Great Southern Copper LON:GSCU is attempting to do what junior miners are meant to do, but rarely manage at pace: turn geological promise into something approaching scale.
The London-listed explorer has completed its most advanced drilling campaign to date at Cerro Negro in northern Chile, and the results so far suggest a mineral system that is growing in both depth and complexity rather than narrowing with investigation.
Phase III drilling at Cerro Negro, part of the wider Especularita project, comprised 17 diamond drillholes and six reverse circulation holes, totalling nearly 4,000 metres. It is the largest programme the company has undertaken and builds on earlier work that identified a high-grade copper-silver system at Mostaza, centred on the Mostaza Fault Zone. That structural corridor extends more than 2km south of the historic mine and is increasingly emerging as the backbone of the project’s exploration thesis.
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What Phase III appears to confirm is that mineralisation at Mostaza is not confined to a single lens. High-grade copper-silver Lens 2 has been extended both at depth and along strike, and the company now believes multiple stacked lenses may be present. This matters. Stacked sulphide systems can materially change the economics of a project, turning what might otherwise be a narrow, high-grade curiosity into a deposit with continuity and optionality.
Great Southern Copper’s eye-catching assays
Previously released assays underline the point. Intercepts approaching 10 per cent copper with silver grades well above 700g/t are eye-catching by any standard, even if they occur over sub-metre widths. More relevant for valuation is the presence of broader zones grading 1–3 per cent copper with strong silver credits, suggesting that high-grade shoots sit within a more extensive mineralised envelope.
Phase III drilling also delivered something genuinely new: the identification of a base metal silver-lead-zinc lens in the Lens 2 area. While not the company’s primary focus, this adds another layer to the geological story and supports the idea of a multi-phase hydrothermal system. Meanwhile, reverse circulation drilling along the fault zone intersected both oxide and sulphide mineralisation, reinforcing the view that the MFZ could host a much larger system than initially recognised.
Assays for several diamond holes and all RC holes are still pending. In junior mining terms, this keeps the near-term newsflow intact and gives management flexibility in designing the next drilling phase. Planning is already under way, with follow-up work envisaged not only at Mostaza but also at the Monolith zone and along further stretches of the fault system.
Cerro Negro is not the only card in the deck
At Viuda, another discovery made during 2025, the company is targeting a large gold-copper porphyry system with similarities to those found in Chile’s prolific Maricunga belt. Ground geophysics is in progress ahead of further drilling. Further south, the Colorada lithocap represents a district-scale copper-gold opportunity that has yet to be drill tested, offering classic exploration optionality.
Geography works in the company’s favour. Especularita sits at low elevation with good access to infrastructure and mining services, reducing some of the logistical friction that often plagues Andean exploration. Great Southern Copper also holds the option to acquire 100 per cent of the project, including the Mostaza mine, simplifying any future development pathway.
The broader backdrop is supportive. Copper, gold and silver prices remain elevated, and strategic interest in copper supply continues to grow as electrification accelerates. For now, Great Southern Copper remains firmly in the exploration camp, with no resource estimate and no production timetable. But Phase III suggests it is moving from discovery towards definition.
For investors, the attraction lies in momentum. Two discoveries in a year, expanding geological confidence, and multiple drill-ready targets give the company a pipeline rather than a single bet. The risk, as always, is that continuity disappoints or grades dilute with scale. The opportunity is that Cerro Negro proves to be not just high grade, but materially large.
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