Polymetals Grows Endeavor Mine Resource to 20.7Mt Despite Active Depletion
Key Takeaways
- Polymetals' Endeavor Mine global resource has grown to 20.7 Mt at 7.5% Zn, 4.2% Pb and 82 g/t Ag — the first full re-estimation since 2019 — despite 344 kt of active mining depletion between June 2025 and July 2026.
- The Upper Main Lode, newly defined through 29 drillholes, now contains 1.6 Mt at 8.5% Zn, 6.0% Pb and 234 g/t Ag — more than double the global resource silver grade — sitting adjacent to existing underground development infrastructure.
- Challenging the long-held assumption about the 1996 subsidence zone unlocked 1.3 Mt of additional mineralisation, converting a geological reinterpretation into a material resource addition.
- The resource grew in both tonnage and silver grade relative to the 2019 baseline (20.1 Mt at 70 g/t Ag vs 20.7 Mt at 82 g/t Ag) while applying a more conservative 5% density reduction — making the outcome more credible, not less.
- Outstanding assays from drilling after the 15 August 2026 data cut-off, plus eight holes testing a silver-rich supergene zone with localised gold up to 0.5 g/t Au, represent further resource growth catalysts not yet incorporated into the current estimate.
Endeavor’s global resource grows to 20.7 Mt despite depletion — here’s how
Polymetals Resources (ASX: POL) has delivered an updated Mineral Resource Estimate (MRE) for its Endeavor Mine in the Cobar Basin of New South Wales, growing the global in-situ resource to 20.7 Mt at 7.5% Zn, 4.2% Pb and 82 g/t Ag, despite ongoing mine depletion and the adoption of a 5% lower density assumption. The update, announced 7 September 2026, is the first full re-estimation of the entire Endeavor mine model since 2019.
The growth was driven by challenging a long-held geological assumption: the historic 1996 subsidence zone was found to be materially smaller than previously modelled, unlocking 1.3 Mt of mineralisation principally within the high-grade Upper Main Lode. Total contained metal now stands at approximately 1.55 Mt zinc, 0.86 Mt lead and 54.3 Moz silver.
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Q1 FY27 resource update: what the new numbers show
The updated MRE is classified and reported under JORC (2012) guidelines at a 5% Pb + Zn cut-off, depleted to 31 July 2026. The full classification breakdown is presented below.
| Classification | Tonnes (Mt) | Zn % / Pb % / Ag g/t | Contained Metal (Zn Mt / Pb Mt / Ag Moz) |
|---|---|---|---|
| Measured | 5.9 Mt | 7.6% Zn / 4.6% Pb / 82 g/t Ag | 0.45 Mt Zn / 0.27 Mt Pb / 15.4 Moz Ag |
| Indicated | 11.1 Mt | 7.5% Zn / 4.3% Pb / 86 g/t Ag | 0.83 Mt Zn / 0.48 Mt Pb / 30.7 Moz Ag |
| Inferred | 3.7 Mt | 7.4% Zn / 3.1% Pb / 70 g/t Ag | 0.27 Mt Zn / 0.11 Mt Pb / 8.2 Moz Ag |
| Total | 20.7 Mt | 7.5% Zn / 4.2% Pb / 82 g/t Ag | 1.55 Mt Zn / 0.86 Mt Pb / 54.3 Moz Ag |
Within the broader resource, the Upper Main Lode (UML) stands out as an exceptionally high-grade subset. It now contains 1.6 Mt at 8.5% Zn, 6.0% Pb and 234 g/t Ag, situated adjacent to existing underground development infrastructure. That silver grade — more than double the global resource average — reflects the silver-rich character of the upper mine levels that previous operators had undervalued due to a royalty agreement that provided little return on silver in concentrate.
How this compares to the 2019 baseline
Putting the 2026 result in historical context requires a consistent cut-off. At the comparable 5% Pb + Zn cut-off, the October 2019 estimate prepared by CBH Resources stood at 20.1 Mt at 7.4% Zn, with an overall silver grade of 70 g/t Ag.
