Giant Timor-Leste limestone prize firms for Estrella

Early drilling results from Estrella Resources’ Werumata limestone project in Timor-Leste have pointed to a bounty of clean, high-purity limestone, with intersections up to 55 metres thick, averaging a rich 84 per cent calcium carbonate. 

The company says the broad, consistent intersections support the push towards its goal of defining an inferred mineral resource of at least 500 million tonnes from the interpreted large-scale calcite deposit.

The available laboratory results were obtained from 11 holes, representing 25 per cent of the collected samples.

The drilling blitz focused on two extensive limestone plateaus near the coastal town of Uero-Mata and a potential port area, punching out 33 reverse circulation (RC) holes for 2804 metres and 9 diamond holes for 913 metres, for a total of 3717 metres. 

Timor-Leste authorities inspected the samples before dispatching them to PT Geoservices in Jakarta.

Results from the early holes show broad intersections of high-grade, low-impurity mineralisation. 

Key hits came from the upper Baucau Limestone, running up to 55m thick and averaging 84 per cent calcium carbonate. Holes in the underlying Batu Putih chalk intercepted up to 53m of calcium carbonate, averaging 80 per cent.

Samples for both rock units featured very low magnesium, averaging just 2 per cent magnesium oxide for the Baucau material and 1.3 per cent for the Batu Putih samples, confirming their suitability as low-magnesium limestones for acid-neutralisation and other industrial uses.

Estrella Resources managing director Chris Daws said: “Estrella continues to develop highly exciting prospects in Timor-Leste and we are very pleased to receive assay results from our maiden drilling campaign at the Werumata limestone project. These results confirm our geological modelling and the visual results reported at the time of drilling, meaning Estrella has strong potential to establish a large-scale limestone project.” 

Silica levels varied across the units, averaging about 7 per cent in the Baucau Limestone and 11 per cent in the Batu Putih Chalk. Other impurities were also low, with alumina generally below 2 per cent and up to 4 per cent, while iron oxide ranged from under 1 per cent to about 1 per cent.

The mineralisation at Werumata is interpreted as a young, shallow marine carbonate sequence. The uppermost Baucau Limestone Formation is less than 2 million years old and comprises former coral reef and related carbonate depositional environments typical of fore-reef, reef flats and shoreline deposits. 

These deposits are now exposed as partly eroded, dissected plateaus along the coast, thickening towards the north.

The younger Baucau Formation sits above the older Batu Putih unit, a roughly five-million-year-old sequence dominated by chalk and variable silica, with thin marl layers appearing in places. Both are underlain by the much older Noni Formation, which forms the deeper geological basement of the system.

Erosion along the boundary between the Baucau and Batu Putih formations has carved up the contact over time, explaining why the thickness of the underlying chalk can change from one spot to the next.

Importantly, the overall package is rich in carbonates and notably low in magnesium - a geochemical signature similar to modern reef systems. That chemistry opens the door to wide-ranging uses, from acid neutralisation in mining and environmental management through to construction materials and other industrial markets.

The company is now waiting on the remaining samples, which are still being processed at the Jakarta lab. Meanwhile, it continues to push towards a maiden resource estimate and the completion of early-stage development studies in a promising jurisdiction that offers Estrella a distinct first-mover advantage.

If Estrella can pull off its aspirational 500 million tonne high-grade limestone resource target, Weumata would be considered a genuine heavyweight by industrial minerals standards. 

A deposit of that scale, especially one dominated by clean, low-impurity calcite, would sit in rare company globally and have the muscle to support a major, long-life mining operation feeding multiple end markets for decades.

Combined with progress at its Ira Miri manganese deposit, the company’s interesting and rapidly evolving Timor-Leste commodity portfolio continues to deliver quality upside.

Is your ASX-listed company doing something interesting? Contact: matt.birney@businessnews.com.au