Broken Hill Mines Drills High-Grade Centenary Zone Discovery at Rasp Mine

ASX: BHM Drills Thick High-Grade Centenary Intercept at Rasp Mine

Broken Hill Mines Limited (ASX: BHM) has reported a thick, high-grade silver-lead-zinc intercept from the first targeted drill hole below the Globe-Vauxhall Shear into the Centenary Zone at the Rasp Mine, with results that the company says are materially wider and higher grade than its current resource model predicted.

According to the ASX announcement released on 23 July 2026, drill hole WMDD6391 intersected 25.8 metres at 11.7% zinc equivalent (ZnEq), or 323 g/t silver equivalent (AgEq), from 415.1 metres, including 10.9 metres at 17.3% ZnEq, or 479 g/t AgEq, from 422 metres. The company stated that this intercept is approximately 500% wider and 27% higher grade in this location than the assumptions in the current 2024 Inferred Mineral Resource Estimate (MRE) for Centenary.

For investors, the significance is straightforward. The result may point to a larger and potentially more continuous ore zone near existing underground infrastructure, with an updated MRE for Centenary and the broader Rasp Mine targeted for Q4 CY2026.

The Headline Drill Result from WMDD6391

The company reported several mineralised intervals in hole WMDD6391, with the main interval standing out on both width and grade.

The current Centenary MRE is reported at 4.8 million tonnes at 9.2% ZnEq and 255 g/t AgEq, containing 39 g/t silver, 2.4% lead and 6.0% zinc. In that context, the new intercept suggests the local resource model may understate both thickness and grade in this part of the zone.

That does not in itself confirm a revised resource outcome. It does, however, explain why the company has moved quickly to accelerate drilling and reinterpret historical data.

"Initial results point to a major new discovery at the Rasp Mine, with an expected material expansion of the size and grade of mineralisation within the Centenary Zone compared to historical drilling and resource modelling."

— Broken Hill Mines Limited, ASX announcement, 23 July 2026

Why Drilling Below the Globe-Vauxhall Shear Matters

A central part of this update is not only the assay result, but also where it was drilled.

According to the company, the Globe-Vauxhall Shear has historically prevented accurate drilling into the Centenary Zone. A shear is a major zone of rock movement where drilling can become unstable and drill paths can bend away from the intended target. At Rasp, this meant previous holes passing through the structure were often distorted or abandoned.

As a result, only 24 holes have been drilled into Centenary since its discovery in 1983, and most of those were drilled from surface during the 1980s. The current resource interpretation was therefore built on relatively sparse data.

How Did the Company Overcome This Challenge?

Broken Hill Mines stated that it overcame this issue by:

1. Drilling a large-diameter pilot hole through the shear
2. Installing casing to stabilise that section
3. Drilling smaller daughter holes through the cased section into the Centenary target

This is important because better drill accuracy improves confidence in both geological interpretation and any future resource update. Furthermore, if follow-up holes continue to hit similar mineralisation, the company may be able to refine the Centenary model on a much stronger technical basis than was previously possible.

Centenary Zone: Scale, Location and Current Resource Context

In the company update, Centenary is described as one of the least-drilled parts of the Rasp system despite already hosting an inferred resource.

Broken Hill Mines reports that the Centenary Zone currently has:

• An Inferred MRE of 4.8Mt at 9.2% ZnEq
• Approximately 1,600 metres of strike length
• Approximately 280 metres of vertical plunge
• Mineralisation that remains open at depth and along strike in multiple directions

The location also matters considerably. The company said Centenary sits around 200 to 300 metres from current Rasp operations in the Western Mineralisation. In practical terms, that suggests any future development study may be able to assess the use of existing underground access, ventilation and haulage systems rather than requiring a standalone development footprint.

For investors, proximity to active infrastructure can influence future capital intensity. It does not guarantee development, but it can improve optionality if resource growth is confirmed.

Geological Differences Could Affect the Size Potential

The update also highlighted an early geological observation that may prove important as further work continues.

