Sunstone’s Porotillo assays point to another Bramaderos growth zone

Porotillo assays extend Sunstone’s resource-growth narrative

Sunstone Metals Ltd (ASX:STM) has finished the latest stage of surface sampling at Porotillo in southern Ecuador with a set of broad, coherent-looking gold-copper intervals that support further work beyond the current pit-constrained resource. The standout result was 126.32 metres at 0.41 g/t AuEq from trench PO-16a, alongside 95.50 metres at 0.50 g/t AuEq from PO-15 and 97.58 metres at 0.44 g/t AuEq from PO-10c.

“Trenching at Porotillo”

The strongest average grade among the newly reported intervals came from PO-10b, which returned 30.38 metres at 0.64 g/t AuEq. Sunstone also reported 89.56 metres at 0.47 g/t AuEq from PO-10d. Those results sit across different parts of the Porotillo target, but the company cautions that separate trench lines have not been combined and that continuity between them has not been assumed.

Results add surface evidence around a 6.2Moz resource

“Plan view of the central porphyry cluster at Bramaderos showing the October 2026 MRE pit outlines (blue), drillhole AuEq assays and gold-in-soil shading.”

The assays arrive shortly after the October Bramaderos resource upgrade, which lifted the project’s Mineral Resource Estimate by 72% to 6.2 million ounces of gold equivalent across 464 million tonnes. Porotillo was incorporated into that estimate alongside Copete after a 20-hole, 3,866-metre diamond drilling program followed the initial trenching campaign.

Earlier Porotillo trenching had already produced long intervals, including 462.22 metres at 0.55 g/t AuEq from PO-5 and 109.74 metres at 0.61 g/t AuEq from PO-8. The latest results extend the surface sampling sequence from PO-10 to PO-17 and include channel sample PC5. Sunstone says the mineralisation is mainly hosted by quartz diorite and intrusive breccia, with vein styles and magnetite consistent with a porphyry system.

Copper anomaly opens a second Porotillo target

The company is not limiting its next steps to the mineralised ground already tested. Gridded soil data shows a broad copper-in-soil anomaly south of Porotillo Hill, extending beyond the area of stronger gold-in-soil values. Sunstone is assessing short reconnaissance trenches across the stronger copper zones, which remain untested by trenching or drilling.

“Existing gridded soil geochemistry also indicates a broad area of strong copper anomalism extending south of Porotillo Hill beyond the area of significant gold-in-soil values…”

Caption and image © Sunstone Metals Ltd. From “Trench results point to potential Bramaderos resource growth”, 4 Nov 2026.

At the same time, eight trenches with a combined planned length of about 844 metres are being excavated between the Copete and Melonal porphyry centres. The program targets mapped diorite outcrops along an approximately 650-metre trend, where magnetic responses, anomalous gold-copper-molybdenum rock chips and stockwork-style veining coincide. Results are expected only after the work and assay interpretation are complete.

Exploration upside still carries important limits

Sunstone frames Bramaderos as having substantial additional exploration potential, but its exploration target remains conceptual and is not a Mineral Resource. The announcement also presents differing Bramaderos exploration-target figures in separate sections, citing 4.4 million to 11.2 million ounces AuEq in the headline discussion and 3.5 million to 9.5 million ounces in the company overview. That discrepancy will need to be reconciled.

There is also a technical caveat in the filing’s JORC appendix: several sampling and assay sections contain instructions to confirm or insert laboratory, preparation and quality-control details before release. The headline trench results are therefore useful as exploration evidence, not as proof that the system can be converted directly into additional tonnes, mineable grades or economic value.