Estrella Resources Lifts Werumata Limestone Confidence With 274Mt Indicated Resource
Key Takeaways
- About 51% of the Werumata resource is now Indicated, with 274Mt at 84.7% ANC, up from a maiden estimate that was entirely Inferred.
- Roughly 70% of the 391Mt Product 1 resource is Indicated, giving the highest-quality limestone a firmer base for development studies.
- The total resource fell from 621Mt to 533Mt purely on lower bulk densities, with the modelled mineralised volume unchanged.
- The upgrade came from an expanded density program on existing core rather than new drilling, and no Measured Resource or Ore Reserve is reported.
- Excluding the low-value CL horizon would cut the central estimate to 430Mt, and no timelines, offtake agreements, costs or valuations are disclosed.
Werumata resource upgrade delivers 274Mt Indicated limestone resource
Most investors treat a resource number as a single headline. At Estrella Resources (ASX: ESR), the confidence behind the number matters more. The company has upgraded the Mineral Resource Estimate at its Werumata Limestone Project in Timor-Leste, with approximately 51% now classified as Indicated, compared with the entirely Inferred maiden estimate of 14 May 2026.
The headline figure is 274Mt Indicated at 84.7% ANC (Acid Neutralisation Capacity, a measure of how well the limestone neutralises acid). That represents approximately 70% of the 391Mt Product 1 resource. The total central estimate is 533Mt, made up of 274Mt Indicated and 259Mt Inferred.
The total is lower than the maiden estimate of 621Mt. The announcement attributes the reduction solely to changes in estimated bulk densities, and states the modelled mineralised volume is unchanged. In plain terms, the same rock volume is there, but each cubic metre weighs less than first assumed.
The updated resource is effective as at 15 October 2026. It was prepared by ASEAMCO Pty Ltd, with Robert de Jongh FAusIMM as Competent Person for Mineral Resource estimation.
Robert Mencel, Managing Director
“This is an important milestone for Werumata, with just over half of the Mineral Resource now classified as Indicated, including approximately 70% of our higher-quality Product 1 limestone…”
Mencel added that the upgrade gives “a stronger foundation as we progress discussions with potential customers…”
Resource by product and classification
The table below shows the central estimate (Table 1 of the announcement), in Mt.
| Category | Product 1 | Product 2 | Product 3 | Total |
|---|---|---|---|---|
| Indicated | **274** | – | – | **274** |
| Inferred | **117** | **33** | **109** | **259** |
| Total | **391** | **33** | **109** | **533** |
The lower to upper total range is 482Mt to 585Mt, with Indicated of 250Mt to 299Mt. These ranges reflect domain-specific bulk density variation and are not additional resources.
The products are defined by ANC:
- Product 1: ANC of ≥47% (average 83.9%), identified for acid neutralisation.
- Product 2: ANC of 20–47%, with potential uses in AAC blocks, masonry mortar and Portland cement blending.
- Product 3: ANC of <20%, with potential uses in aggregate, road base and fill.
No Measured Resource or Ore Reserve is reported, so this remains an early-stage resource.
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How did the density program deliver the upgrade?
The maiden estimate relied on laboratory bulk density measurements covering less than 3% of diamond drill core length. That limited the entire resource to Inferred, the lowest confidence category.
An expanded bulk density program was then undertaken on existing drill core, with measurements independently verified and audited by the Competent Person. Areas with sufficient geological, assay and bulk density information are now Indicated, while wider-spaced areas stay Inferred.
For you as an investor, the key point is that the main data limitation was addressed without new drilling.
What is a Mineral Resource classification?
Classification signals how much trust sits behind a tonnage figure. Inferred means lower geological confidence, based on limited data. Indicated means higher confidence, which supports development studies.
It does not imply economic viability. The announcement is clear that product specifications and commercial viability still require evaluation.
Density changes by horizon
| Horizon | Maiden t/bcm | Updated t/bcm | Updated category |
|---|---|---|---|
| BCUH | **1.88** | **1.69** | Indicated and Inferred |
| BPUH | **1.64** | **1.07** | Indicated and Inferred |
| BCUL | **1.58** | **1.58** | Inferred |
| LCL | **1.54** | **1.54** | Inferred |
| BPUX | **1.53** | **1.53** | Inferred |
| BPUL | **1.56** | **1.56** | Inferred |
| CL | **1.30** | **1.51** | Inferred |
t/bcm means tonnes per bank cubic metre. The shifts changed the tonnage mix: Product 1 fell from 493Mt to 391Mt, Product 3 rose from 95Mt to 109Mt, and Product 2 is unchanged.
What does the project look like?
Werumata sits in the Lautém Municipality, about 170km east-northeast of Dili, and is accessible by sealed all-weather roads. It is held by Estrella Resources Ltd Representação Permanente, a wholly-owned subsidiary, under an Exploration and Evaluation Concession awarded for four years from 14 May 2025.
The resource uses 33 RC holes (2,804m) and nine diamond holes (913m), all vertical and 41m to 140m deep. Mineralisation sits in the Baucau Limestone and Batu Putih Chalk. The technical report identifies open cut mining as the only economically feasible method, and all three products are direct shipping ores needing only crushing and screening.
Potential end uses include:
- Acid neutralisation agent for industrial and metallurgical applications
- Raw feed for cement manufacture
- Agent for agricultural soil amendment
- Construction aggregate
- Road base and fill material
The company points to Indonesia and Southeast Asia infrastructure development as an adjacent local market, with South, Southeast and North Asia offering additional export potential.
One caution from the ASEAMCO report: the relatively low economic value of Product 3 may lead to a decision not to mine the CL horizon. Excluding it would reduce the central estimate from 533Mt to 430Mt.
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What are the next steps for Werumata?
The company has disclosed four next steps:
- Progress technical and economic evaluation using the updated Mineral Resource.
- Advance discussions with prospective customers on product specifications, potential offtake arrangements and commercial applications.
- Continue engagement with the Timor-Leste Government on port access, infrastructure and potential export logistics.
- Undertake further community engagement and assess opportunities for additional drilling to test extensions and higher-quality limestone horizons.
The 2025 drilling tested only a small part of the concession, and the limestone extends more than 6km across the concession to its eastern boundary. No timelines, offtake agreements, costs or valuations are disclosed.
What the upgrade tells you is that confidence in the higher-quality Product 1 has improved, with the Indicated portion sitting inside the upgraded 533Mt. Estrella’s wider portfolio includes manganese at Ira Miri, where a 27,000t bulk sample was excavated, and copper-gold exploration.
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