Bramaderos Resource Growth Hinges on Pending Porotillo Assays

Porotillo Drilling Confirms Resource Expansion Potential

Sunstone Metals Ltd (ASX:STM) has reported continued success at its Bramaderos gold-copper project in southern Ecuador, with the latest two drill holes at the Porotillo target intersecting substantial mineralisation outside the existing 3.6Moz resource. Hole PTDD004, the first drilled into Porotillo’s north-west domain, returned a standout 116m at 0.57 g/t AuEq, including 20m grading 0.91 g/t AuEq, while PTDD005 added 99m at 0.33 g/t AuEq. These results reinforce the company’s strategy to convert a large Exploration Target of 1.7 to 3.5Moz AuEq within the Copete-Porotillo cluster into a JORC-compliant resource.

The Porotillo system, adjacent to the pit-constrained Bramaderos Mineral Resource, has been a focus of Sunstone’s 5,000m diamond drill program, which now has 16 of 28 planned holes completed. Assays for several holes remain pending, but the consistent long intersections so far provide confidence in the geological interpretation and resource growth potential. This drilling momentum builds on earlier results at Bramaderos, including strong intersections at Copete and Melonal, underscoring the project's expanding footprint and mineralisation continuity. The company’s approach reflects a detailed understanding of the controls on mineralisation and the geometry of the porphyry systems, placing it in an exploration sweet spot where drilling returns have been particularly encouraging. The ongoing program aims to deliver a significant resource upgrade ahead of a planned update later in 2026, a key milestone for the project’s development trajectory.

Geological Insights and Mineralisation Characteristics

Detailed logging and assay results from Porotillo holes reveal a complex high-level carapace of porphyry stocks, characterised by multiple generations of intrusion breccias overprinted by stockwork veining. Copper mineralisation is dominated by chalcopyrite and bornite of hypogene origin, with supergene minerals such as chalcocite and native copper also present. The mineralised intervals are accompanied by elevated silver and molybdenum, consistent with typical porphyry systems. A cross-section through PTDD004 and nearby holes highlights the extensive magnetic anomaly associated with potassic alteration and secondary magnetite, which is guiding further drill targeting. The company’s sampling and assay protocols adhere to industry standards, with robust QAQC measures ensuring data reliability. While true widths of mineralisation are yet to be determined, the downhole intercepts provide a strong basis for resource modelling and expansion.

Strategic Positioning and Project Outlook

Bramaderos boasts a current Mineral Resource estimate of 220Mt at 0.50 g/t AuEq for 3.6Moz AuEq, with exploration targets indicating potential to more than double this. The Copete-Porotillo exploration target alone is estimated at 135–180Mt grading 0.40–0.60 g/t AuEq, representing 1.7 to 3.5Moz AuEq. Sunstone’s Managing Director Patrick Duffy emphasises the scarcity of undeveloped gold-copper projects of this scale in such a favourable location, highlighting Bramaderos’ rapid growth outlook and strong infrastructure support. The project benefits from proximity to power, road, and port facilities, alongside committed community engagement and ESG practices detailed in the company’s inaugural Sustainability Report. Sunstone is concurrently advancing its El Palmar project in northern Ecuador, which holds a 1.2Moz AuEq resource and a substantial exploration target, positioning the company with a robust pipeline of gold-copper assets in Ecuador’s mineral-rich belt.

Sunstone’s ongoing drill campaign and resource conversion efforts follow a series of recent announcements outlining strong drilling results and strategic updates. The company has recently extended Bramaderos Resource with wide gold-copper intersections and is working to upgrade resource classifications after retracting production targets due to reliance on inferred resources amid resource classification concerns. These developments frame the current drilling as part of a broader push to solidify Bramaderos’ economic potential ahead of a resource update later this year.

Next Steps in Drilling and Resource Definition

With several holes still awaiting assay results and a second phase of drilling planned to target deeper magnetic bodies beneath shallow mineralisation, Sunstone’s exploration program remains dynamic. The company is progressively optimising drilling plans based on incoming data and geological modelling. The focus is now on infilling and expanding the resource footprint to underpin future scoping and feasibility studies. Funding availability will be a critical factor in sustaining this momentum over the next two years, as Sunstone balances aggressive exploration with strategic capital management. Investors will be watching closely as assay results from the remaining holes and the forthcoming resource update provide clearer insights into Bramaderos’ scale and grade potential.