Sunstone’s Bramaderos Scoping Study Highlights US$0.9B NPV and 23-Year Mine Life

Robust Economics Underpin Long-Life Gold-Copper Operation

Sunstone Metals (ASX:STM) has unveiled a Scoping Study for its Bramaderos Gold-Copper Project in southern Ecuador that paints a compelling picture: a 23-year mine life delivering an average of 135,000 gold-equivalent ounces annually for the first eight years, at an all-in sustaining cost (AISC) of US$1,499 per ounce. The study estimates a post-tax net present value (NPV) of US$0.9 billion at a conservative gold price of US$3,500/oz, swelling to US$1.9 billion at the current spot price of US$5,000/oz.

With an initial capital outlay of US$511 million, the project promises a swift payback period of 34 months under base case assumptions, shrinking to 19 months at spot prices. Sunstone’s Managing Director Patrick Duffy emphasised the strong financial returns driven by low operating costs, solid production rates, and the project's 23-year horizon. "This is just the beginning," he noted, pointing to significant exploration upside yet to be factored into the economics.

Strategic Location and Low-Cost Operating Environment

The Bramaderos Project benefits from a cluster of five near-surface porphyry systems, including Brama-Alba and Melonal, accessible via sealed roads off the Pan-American Highway. The site enjoys ready access to water from the Rio Catamayo, grid power with a renewable and LNG mix, and proximity to international ports at Puerto Bolivar and Guayaquil. These factors combine to keep development capital and operating costs competitive.

Notably, Ecuador’s cost environment stands out with labour and energy expenses significantly below those in Australia, Canada, and the US. This cost advantage underpins the project’s low mining cost benchmarked at US$2.39 per tonne and processing costs of US$10.02 per tonne, verified by Tier-1 engineering firm Ausenco.

Resource Base and Exploration Upside

The Scoping Study hinges on the November 2025 Mineral Resource Estimate (MRE) of 3.6 million ounces gold-equivalent (AuEq) within 220 million tonnes at 0.5g/t AuEq. Of this, 20% is classified as Indicated Resources and 80% as Inferred, with the study prioritising Indicated material in the initial years to demonstrate economic viability. The project’s low geological risk is bolstered by the porphyry deposit’s continuous mineralisation patterns, which historically allow efficient conversion of Inferred to Indicated Resources.

Beyond the current resource, Sunstone has identified a substantial Exploration Target ranging from 5.0 to 12.9 million ounces AuEq across 345 to 549 million tonnes, covering extensions at Brama-Alba, Melonal, Copete-Porotillo, and the Limon epithermal system. These targets remain conceptual but represent a significant runway for resource growth and potential Stage 2 mine expansion to 20-30Mtpa throughput, funded from operating cash flows once production commences.

This exploration potential is underscored by recent drilling campaigns, including wide gold-copper zones at Bramaderos that are actively expanding the resource base and feeding into the project’s evolving economic model. The company’s ongoing 26-hole, 5000m program focuses on the Copete-Porotillo porphyry complex, a key growth area within the broader project footprint.

Processing and Environmental Considerations

The processing plant design features a conventional single-line SAG/Ball mill flotation and cyanide leach circuit, targeting recoveries of 85% for gold and 75% for copper. The facility’s 10Mtpa capacity aligns with the mine plan, with scope for future expansion. Tailings and waste management plans include encapsulation of potentially acid-forming materials and utilization of on-site storage facilities, reflecting a commitment to environmental compliance and social licence.

Sunstone’s community engagement and sustainability efforts are highlighted as integral to project development, with local support and environmental monitoring programs in place. The project’s location avoids environmentally sensitive areas and benefits from existing infrastructure, reducing permitting complexity.

Funding and Next Steps

To realize the Bramaderos Project’s potential, Sunstone anticipates raising approximately US$525 million through a combination of debt, equity, or strategic partnerships. The company is preparing to advance to Pre-Feasibility and Optioneering Studies alongside ongoing exploration drilling aimed at resource conversion and expansion.

Critical milestones include securing environmental approvals, finalizing project financing, and progressing construction and commissioning activities. The company’s experienced management team, with a track record in mine development and capital markets, positions it well to navigate these phases.

Given the project's strong economics and substantial upside, market watchers will be keen to track Sunstone's progress through the Pre-Feasibility Study and forthcoming drilling results that could further enhance the project’s scale and value.