Polymetals Grows Endeavor Resource to 20.7 Mt with Upper Main Lode Boost

Resource Expansion Defies Mine Depletion

Polymetals Resources Ltd (ASX:POL) has unveiled a significant Mineral Resource update at its Endeavor Mine near Cobar, NSW, lifting the global in-situ resource to 20.7 million tonnes grading 7.5% zinc, 4.2% lead, and 82 grams per tonne silver. This comes despite ongoing mining depletion and the adoption of a more conservative 5% density reduction, underscoring the company's success in challenging long-held geological assumptions at this mature and heavily mined operation.

Central to the upgrade is the addition of 1.3 million tonnes of sulphide mineralisation in the Upper Main Lode (UML), previously interpreted as part of a 1996 subsidence zone. Polymetals’ reinterpretation, validated by targeted underground diamond drilling, has confirmed a substantial and high-grade remnant resource adjacent to existing underground infrastructure. The UML now hosts 1.6 Mt at a robust 8.5% zinc, 6.0% lead, and 234 g/t silver, offering a compelling foundation for near-term mine planning.

Comprehensive Resource Re-estimation Incorporates New Data

This Mineral Resource estimate (MRE) is the first full re-estimation of Endeavor since 2019, integrating data from 29 new drillholes, updated mine depletion to July 2026, revised surveys, and historical mine reconciliations. Polymetals has transitioned from a net smelter return (NSR) cut-off to a straightforward 5% combined Pb+Zn grade cut-off, aligning with historical reporting practices and reflecting current marginal operating costs.

The resource classification stands at 5.9 Mt measured, 11.1 Mt indicated, and 3.7 Mt inferred, with average grades holding steady despite the density adjustment. Silver grades have notably increased, driven by the recognition of silver-rich mineralisation in the upper levels previously underappreciated due to historical royalty constraints that limited silver extraction.

Strategic Growth Through Technical Innovation

Polymetals’ Executive Exploration Director Jess Oram emphasised the company’s commitment to growth through innovation: "Our ambition at Endeavor has never been simply to mine what previous owners left behind. We want to grow this mine, and we believe that growth will come from challenging old assumptions, developing new ideas and having the conviction to test them.”

Drilling has not only refined the footprint of the historic subsidence zone; now confirmed to be materially smaller than earlier interpreted; but also defined a significant remnant resource enriched in silver and with some local gold enrichment near the top of the system. The company continues to test the overlying supergene zone with further drilling underway, aiming to unlock additional resource upside.

Mining and Metallurgical Considerations

All mineralisation is underground, with Polymetals demonstrating that remnant mineralisation, including pillars and stope margins, can be mined using existing equipment and infrastructure. However, mining recovery in these complex areas may be lower due to geotechnical constraints. Notably, 63% of the Mineral Resource lies within five metres of existing stopes or subsidence areas, classified as stope skin, which introduces operational challenges.

The Endeavor processing plant maintains a nameplate capacity of 1.2 Mt per annum. Metallurgical recoveries average 77% for lead, 87% for zinc, and 71% for silver, with slightly lower recoveries in the weathered upper zones. High silver grades in the upper levels have supported direct shipping ore (DSO) production, with Polymetals having mined 31 kt of DSO grading 3.6% zinc, 3.9% lead, and 510 g/t silver up to July 2026.

Next Steps and Exploration Outlook

Polymetals plans to incorporate outstanding assay results from drilling completed after the MRE cut-off, which may further influence resource estimates. Detailed mine planning and geotechnical assessments for the UML resource are underway, alongside the preparation of an Ore Reserve estimate. Exploration is broadening beyond near-mine targets to include regional licences, reflecting the company’s systematic approach to resource growth.

The updated resource model benefits from extensive drilling data; over 3,000 holes historically, with 2,280 diamond drillholes used for estimation; and a robust geological framework refined over nearly five decades of study and mining. The reinterpretation and resource growth at Endeavor illustrate the value of applying fresh technical perspectives to legacy assets.

While the density adjustment and mining depletion temper headline tonnage gains, the net increase in resource despite these factors highlights the potential for further discoveries and resource extensions in this prolific polymetallic district.