Great Southern Copper PLC (LON: GSCU) has reported a year of significant exploration progress at its Especularita copper-gold-silver project in Chile, with successive drilling campaigns confirming high-grade mineralisation at Mostaza and opening up broader district-scale porphyry potential.
For the year ended 31 March 2026, the company completed three phases of drilling at the Mostaza mine, with all 25 holes across the first two phases intersecting the target mineralised zone.
The strongest Phase I result came from hole CNG25 DD007, which returned 33 metres grading 1.96% copper and 60.6 grams per tonne silver from 87 metres, including individual assays of up to 16.15% copper and 646g/t silver.
Phase II drilling comprised 16 holes for 1,701.7 metres and returned grades of up to 10.4% copper and 672g/t silver. The programme identified a previously unrecognised near-surface mineralised body beneath the historical workings, with grades exceeding those of the previously mined lenses.
The larger Phase III campaign comprised 17 diamond holes for 2,923 metres and six reverse-circulation holes for 1,032 metres, returning grades of up to 9.76% copper and 778g/t silver.
Great Southern Copper said the drilling extended the high-grade Lens 2 mineralisation along strike and at depth while identifying a series of stacked copper-silver lenses within a broader system that thickens at depth.
Geophysical work also defined a 2.5-kilometre mineralised trend south of Mostaza, generating multiple new drill targets, while scout drilling extended mineralisation by as much as 1.5 kilometres along strike.
At the nearby Monolith target, rock sampling returned grades of up to 271g/t silver and 2.05% copper, with the mineralised footprint subsequently expanded to around 700 metres by 400 metres.
The company also confirmed a near-surface porphyry gold discovery at the Viuda prospect, described as the first recognised occurrence of this mineralisation style in Chile’s coastal belt. Sampling at Viuda Negra returned grades of up to 4.2g/t gold, 145g/t silver and 0.56% copper.
Post-period work has included further drilling across four porphyry copper targets, expansion of the company’s ground position at the La Colorada lithocap, and geophysical surveys designed to identify buried porphyry systems.
Great Southern Copper raised £2.5 million in November 2025, its largest fundraising since listing, to support the expanded exploration programme.
Chief executive Sam Garrett said the year had been transformational, with Mostaza emerging as a potentially scalable high-grade copper-silver system while the wider Especularita project continued to demonstrate district-scale porphyry potential.
The company’s next phase will focus on a Phase IV drilling programme aimed at advancing Mostaza towards mineral resource definition while continuing to test additional targets across Especularita.
