West Cobar Metals (ASX:WC1) Re-analysis points to underreported antimony grades at Bulla Park

In a development that could reshape perceptions of its New South Wales asset, West Cobar Metals (ASX:WC1) has confirmed that prior assay methods likely underreported antimony grades at its Bulla Park deposit.

The company’s reassessment of core samples using a more complete peroxide fusion digest method has shown an average 14 per cent increase in antimony grades compared with earlier results derived from the conventional four acid digest approach.

Highlights

• Re-analysis of 19 mineralised samples revealed average antimony grade increases of 14 per cent, with individual samples up to 62 per cent higher.

• The discrepancy arises from volatilisation losses in the standard four acid digest method.

• All mineralised intersections at Bulla Park will now be re-analysed using the peroxide fusion method.

• The Bulla Park deposit currently hosts an Inferred Resource of 20 million tonnes at 0.30% copper, 0.10% antimony and 4.7 grams per tonne silver.

The Bulla Park copper, antimony and silver deposit, located 110 kilometres west of the Cobar mining hub, has been the centrepiece of West Cobar’s New South Wales operations.

Until now, the site’s resource estimates have relied on a four acid digest analytical method that, while effective for copper, can produce understated readings for antimony due to volatilisation during the digestion process.

By re-assaying selected intervals from holes drilled in 2023 and 2024, West Cobar has demonstrated a consistent pattern of underreporting. The revised peroxide fusion results suggest the deposit’s antimony endowment could be materially greater than previously modelled.

“Given intense global interest in antimony, we decided to run tests to validate the accuracy of previous assay results specifically for antimony at Bulla Park,”

said Managing Director Matt Szwedzicki.

“The underreporting seen across the two drill holes gives us encouragement that we may have more antimony in the system than previously thought.”

The existing Inferred Resource at Bulla Park stands at 20 million tonnes grading 0.30 per cent copper, 0.10 per cent antimony and 4.7 grams per tonne silver, equating to 60,000 tonnes of contained copper, 20,000 tonnes of antimony and three million ounces of silver.

In addition, an Exploration Target of 30 to 50 million tonnes at comparable grades has been defined, supported by gravity and geophysical data indicating mineralisation continuity beyond the current modelled area.

Metallurgical testing has already achieved strong recoveries — 94.6 per cent copper, 82.6 per cent antimony and 84.1 per cent silver — through flotation and leach processing. The company expects further optimisation of recoveries as test work advances.

The re-analysis initiative represents a crucial step in refining West Cobar’s understanding of Bulla Park’s true value.

The findings not only strengthen confidence in the project’s metallurgical profile but also point to potential resource upgrades once the complete dataset is available.

A staged 5,000 metre drilling program is planned to commence in early 2026 to expand the current Inferred Resource and test the broader Exploration Target.

For investors, the reassessment highlights how analytical precision can materially influence the perceived scale and economics of a deposit, particularly one containing a metal of increasing global strategic importance.

At a time when governments are racing to secure domestic sources of antimony, a redefined resource base at Bulla Park could position West Cobar more prominently in the critical minerals landscape.

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