Polymetals Unlocks High-Grade Silver Zone Once Written Off After 1996 Collapse
Polymetals confirms high-grade silver-lead-zinc mineralisation at Endeavor Mine
Underground diamond drilling has confirmed broad zones of high-grade silver-lead-zinc mineralisation in the upper Main Lode at the Polymetals Resources Endeavor Mine in Cobar, New South Wales. The area being drilled was historically considered sterilised following a 1996 ground collapse, but reinterpretation of historical mine data suggests the collapse zone may be materially smaller than previously assumed.
Eleven of the first 12 holes returned significant mineralisation, indicating substantial volumes of in-situ ore remain intact adjacent to the interpreted collapse boundaries. The mineralisation is adjacent to existing underground infrastructure and the high-grade Upper North Lode, enhancing potential for conversion to mining inventory. The drilling campaign comprises 34 holes totalling approximately 3,100 m, of which 713.6 m has been completed to date.
The location advantage is material. The mineralisation sits within an established mining environment, reducing the capital and development timeline typically required to access new ore zones. For investors, this represents a potential pathway to add high-grade tonnage to the existing mine plan without requiring new infrastructure.
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Standout drill results from the upper Main Lode
Silver equivalent grades from the first 12 holes range up to 494 g/t AgEq, with zinc and lead grades consistently above 5%. The thickness of intercepts, up to 45.2 m, provides evidence of substantial mineralisation widths that could support meaningful additions to the mine plan if continuity is confirmed across the remaining holes.
| Hole ID | Interval (m) | Silver (g/t) | Zinc (%) | Lead (%) | AgEq (g/t) |
|---|---|---|---|---|---|
| POL009 | 45.2 | 197 | 8.9 | 11.0 | 436 |
| POL002 | 33.0 | 209 | 9.9 | 8.1 | 439 |
| POL010 | 33.0 | 205 | 9.6 | 5.5 | 408 |
| POL007 | 24.5 | 207 | 12.2 | 6.8 | 473 |
| POL011 | 26.7 | 227 | 9.3 | 7.1 | 439 |
| POL008 | 14.9 | 304 | 8.5 | 5.9 | 494 |
The consistency of grades across multiple holes supports the view that the mineralisation is not isolated. These results are consistent with the existing high-grade Endeavor resource, indicating the upper Main Lode could contribute meaningfully to future mine life if the remaining drilling confirms continuity and the collapse zone boundaries are successfully delineated.
Why the 1996 collapse reinterpretation matters
A stope collapse in 1996 during previous mining operations led to the area being classified as largely sterilised and excluded from resource estimates. Polymetals’ review of historical mine records, survey data, and underground inspection now suggests the affected area may be materially smaller than previously interpreted. The current drilling program is designed to define the true boundaries of the collapse zone and assess how much mineralisation remains intact and accessible.
If confirmed, this reinterpretation could unlock significant additional high-grade ounces without the need for greenfield exploration, representing a low-cost pathway to resource growth. The company is systematically drilling around the interpreted collapse boundaries to establish where in-situ mineralisation begins, with 11 of the first 12 holes intersecting significant mineralisation providing early validation of the reinterpretation thesis.
Understanding silver equivalent calculations
Silver equivalent (AgEq) converts the value of multiple metals (zinc, lead, copper) into a single silver-equivalent figure, allowing investors to compare polymetallic intercepts on a like-for-like basis. This is particularly useful at Endeavor, where silver is the dominant metal but base metals contribute materially to revenue.
Polymetals uses the following assumptions: silver US$62/oz, zinc US$3,500/t, lead US$1,950/t, copper US$13,600/t, with metallurgical recoveries of 80% Ag, 89% Zn, 85% Pb, 85% Cu. Gold is not included in the AgEq calculation for this announcement. The calculation provides a standardised metric to assess the economic value of polymetallic deposits where multiple metals are recovered and sold.
Executive commentary on the drilling success
Jess Oram, Executive Director
“Our reassessment of historical mine records and new drilling suggest the extent of the 1996 stope collapse may have been considerably smaller than previously interpreted.
“The results from the first 12 holes provide strong support for that view. Every hole (bar one) has intersected significant mineralisation demonstrating that substantial volumes of high-grade silver-lead-zinc remain intact adjacent to the collapse boundaries.
“What makes these results particularly important is their location. The mineralisation occurs within an established mining environment, close to existing infrastructure and immediately adjacent to the high-grade Upper North Lode.”
Management’s confidence signals conviction in the geological reinterpretation and the potential for near-term resource additions. The proximity to existing infrastructure reduces the capital intensity and timeline typically required to bring new mineralisation into production, a material consideration for investors assessing the economics of resource growth.
Drilling program and next steps
The 34-hole, 3,100 m underground diamond drilling program is ongoing. The program is designed to improve geological confidence, assess continuity of mineralisation, and support evaluation of potential future mining opportunities within the upper Main Lode area. Results to date have provided sufficient encouragement to continue the full program.
- Total program: 34 holes, approximately 3,100 m
- Completed to date: 12 holes (713.6 m)
- Remaining: 22 holes
Continued positive results could support a future resource update and potential inclusion in the Endeavor mine plan. The remaining holes will focus on defining the eastern and western extents of the mineralisation and further delineating the collapse zone boundaries to establish the true volume of intact ore.
Endeavor Mine resource and reserve base
The upper Main Lode drilling represents potential incremental upside to an already substantial resource base at an operating mine. The current Endeavor resource and reserve base provides context for assessing the materiality of any future additions from the upper Main Lode area:
- Underground Mineral Resource (JORC 2012): 16.3 Mt @ 8.0% Zn, 4.5% Pb, 84 g/t Ag
- Sector 1 Tailings Mineral Resource: 5.2 Mt @ 2.12% Zn, 1.55% Pb, 79 g/t Ag
- Stage 1 Ore Reserve: 6.6 Mt @ 4.32% Zn, 2.04% Pb, 73 g/t Ag
The grades being reported from the upper Main Lode drilling are consistent with the existing underground resource, supporting the thesis that this area could be incorporated into the mine plan without dilution to average reserve grade. The proximity to the high-grade Upper North Lode and existing infrastructure further enhances the potential for economic extraction.
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Investment takeaways from the upper Main Lode results
- Infrastructure advantage: High-grade mineralisation confirmed adjacent to existing underground development, reducing potential capital costs and development timeline for conversion to mining inventory.
- Collapse zone reinterpretation: Review of historical data suggests the 1996 collapse zone may be materially smaller than previously assumed, potentially unlocking previously sterilised tonnage.
- Program continuation: Twenty-two holes remain in the drilling campaign to further define scale, continuity, and collapse zone boundaries, with positive results to date supporting program completion.
- Producer with growth optionality: Polymetals is positioned as an operating producer with near-term resource growth potential in a tier-1 Australian mining jurisdiction, supported by consistent high-grade drill results.
The upper Main Lode drilling program represents a low-cost pathway to potential resource growth at an operating mine. If the remaining holes confirm continuity and the collapse zone boundaries are successfully defined, the area could contribute meaningfully to future mine life without requiring new infrastructure development.
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