The 2026 MRE at 20.7 Mt has grown in both tonnage and silver grade relative to that 2019 baseline, reaching 82 g/t Ag, despite years of active mining depletion by Polymetals and the adoption of a more conservative density assumption. That increase in silver grade reflects the newly defined silver-rich upper levels that were previously capped conservatively in resource modelling. The tonnage growth is all the more meaningful because it occurred after Polymetals mined 344 kt at 3.4% Zn, 2.3% Pb and 165 g/t Ag between June 2025 and July 2026.
What is a Mineral Resource Estimate — and why does this one matter?
A Mineral Resource Estimate (MRE) is a formal, independently verified calculation of the quantity and grade of mineralisation in a deposit that has reasonable prospects for eventual economic extraction. Under the JORC (2012) Code, resources are split into three confidence categories:
- Measured — highest confidence; suitable for detailed mine planning and production scheduling
- Indicated — good confidence; supports economic studies and prefeasibility work
- Inferred — lowest confidence; requires additional drilling to upgrade to a higher category
What makes the Endeavor result particularly significant for investors is that the resource grew despite active mining depletion, meaning Polymetals found more mineralisation than it extracted. The adoption of a more conservative density assumption — a 5% reduction informed by long-term mine reconciliation — makes the outcome more credible, not less. It demonstrates the company is applying rigorous, defensible methodology rather than flattering the numbers. A resource that grows in both tonnage and grade while applying tighter assumptions is a materially stronger result than headline figures alone convey.
Thinking differently: the strategy behind the Upper Main Lode discovery
The Upper Main Lode result did not happen by accident. Polymetals deliberately challenged the long-held assumption that the historic 1996 subsidence zone had sterilised substantial mineralisation in the upper levels of the mine. The company reinterpreted the geology, developed a new model, and executed a systematic underground drilling programme, with results reported across three successive announcements on 24 June, 22 July and 12 August 2026.
The successive drill results that built this case were released across three announcements, with high-grade drilling at the Upper Main Lode confirming the geological reinterpretation ahead of the full MRE incorporation.
Key points from the programme and updated model:
- The UML now contains 1.6 Mt at 8.5% Zn, 6.0% Pb and 234 g/t Ag
- It sits adjacent to existing underground development, meaning no new major infrastructure is required to access it
- 29 new drillholes were incorporated into the updated resource model
- The 5% density reduction was driven by historical mine reconciliation — a quality control discipline that strengthens the credibility of the estimate
- The Endeavor metallurgical plant has a nameplate capacity of 1.2 Mtpa and has demonstrated recoveries of 77% Pb, 87% Zn and 71% Ag
Executive Exploration Director Jess Oram
“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.”
Oram has confirmed that the approach has now demonstrably worked. The Upper Main Lode drilling converted a reinterpreted geological concept into 1.3 Mt of additional Mineral Resource, with the global Endeavor resource also growing in spite of both mining depletion and the application of more conservative density assumptions.
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What comes next for Polymetals at Endeavor
The company has outlined four specific next steps following this MRE update:
- Report outstanding assays from drilling completed after the MRE data cut-off of 15 August 2026 — these results were not included in the current estimate
- Assess the potential for subsequent resource updates as remaining Upper Main Lode and overlying supergene results become available for interpretation
- Complete detailed mine planning and geotechnical assessment of the newly defined Upper Main Lode resource
- Complete an Ore Reserve estimate for the Upper Main Lode
Beyond the UML programme, eight additional drillholes are currently testing the overlying supergene zone, which carries elevated silver grades and localised gold enrichment of up to 0.5 g/t Au in some areas. These supergene results were not included in the current MRE and represent a further potential resource growth catalyst that investors should monitor as assays are released.
Polymetals has also indicated that its growth strategy at Endeavor is progressively broadening beyond near-mine targets, with exploration extending across its wider licence areas in the Cobar Basin.
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