Sunstone Metals (STM) investor relations material

Project highlights and economics

• Bramaderos scoping study shows an after-tax NPV of US$0.9B (base case) to US$2.7B (spot), with IRRs of 28% and 50%, a 19-34 month payback, and a 23-year mine life.

• Initial production averages 135,000 oz/year for the first 8 years, with all-in sustaining costs of US$1,499/oz and a low strip ratio of 1.4.

• CapEx is estimated at US$511M, with construction expected to take 18 months and production targeted for 2031.

• Life-of-mine post-tax free cash flow is estimated at US$2.4B (base case), with project economics most sensitive to gold price.

• Project benefits from strong infrastructure, community support, and minimal environmental or social obstacles.

Resource growth and expansion potential

• Current Mineral Resource Estimate is 3.6Moz AuEq at 0.5g/t, with drilling underway aiming for at least 5Moz in 2026 and long-term potential of 10Moz+.

• Exploration Target of 5.0–13Moz AuEq, with expansion possible to 20–30Mtpa throughput and annual production scaling to 300,000–400,000 oz.

• Resource growth focused at Melonal, Copete, and Porotillo, with further upside from additional porphyry and epithermal targets.

• Limon deposit not included in current study but represents future upside pending further drilling and resource definition.

• Resource conversion from Inferred to Indicated is considered highly probable due to porphyry geology.

Mining, processing, and cost structure

• Open-pit mining with contractor-operated trucks and shovels, minimal pre-strip, and staged mining capacity up to 55Mtpa.

• Processing plant designed for 10Mtpa, using SAB grinding, flotation, and CIP leach, with gold recovery averaging 85% and copper 75%.

• Operating costs benchmarked against similar jurisdictions; low energy and labor costs in Ecuador.

• Waste management includes encapsulation of acid-forming material and use of mine waste for TSF construction.

• Flow sheet similar to Boddington and Telfer, with potential for further cost optimization.