estimate at Ayrton Senna.
Rare earth mineralisation extended 13 km west at Down Under Project
Gold Mountain Limited (ASX: GMN) has confirmed that rare earth mineralisation continues to expand across the Ayrton Senna and Nova Itaipé Prospects at its Down Under Project in Brazil. A total of 747 samples from 89 auger holes, averaging 8.4 metres in depth, have now confirmed the system extends at least 13 km west of the Irajuba Exploration Target into new ground.
The program has now confirmed that mineralisation commences close to surface across multiple drill sections, with 27 holes returning intersections grading between 1,000 and 4,607 ppm Total Rare Earth Oxide (TREO). Critically, most holes terminated within or adjacent to mineralised intervals, indicating the vertical extent of the system has not yet been fully tested.
David Evans, Executive Director
“The latest results from the Ayrton Senna Prospect at our Down Under Project continue to reinforce the scale and continuity of rare earth mineralisation being defined across the project, with mineralisation now being found up to 13 kilometres west of the Exploration Target previously drilled…”
These results are exploration geochemistry only. They do not form part of, and are not an extension of, the Irajuba IR-1 Exploration Target. No Mineral Resource or Exploration Target has been estimated for the Ayrton Senna Prospect.
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Drilling highlights: best intersections at Ayrton Senna
The standout results from the current program demonstrate both grade and strong Magnet Rare Earth Oxide (MREO) ratios:
- ASAD260113: 10m at 2,145 ppm TREO, 47.4% MREO/TREO from 9–19m (including a 2m sub-interval at 4,607 ppm TREO, 58.5% MREO/TREO from 12–14m)
- ASAD260057: 5m at 1,891 ppm TREO, 45.9% MREO/TREO from 10–15m
- ASAD260098: 5m at 1,748 ppm TREO, 48.9% MREO/TREO from 7–12m
- ASAD260099: 7m at 1,406 ppm TREO, 45.1% MREO/TREO from 7–14m
The fact that most holes terminated within mineralised intervals is a meaningful open-system indicator. It tells you the drill program has tested the top of the profile, not the full extent of it.
| Hole ID | Interval (m) | TREO (ppm) | MREO/TREO (%) | Depth From–To (m) |
|---|---|---|---|---|
| ASAD260113 | 10 | 2,145 | 47.4% | 9–19 |
| ASAD260113 (sub-interval) | 2 | 4,607 | 58.5% | 12–14 |
| ASAD260057 | 5 | 1,891 | 45.9% | 10–15 |
| ASAD260098 | 5 | 1,748 | 48.9% | 7–12 |
| ASAD260099 | 7 | 1,406 | 45.1% | 7–14 |
What is an ionic adsorption clay rare earth deposit?
Ionic Adsorption Clay (IAC) deposits are the global benchmark for economically extractable rare earths. They underpin Chinese dominance in REE production because the rare earth elements in these systems are loosely bound to clay minerals and can typically be extracted via simple, low-cost ammonium sulphate leaching, rather than the energy-intensive processing required for hard-rock deposits.
The most valuable fraction within these systems is Magnet Rare Earth Oxides (MREO), which include neodymium (Nd) and praseodymium (Pr), both critical for electric vehicle motors and wind turbines. MREO/TREO ratios above 40% are generally considered commercially significant. GMN’s best holes are reaching up to 58.5%, with a median ratio of 41.1% across intersections grading above 1,000 ppm TREO.
The Chemical Index of Alteration (CIA) is a measure of how deeply weathered the rock profile is. CIA values ranging from 99% to 74% recorded in the current holes indicate drilling has largely tested only the upper mineralised horizon, supporting the interpretation that additional rare earth enrichment may extend to greater depths within the saprolite zone. This is what makes the next phase of testing material.
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What comes next: metallurgical testing and the resource pathway
The metallurgical confirmation of IAC-style extraction behaviour is the next significant de-risking milestone for the project. The company’s stated next steps are:
- Selected mineralised intersection samples to be submitted to ALS for preliminary ammonium sulphate leach screening
- Favourable ALS results to be forwarded to the Australian Nuclear Science and Technology Organisation (ANSTO) for definitive IAC leach testing
- Areas passing ANSTO testing to be prioritised for diamond drilling, working toward resource estimation
- Additional auger assay results from Ayrton Senna remain pending from the ALS laboratory in Belo Horizonte
- Broader auger drilling to continue on a step-out basis, targeting stream sediment TREO anomalies
For context, the broader Down Under Project has an existing benchmark to measure against. The Irajuba IR-1 Exploration Target, confirmed in December 2025, was previously reported at 40–45 Mt at 1,200–1,400 ppm TREO. The Ayrton Senna results sit outside that target and represent a separate, expanding area of prospectivity.
The Irajuba discovery results established the original benchmark for the Down Under Project, with that program confirming the scale and grade profile that subsequent auger campaigns at Ayrton Senna are now being measured against.
If ANSTO testing confirms IAC-style leaching behaviour across Ayrton Senna intervals, it would meaningfully de-risk the project and support a future Mineral Resource estimate. That is the catalyst to watch.
For investors wanting to understand the funding mechanics behind the current drill campaign, our dedicated guide to the capital raise to advance Brazilian rare earth exploration covers the $5.5 million placement structure and how proceeds were allocated across the Down Under Project work program.
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