Broken Hill Mines said initial mineralogical work on WMDD6391 identified hedenbergite and tetrahedrite. These are minerals associated with the ore system and can help geologists compare one orebody with another. The company stated that this mineralogy appears more similar to the historic Main Lode than to the neighbouring Western Mineralisation.

Why Does the Geological Setting Matter?

According to the company, the Main Lode has historically been associated with a different style of mineralisation and has been mined intermittently for approximately 140 years. If Centenary is confirmed to be more closely related to that geological setting, it may support a revised interpretation of scale and continuity.

At this stage, that remains an initial assessment rather than a confirmed conclusion. The company said further analysis of historical drill pulps and new drilling will be completed to test this interpretation.

What Does ZnEq Mean and Why Do Investors Use It?

Polymetallic deposits such as Rasp contain more than one payable metal. In this case, the key metals are zinc, lead, silver, copper and gold. Because each metal has a different price and recovery profile, companies often report an equivalent grade to simplify comparisons.

Zinc equivalent (ZnEq) converts the value of all payable metals into a single figure expressed as if the value came from zinc alone. This helps investors compare one intercept with another, or compare a drill result against an existing resource estimate.

Broken Hill Mines reported the following formula in the ASX announcement:

ZnEq% = Zn% + (Ag g/t × 0.036) + (Pb% × 0.754) + (Cu% × 2.497) + (Au g/t × 3.033)

What Metal Price Assumptions Were Used?

The company used the following metal price and recovery assumptions:

• Zinc: US$2,650/t with 88.4% recovery
• Lead: US$2,000/t with 88.3% recovery
• Silver: US$35/oz with 75.0% recovery
• Copper: US$9,000/t with 65.0% recovery
• Gold: US$3,400/oz with 65.0% recovery

For a non-specialist investor, the practical takeaway is straightforward. When the company says the new intercept grades 11.7% ZnEq against a resource grade of 9.2% ZnEq, it is using a common framework that combines all the relevant metals into one comparable number. A related metric, AgEq, does the same thing but expresses the result as silver equivalent in grams per tonne.

Rasp Mine and Pinnacles Provide Operating Context

This drilling result sits within an operating mine setting rather than a standalone early-stage exploration project.

According to the company update, the Rasp Mine hosts three silver-lead-zinc sulphide orebodies:

Broken Hill Mines said Rasp operates a 750,000 tonnes per annum processing plant. In addition, the company stated that Centenary is being evaluated as a potential complementary ore source for possible plant expansion in the medium term.

The update also referenced the Pinnacles Mine, located around 15km south-west of Rasp. Under a binding joint venture agreement, BHM is the exclusive operator, with ore to be transported to the Rasp processing plant. Profits are shared approximately 70% to BHM and 30% to Pinnacles through a net smelter return-based arrangement.

This broader operational setting matters because exploration success near an existing plant can carry different economic implications than a new discovery requiring independent infrastructure.

What Is the Company Doing Next?

The company update set out a clear near-term work programme focused on confirming and expanding the Centenary result.

Broken Hill Mines stated that an accelerated drilling programme is already under way. It is also expediting a reinterpretation of historical Centenary drilling in light of the new intercept and revised geological understanding.

For investors, these next steps are likely to determine whether WMDD6391 proves to be a localised high-grade zone or part of a materially larger mineralised body.

Why This ASX Update Matters for Investors

This company update is significant because it combines three elements that investors tend to watch closely in the mining sector:

• A materially stronger drill result than the current model predicted
• A target located close to existing operations
• A defined catalyst pathway toward an updated resource estimate

The result does not yet establish a new resource, and the company will need additional drilling to confirm continuity and scale. Even so, the reported intercept has already challenged the assumptions used in the current inferred model for this part of Centenary.

If subsequent holes support similar widths and grades, the implications could extend beyond incremental resource growth. They may, moreover, affect mine planning, development sequencing and the role of Centenary within the wider Rasp production profile.

For now, the focus remains on follow-up assays and the planned Q4 CY2026 MRE update. According to the ASX announcement, those milestones are expected to clarify whether the first targeted hole below the Globe-Vauxhall Shear marks a broader change in the geological understanding of the Centenary Zone.

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