Bramaderos metallurgical tests - additional information

Key points

• Significantly higher copper and gold recoveries compared to previous studies
• Average recoveries increased to 80% for copper and 93% for gold
• Positive impact on project metrics, including production, costs, and NPV

Full summary

Sunstone Metals Limited (ASX: STM) announced improved metallurgical results from its Bramaderos Gold-Copper Project in southern Ecuador. The latest tests show average recoveries of 80% for copper and 93% for gold, significantly higher than the 75% and 85% used in the April 2026 Scoping Study. These results are expected to positively impact key project metrics, including potential gold and copper production, unit costs, and NPV. The improved recoveries are attributed to the successful application of conventional flotation processing to both principal ore types within the Bramaderos resource. The metallurgical characteristics support a conventional processing flowsheet comprising crushing, grinding, flotation, and cyanidation of flotation tails to produce a copper-gold concentrate and gold dore. Discussions with offtake providers confirmed Bramaderos concentrate would be in high demand and receive favourable pricing terms.

Outlook

The improved metallurgical results provide a robust foundation for ongoing project studies and support the continued advancement of Bramaderos as a potential large-scale gold-copper development opportunity.