Stellar Resources Delivers Major Resource Upgrade at Heemskirk Tin Project

Stellar Resources Delivers Major Severn Resource Upgrade as Heemskirk Tin Inventory Passes 129,000 Tonnes

Stellar Resources (ASX: SRZ) has reported a materially higher Mineral Resource Estimate (MRE) for the Severn Deposit at its Heemskirk Tin Project in western Tasmania. The updated estimate lifts total Severn resources by 64% to 8.54Mt at 0.82% tin for 70,002t of contained tin. The most important shift in the ASX announcement is the increase in geological confidence, with the Indicated Resource up 125% to 6.05Mt at 0.84% tin for 50,739t of contained tin.

According to the ASX announcement, the Severn update lifts the total Heemskirk Tin Project resource to 13.36Mt at 0.86% tin for 115.3kt of contained tin. Including the nearby St Dizier satellite deposit, Stellar's total mineral resource base now stands at 15.6Mt at 0.83% tin for 129.1kt of contained tin.

For investors, this is more than a larger headline tonnage figure. The updated resource increases the share of higher-confidence material that can support mine planning and the ongoing Pre-Feasibility Study (PFS), which the company said it expects to complete in Q3 2026.

"This updated Mineral Resource Estimate is another milestone for Stellar, boosting the scale and confidence of the Heemskirk Tin Project," said Simon Taylor, Managing Director and CEO. "With over 129,000 tonnes of contained tin now defined across our asset base and two drill rigs continuing to test immediate growth targets, Stellar is exceptionally well-positioned to capitalise on the structural supply deficits driving the global tin market."

What Changed at Severn?

The updated MRE was completed by independent technical consultant Haren Consulting and incorporates 18 new diamond drill holes and wedges for 5,861 metres completed since the prior 2023 Severn estimate.

The direct comparison in the ASX announcement shows the scale of the change:

The lower average grade in the 2026 reported resource reflects a lower 0.4% tin cut-off grade, compared with 0.6% tin in the 2023 estimate. Stellar said this change reflects a stronger tin price setting and inputs from the ongoing PFS.

Did the Resource Genuinely Improve?

That distinction matters. A lower cut-off grade can increase reported tonnes, so investors should ask whether the resource really improved or whether the reporting threshold simply changed.

The ASX announcement addresses that issue directly. On a like-for-like basis at the 0.6% cut-off, the 2026 Severn estimate still showed an 82% increase in contained tonnes and an 85% increase in contained tin within the Indicated category, with grade also rising by 0.02% tin. That suggests the uplift was not driven solely by a definitional change.

Heemskirk Resource Base Now Stands at 115,300 Tonnes of Tin

The Severn update feeds into a larger project-scale inventory across Heemskirk's Queen Hill, Severn and Montana deposits.

Across the wider asset base, the combined resource as reported by Stellar is:

One technical feature highlighted in the announcement is the high proportion of tin hosted in cassiterite, the main oxide mineral of tin. At Heemskirk, cassiterite accounts for 98% of total tin across the project resource, and 97.5% across the Indicated category.

This is potentially important because metallurgical test work cited by the company suggests the mineralisation may respond to conventional processing methods.

Why Does the Indicated Resource Increase Matter?

The headline tonnage increase is important. However, the rise in the Indicated Resource is arguably the more relevant development for project valuation.

Under the JORC Code (2012), mineral resources are grouped by confidence level:

• Inferred Resource: early-stage estimate with lower confidence
• Indicated Resource: better defined geology and grade continuity, suitable for mine planning studies
• Measured Resource: highest confidence category

At Severn, Stellar stated that material classified as Indicated generally has average drill spacing of around 25m by 25m. In practical terms, that means the deposit has been drilled closely enough in these areas to support a more reliable geological model.

Why This Matters to Investors

A larger Indicated Resource can improve the quality of a PFS because engineering designs, mine scheduling, and economic modelling can rely more heavily on better-defined material. That does not guarantee project economics, but it can reduce one layer of uncertainty.

Furthermore, the classification improvement at Severn followed infill and extension drilling that, according to the company, largely confirmed previous interpretations and improved confidence in both grade and geological continuity.

What Is a Cut-Off Grade and Why Does It Affect Resource Size?

A cut-off grade is the minimum metal grade used to define whether material is included in a reported mineral resource. If the cut-off is lower, more rock may qualify as part of the resource. If the cut-off is higher, only better-grade material is included.

This is why resource comparisons need context. A project can show higher tonnage simply because the reporting threshold was reduced.

In Stellar's case, the Severn MRE was reported at a 0.4% tin cut-off in 2026 versus 0.6% tin in 2023. The company said this reflected:

• Stronger tin prices, which reached above US$50,000/t during 2026
• An exchange rate around $US/$A 0.70
• Current PFS mining and recovery inputs

The updated resource modelling also used a broader mineralised envelope incorporating material down to 0.1% tin. According to the announcement, that was done to support longer-range geological interpretation and assess the possible impact of ore sorting in the PFS.

What Is Ore Sorting?

Ore sorting is a process that separates lower-grade and higher-grade rock before the main processing plant, with the aim of improving feed quality and reducing waste treatment. It is still being assessed as part of the study work.

How Does Heemskirk Compare With Global Tin Development Peers?

Stellar stated in the announcement that Heemskirk remains the highest-grade undeveloped tin project in Australia and the third highest-grade globally of peer company projects.

The company provided the following peer comparison table based on publicly available disclosures:

These comparisons should be treated carefully. Stellar included a cautionary statement in the ASX announcement noting that peer projects may not be directly comparable because of differences in development stage, cut-off grades, mineralogy, metallurgical assumptions, and reporting methods.

Even with that caveat, Heemskirk's combination of grade and scale stands out in the peer set. For development assets, higher grade can be important because it may support better margins if mining and processing assumptions hold up in later studies.

PFS and Drilling Remain the Next Catalysts

The announcement makes clear that the resource is not the final word on Heemskirk. Two drilling rigs remain active, with current work focused on:

• The Montana Resource
• Depth extensions at Severn
• Untested new targets generated from geological modelling

Severn itself remains open down-dip and down-plunge, with the company describing a down-dip extent of over 700 metres.

What Will the PFS Cover?

At the same time, the company expects to complete the Pre-Feasibility Study in Q3 2026. According to the announcement, the PFS is considering:

• Underground mining via long hole open stoping
• Metallurgical processing through standard crushing, grinding, sulphide flotation, and gravity separation
• Ore sorting impacts
• Updated resource information from the new MRE

The metallurgical test work cited in the release suggests a 48% tin concentrate with 73% recovery may be achievable, although this remains part of the broader study process rather than a final operating outcome.

In addition, environmental baseline work is ongoing, and the company noted that a mining licence for tailings storage has already been granted by Mineral Resources Tasmania.

What Does the Announcement Mean for Investors?

This ASX update strengthens Stellar's position as a development-stage tin company with a larger and better-defined flagship resource.

The main investor takeaways from the announcement are clear:

1. Severn has grown materially, with contained tin increasing to 70,002 tonnes
2. Confidence has improved sharply, with Indicated tin at Severn rising to 50,739 tonnes
3. Heemskirk now holds 115,300 tonnes of contained tin, rising to 129,100 tonnes across the total asset base including St Dizier
4. Further growth drilling is ongoing, which leaves room for additional resource updates
5. The PFS in Q3 2026 is set to be the next major technical and valuation milestone

The resource update does not by itself confirm project economics or development timing. Those questions will be tested more directly in the PFS. However, what the announcement does show is that the geological base for that study is now larger and carries higher confidence than before.

For a tin-focused ASX company, that is a material development.

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