Broken Hill Mines (ASX: BHM) has hit a significant new bulk tonnage discovery at its Rasp Mine, revealing a 40m wide high-grade silver-lead-zinc zone that dwarfs previous resource estimates in the Centenary Zone.
- First targeted drilling below Globe-Vauxhall Shear yields thick, high-grade intercept
- Intercept 500% wider and 27% higher grade than 2024 Mineral Resource Estimate
- Mineralisation resembles historic Main Lode, suggesting step-change in scale
- Centenary Zone sits close to current operations, offering brownfields expansion potential
- Further drilling and resource update planned for Q4 2026
Breakthrough Drilling Unlocks New Bulk Tonnage Potential
Broken Hill Mines Limited (ASX:BHM) has announced a potentially game-changing discovery at its flagship Rasp Mine with the first-ever targeted drilling below the Globe-Vauxhall Shear into the Centenary Zone. The initial drill hole, WMDD6391, intersected a 40-metre wide zone of thick, high-grade silver-lead-zinc mineralisation, including a standout 25.8m interval grading 11.7% ZnEq and 323g/t AgEq starting at 415.1m depth. A higher-grade segment within this interval delivered 10.9m at 17.3% ZnEq and 479g/t AgEq, substantially exceeding expectations.
This intercept is roughly five times wider and 27% higher grade than the 2024 Inferred Mineral Resource Estimate (MRE) for the Centenary Zone, which was 4.8 million tonnes at 9.2% ZnEq and 255g/t AgEq. Such a significant upgrade in both thickness and grade indicates a material expansion opportunity for the Centenary mineralisation and a potential new bulk tonnage ore source near existing underground infrastructure at Western Mineralisation.
Geological Insights Point to a Step-Change in Deposit Scale
Mineralogical analysis reveals the Centenary Zone shares close affinity with Broken Hill’s historic Main Lode ore body, rather than the adjacent Western Mineralisation. This is an important distinction, as the Main Lode is known for its large-scale, high-grade deposits. The presence of minerals such as Hedenbergite and Tetrahedrite in the drill core supports this interpretation, suggesting the Centenary Zone may represent a previously underappreciated extension or analogue of the Main Lode system.
Historically, the Centenary Zone has been sparsely drilled, with only 24 holes mostly from surface and many dating back to the 1980s. Previous attempts to drill below the Globe-Vauxhall Shear were hampered by technical challenges, resulting in poor data quality and limited understanding of the zone’s true potential. BHM’s innovative drilling method, involving a large diameter cased hole through the shear and subsequent daughter holes, has overcome these obstacles and unlocked new exploration pathways.
Brownfields Expansion Near Existing Operations
Strategically, the Centenary Zone lies just 200–300 metres from current Rasp Mine workings, making it an attractive brownfields development target with potentially lower capital requirements than a greenfields project. The zone extends approximately 1,600 metres along strike and plunges vertically over 280 metres, with mineralisation remaining open at depth and along strike. This geometry offers multiple avenues for resource growth and mine planning.
Broken Hill Mines is accelerating reinterpretation of historic drilling and conducting follow-up drilling to confirm the extent of this new discovery. The company aims to define an exploration target and update the Mineral Resource Estimate for the Centenary Zone and the broader Rasp Mine by the fourth quarter of 2026. This update will be closely watched by investors given its implications for the mine’s feed profile and potential plant expansion.
Integration with Multi-Source Ore Strategy
The Centenary discovery complements BHM’s existing multi-source ore feed strategy, which recently benefited from the Pinnacles Mine restart delivering high-grade ore to the Rasp processing plant. This diversified feed approach has already driven record throughput and improved plant utilisation earlier this month, and the addition of a bulk tonnage, high-grade source from Centenary could further enhance operational flexibility and production growth.
With the Rasp Mine’s Consolidated Mining Lease renewed through 2047 and ongoing exploration success, Broken Hill Mines is positioning itself to capitalise on its core Broken Hill assets. The Centenary Zone discovery adds a new dimension to this growth story, offering a material resource expansion in a well-understood mining district.
Bottom Line?
The Centenary Zone drilling breakthrough opens a promising new chapter for Broken Hill Mines, but the true scale and economic viability hinge on upcoming resource updates and further drilling results.
Questions in the middle?
- How will the updated Mineral Resource Estimate reshape mine planning and capital allocation at Rasp?
- What are the metallurgical characteristics of the Centenary Zone mineralisation compared to existing ore sources?
- Could further drilling reveal extensions that materially increase the overall resource footprint?