Sunstone Metals Expands Gold-Copper Resource with 296m at 0.43 g/t AuEq
Key Takeaways
- Hole MEDD004 returned 296.7m at 0.43 g/t AuEq from surface, including a high-grade sub-interval of 64.3m at 0.69 g/t AuEq — the strongest result yet from the Melonal porphyry system.
- All results sit outside the existing November 2025 Mineral Resource Estimate of 220Mt at 0.50 g/t AuEq, directly signalling upward resource revision potential in the upcoming 2026 update.
- A second hole, MEDD006, added 102m at 0.52 g/t AuEq from surface, while Porotillo trenching extended the mineralised footprint with trench PO-8 returning 109.7m at 0.61 g/t AuEq.
- Sunstone has now drilled 28 mineralised holes across the Bramaderos porphyry cluster outside the current resource boundary, with a 100% hit rate across all five assayed Melonal holes.
- The 2026 Mineral Resource update — set to incorporate Melonal, Copete, and Porotillo for the first time — is the defining near-term catalyst, against a project-level Exploration Target of 4.1 to 11.2 Moz AuEq.
Melonal emerges as a large-scale gold-copper system with 296m at 0.43 g/t AuEq
Sunstone Metals (ASX: STM) has released the latest results from its highly successful 2026 drilling program at the Bramaderos Project in southern Ecuador, with assays from the Melonal porphyry system significantly expanding known mineralisation outside the existing 3.6 Moz AuEq Mineral Resource. The headline intercept from hole MEDD004 — 296.7m at 0.43 g/t AuEq from surface — is the defining result of the 3 September 2026 announcement, confirming Melonal as a system of genuine scale. These results sit outside the November 2025 Mineral Resource Estimate (MRE) of 220Mt at 0.50 g/t AuEq, pointing to meaningful resource growth potential ahead of the 2026 update.
MEDD004’s headline intercept includes high-grade sub-intervals of 64.3m at 0.69 g/t AuEq from surface and 82.3m at 0.50 g/t AuEq from 83.7m. A second hole, MEDD006, returned 102m at 0.52 g/t AuEq from surface, including 48.5m at 0.62 g/t AuEq from surface.
Patrick Duffy, Managing Director, Sunstone Metals
“These latest drill holes show Melonal is fast emerging as a large-scale mineralised system. Modelling is ongoing and points to significant depth extensions of the system towards the south and southeast.”
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Drilling and trenching results at Melonal and Porotillo
Melonal drill hole performance
MEDD004 and MEDD006 were drilled from a common collar at the southern end of Melonal, along with MEDD003 and MEDD007, as a fan of four holes drilled at different azimuths into the southern end of the system. The holes were designed to test below and beyond the planned southern pit wall as modelled from the November 2025 MRE. Assays from MEDD003, MEDD004, and MEDD006 have confirmed substantial mineralisation sitting below and south of that planned pit wall. Importantly, all five assayed Sunstone holes at Melonal across the 2022 and 2026 programs have returned mineralised results — a 100% hit rate. Two holes, MEDD005 and MEDD007, are still awaiting final assays.
| Drill Hole | Interval (m) | AuEq (g/t) | Au (g/t) | Cu (%) |
|---|---|---|---|---|
| MEDD001 | 266 | 0.36 | 0.22 | 0.08 |
| MEDD002 | 239.5 | 0.38 | 0.24 | 0.08 |
| MEDD003 | 250.45 | 0.43 | 0.25 | 0.11 |
| MEDD004 | 296.65 | 0.43 | 0.25 | 0.11 |
| MEDD004 (incl.) | 64.3 | 0.69 | 0.37 | 0.19 |
| MEDD004 (and) | 82.3 | 0.50 | 0.30 | 0.12 |
| MEDD006 | 102 | 0.52 | 0.28 | 0.14 |
| MEDD006 (incl.) | 48.5 | 0.62 | 0.31 | 0.18 |
Porotillo trenching continues to deliver
Surface trenching at Porotillo represents a separate but complementary dataset to the drilling program, and the latest results continue to extend the mineralised footprint. New trench PO-8 returned 109.7m at 0.61 g/t AuEq, while trench PO-9 combined with channel CH-3 returned 39.3m at 0.42 g/t AuEq. Earlier trenches PO-5, PO-6, and PO-7 combined for an impressive 698m at 0.52 g/t AuEq. The announcement notes that mineralisation at Porotillo remains open on several sides.
The Porotillo gold-copper discovery was first reported in August 2026, when initial trench results confirmed a separate but structurally related mineralised system within the broader Bramaderos porphyry cluster, establishing Porotillo as a genuine complement to the Melonal resource.
Assay results are still pending for a number of items that will feed into the upcoming resource update:
- Two additional Melonal drill holes (MEDD005 and MEDD007)
- Completion of channel assaying at Melonal surface
- Assays from trenches PO-10 to PO-14 at Porotillo, with visual observations of porphyry-related quartz stockwork veins already noted in PO-13 and PO-14
What is a porphyry gold-copper system, and why does scale matter?
Porphyry deposits are large, low-grade, bulk-tonnage mineral systems that host a significant share of the world’s copper and gold production. They are typically mined at high volumes over many decades, meaning scale and continuity of mineralisation are the defining economic criteria — not just peak grade.
AuEq, or gold equivalent, is a single metric that combines gold, copper, and silver values into a comparable figure using commodity prices and recovery estimates. It allows investors to assess the overall economic value of a mineralised system across multiple metals in one number.
One feature of the Melonal results that carries particular weight is that the main intercept of 296.7m starts at surface. Mineralisation that begins at surface reduces the amount of waste material that must be removed before ore can be mined — a measure known as strip ratio. Lower strip ratios generally support stronger open-pit economics. When a system delivers long intercepts from surface, it signals a deposit that could be mined more cost-effectively.
Equally significant is where this mineralisation sits: outside the existing 3.6 Moz AuEq Mineral Resource boundary. That matters because Melonal, Porotillo, and Copete are three of five deposits within the Bramaderos central porphyry cluster that are currently excluded from the existing resource. The upcoming 2026 Mineral Resource update will incorporate all three, meaning the resource base could grow materially from a baseline that does not yet reflect the full extent of the known system.
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Resource update on the horizon as Bramaderos growth case builds
The 2026 Mineral Resource update is the near-term event that ties these results together, and this announcement materially strengthens the case for a larger resource number. The Bramaderos Project carries a Porphyry Exploration Target of between 4.1 Moz and 11.2 Moz AuEq within 315 to 505 Mt at a grade between 0.41 and 0.68 g/t. It is important to note that this Exploration Target is conceptual in nature. There has been insufficient exploration to estimate a Mineral Resource for these target areas, and it is uncertain whether further exploration will result in the estimation of a Mineral Resource.
What is not conceptual is the drilling momentum behind these results. A total of 28 mineralised holes have now been drilled within the cluster of porphyry systems outside the current Bramaderos Mineral Resource — a strong signal of consistent, systematic discovery across the broader project area.
Key upcoming catalysts to watch, in order:
- Assays from MEDD005 and MEDD007 at Melonal
- Completion of channel assaying at the Melonal surface
- Assays from trenches PO-10 to PO-14 at Porotillo
- Bramaderos 2026 Mineral Resource update, incorporating Melonal, Copete, and Porotillo
- Resumption of drilling at the El Palmar Project, expected in September 2026
Each of these catalysts has the potential to add further definition to a system that is clearly larger than the current resource reflects. The Melonal results alone confirm that the southern extension of the porphyry plunges beyond the current pit design — and modelling of that depth extension is still ongoing.
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