Sunstone Metals Hits 26.6 g/t Gold in Final Holes as Resource Update Nears

Final two holes close out a perfect 30-hole program with standout grades

Sunstone Metals (ASX: STM) has completed its 30-hole resource growth drilling program at the Bramaderos gold-copper project in southern Ecuador, closing out the campaign with its most striking results yet. The final two holes delivered 6.0m grading 26.60 g/t gold equivalent (AuEq) within a 9.4m interval at 17.23 g/t AuEq, alongside a separate 368-metre continuous mineralised intersection at 0.45 g/t AuEq, all outside the existing 3.6 million ounce (Moz) AuEq resource. Every single one of the 30 holes intersected significant mineralisation outside that existing resource boundary, with a new resource estimate due in the coming quarter.

Managing Director Patrick Duffy

“With exceptional grades and an extremely wide mineralised intersection, these final two drill holes will make another substantial contribution to the impending resource update.

“The resource growth drilling program has been highly successful, successful, with hole int intersecting mineralisation with every every hole outside the existing resource.

“Trenching at the Porotillo porphyry within Bramaderos is reaching its final stages, and assays will be in shortly for an additional eight trenches at Porotillo.”

What the drill results reveal about Bramaderos

MEDD005 — a high-grade zone hiding between two giants

MEDD005 was collared at the northern edge of the Melonal porphyry system, in the space between the established Alba and Melonal systems. The upper portion of the hole returned a solid 171.65m at 0.43 g/t AuEq, but the real story was at depth.

Beneath the valley floor, roughly midway between Alba and Melonal, the drill struck a skarn-like high-grade zone. Native gold was visibly observed in the core. The intersection returned 9.35m at 17.23 g/t AuEq, with a higher-grade subdomain of 5.95m at 26.61 g/t AuEq and a peak gold assay of 55.9 g/t Au over 2m at 293–295m downhole. The lower 95m of the hole also showed notable molybdenum (Mo) anomalism of up to 205 ppm.

The geological signatures bear strong similarities to the high-grade zone previously intersected at Alba in drill hole BMDD012 in 2021 — 7.2m at 28.88 g/t Au within 29.2m at 7.68 g/t Au. Both occur in upper peripheral areas of their respective porphyry systems, suggesting additional high-grade zones may exist in inter-system corridors once infill drilling is undertaken. A follow-up hole, BMDD051, is planned from Alba’s southern margin drilling towards Melonal.

The high-grade gold discovery at Bramaderos has been building across successive drill campaigns, with earlier Alba system results establishing the geological template that the MEDD005 skarn-like zone now mirrors.

MEDD007 — 368 metres of continuous mineralisation

MEDD007 was drilled from the same collar as MEDD003, MEDD004, and MEDD006, at an azimuth of 150° and a dip of -42°. The purpose was to follow the Melonal syn-mineral diorite intrusion at a shallow down-plunge angle towards the southeast, a direction confirmed by recent 3D modelling to mirror the plunge of the Brama-Alba mineralisation.

The result was an intersection of 367.99m at 0.45 g/t AuEq through a sequence dominated by stockwork-veined diorite. This is a bulk-tonnage result that directly underpins resource growth at Melonal.

To put both holes in context: the high-grade zone in MEDD005 equates to 161 gram-metres (AuEq g/t x metres), essentially comparable to the full MEDD007 intersection of 166 gram-metres. Two very different styles of mineralisation, roughly equal in resource contribution terms.

The full Melonal drill hole summary is presented below.

Understanding porphyry gold-copper systems and why high-grade zones matter

For investors less familiar with the geology, a few concepts help explain why these results matter.

What a porphyry system is: A porphyry deposit forms when magma intrudes into the earth’s crust, releasing hot, metal-rich fluids that deposit gold, copper, and silver into surrounding rocks as networks of veins and fine disseminations. They are the world’s most important source of copper and a major source of gold. Bramaderos hosts five distinct porphyry centres.

Why the space between systems can trap high grades: When porphyry-stage fluids encounter chemically reactive volcano-sedimentary wallrocks, gold can precipitate rapidly into a narrow, highly concentrated zone. This is rarer than the broad, lower-grade bulk of a porphyry body and considerably more valuable per tonne.

How gram-metres work as a comparison tool: Gram-metres (g/t multiplied by metres of intersection) allow investors to compare a narrow, high-grade hit with a wide, lower-grade intersection on the same basis. A 9.35m hit at 17.23 g/t and a 367.99m hit at 0.45 g/t look very different on the surface, but their gram-metre equivalents (161 and 166 respectively) tell you they contribute almost equally to the resource.

Why 30/30 holes hitting mineralisation matters: In resource estimation, continuity is everything. When every hole drilled in a campaign intersects mineralisation outside the existing resource boundary, it signals that the mineralised system extends well beyond what is currently counted. All 30 holes will feed into the 2026 Mineral Resource update. The direction of travel for the resource number is clear.

What comes next for Sunstone and the Bramaderos resource

The resource update is the central near-term catalyst. The 2026 Mineral Resource estimate is set for release in the coming quarter, incorporating all 30 holes from the recently completed resource expansion program across the Melonal, Porotillo, and Copete porphyry systems.

Beyond the resource update, the near-term pipeline includes:

• 2026 Mineral Resource update — due in the coming quarter
• Porotillo trenching assays — results pending for eight additional trenches
• Follow-up drill hole BMDD051 — planned from Alba’s southern margin, targeting the Alba–Melonal corridor
• New trenches at Melonal — planned approximately 300m southeast of Melonal over recently identified diorite outcrop
• El Palmar drilling — expected to recommence September 2026

Zooming out, the broader Bramaderos project sits within a substantial Exploration Target context. The Brama-Alba-Melonal corridor carries an Exploration Target of 2.4–7.7 Moz AuEq, while the Copete-Porotillo systems add a further 1.7–3.5 Moz AuEq. The overall Bramaderos porphyry Exploration Target spans 4.1–11.2 Moz AuEq.

It is important to note that these Exploration Targets are conceptual in nature. There has been insufficient exploration to estimate a Mineral Resource for the reported Exploration Target areas, and it is uncertain whether further exploration will result in the estimation of a Mineral Resource. What the targets do illustrate is the scale of the system Sunstone is working to delineate through its ongoing Ecuador strategy.

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