Could Silica Variability Challenge Estrella’s Werumata Limestone Ambitions?

Initial Assay Results Confirm Geological Model

Estrella Resources (ASX, ESR) has announced encouraging initial assay results from its maiden drilling program at the Werumata Limestone Project in Timor-Leste. The assays, representing approximately 25% of samples collected from 11 drill holes (WLR001 to WLR011), validate the company's geological modelling and visual observations made during drilling in 2025.

The drilling campaign comprised 33 reverse circulation holes and 9 diamond drill holes, totaling 3,717 metres. The initial results highlight broad intersections of high-grade limestone and chalk, with the Baucau Limestone averaging 84.0% calcium carbonate (CaCO3) over intersections up to 55 metres, and the Batu Putih Chalk averaging 80.0% CaCO3 over intervals up to 53 metres.

Low Magnesium Content Enhances Project Appeal

Both limestone types exhibit very low magnesium oxide (MgO) concentrations, averaging 2% for Baucau Limestone and 1.3% for Batu Putih Chalk, classifying them as low magnesium limestones. This characteristic is particularly attractive for acid-neutralisation applications and other industrial uses where low impurities improve product quality and reduce processing costs.

Silica content varies between the two units, averaging around 7% in Baucau Limestone and 11% in Batu Putih Chalk, combining to an overall average of approximately 9%. While this variability may influence certain end-use specifications, the broad mineralisation and low impurity levels position the project favourably for multiple market segments.

Towards a Significant JORC Resource

Estrella is targeting a JORC-compliant Inferred Mineral Resource Estimate of at least 500 million tonnes, a substantial volume that could underpin a large-scale limestone operation. The initial assay results support this ambition, confirming the presence of thick, continuous mineralised zones close to true thickness.

Managing Director Chris Daws expressed optimism about the project’s potential, noting that the clean, low magnesium limestone could serve a variety of higher-value end uses, including environmental applications that benefit from reduced acidity and a lower environmental footprint. He also highlighted the momentum building across Estrella’s portfolio, including the nearby Ira Miri manganese pit.

Next Steps and Market Implications

Further assay results from the remaining samples are expected soon, with validation processes underway in Jakarta. These forthcoming data will be critical for refining the resource estimate and advancing feasibility assessments. Given the global demand for industrial minerals with low impurities, the Werumata Limestone Project could attract significant interest from both domestic and international markets.

Environmental approvals, project financing, and detailed market analysis will be key milestones as Estrella progresses. The company’s ability to deliver a robust, large-scale limestone resource in Timor-Leste could enhance its standing in the industrial minerals sector and contribute to regional economic development.