Sunstone Metals Extends Bramaderos Resource with Wide Gold-Copper Intersections

Widespread Mineralisation Beyond Current Resource

Sunstone Metals Ltd (ASX:STM) continues to push the boundaries of its Bramaderos gold-copper project in southern Ecuador, with the latest four drill holes delivering substantial mineralised intersections extending well beyond the existing 3.6 million ounce gold equivalent (AuEq) resource. Notably, these holes include a 250m intersection at the Melonal prospect and multiple wide zones at Porotillo, underpinning the company's strategy to convert a large exploration target into a defined resource.

All eight holes assayed in the current drilling campaign have returned significant mineralisation, a streak of success that bolsters confidence in the project's upside. The results confirm that the mineralised system remains open, particularly at Porotillo and Melonal, both adjacent to the pit-constrained Bramaderos Mineral Resource, suggesting ample room for resource expansion within this cluster.

Porotillo Drilling Highlights

At Porotillo, three holes have been completed with assays confirming continuous gold-copper mineralisation from surface to depths of up to 200m. Hole PTDD001 intersected 200.5m at 0.42 g/t AuEq, including a higher-grade 54.6m interval at 0.57 g/t AuEq. Similarly, PTDD002 and PTDD003 returned 140.4m at 0.45 g/t AuEq and 150.1m at 0.53 g/t AuEq respectively, with sub-intervals reaching up to 0.69 g/t AuEq near the end of the hole. These intersections correlate with extensive mineralisation identified in prior trenching programs, reinforcing Porotillo's potential to contribute meaningfully to the resource base.

The drilling at Porotillo is part of a 27-hole, 5,000m program that has now completed 14 holes, including earlier successful holes at Copete. This ongoing campaign aims to upgrade a significant portion of the Copete-Porotillo exploration target, which is estimated at 135–180 million tonnes grading 0.40–0.60 g/t AuEq for 1.7 to 3.5 million ounces AuEq. The company is methodically refining drilling plans as assay and geological data come in, indicating a dynamic and responsive exploration approach. This builds on the momentum from the company's strong Copete-Porotillo drilling results earlier in May.

Melonal Prospect Extends Mineralisation

The Melonal prospect delivered a standout intersection in hole MEDD003, which was terminated at 271m due to ground conditions but still managed to intersect 250.4m at 0.43 g/t AuEq from surface. This includes a higher-grade 44m interval at 0.73 g/t AuEq. Importantly, this mineralisation lies beyond the limits of the current resource model and extends well beyond the modelled open pit, indicating that Melonal remains open at depth and laterally to the south where no drilling has yet occurred.

This discovery highlights Melonal's potential as a key growth area within Bramaderos, complementing the Porotillo and Copete prospects. The geological setting, marked by a large magnetic anomaly and extensive vein stockworks, supports the interpretation of a robust porphyry system that could significantly add to the overall resource.

Strategic Resource Growth and Project Outlook

Sunstone's Managing Director Patrick Duffy emphasised that the new results align with the company's clear strategy to grow the 3.6Moz resource by converting the extensive exploration targets into defined resources. He noted the company has a strong grasp on the controls and geometry of mineralisation, placing it in an 'exploration sweet spot' with excellent returns from drilling.

The Bramaderos project benefits from excellent infrastructure, including proximity to power, roads, and ports, and enjoys solid community support with a commitment to ESG standards, as outlined in the company's 2023 Sustainability Report. This infrastructure and social license underpin the project's potential to evolve into a multi-decade mining operation.

Sunstone is progressing studies towards development, with a scoping study released earlier this year demonstrating project viability and a post-tax NPV of US$0.9 billion. The company is concurrently managing a strategic process to determine optimal long-term funding to unlock value from Bramaderos and its other Ecuadorian asset, El Palmar.

Despite the promising drilling results and growth potential, the exploration targets remain conceptual with inherent uncertainty about converting all targets into resources. The company plans a resource update later in 2026, following completion of the current drill program and assay results. This update will be critical for investors to gauge the scale and quality of the resource expansion.

The drilling campaign and resource growth ambitions come in the wake of Sunstone's recent retraction of production targets due to reliance on inferred resources, underscoring the importance of upgrading resource classifications through infill drilling.