Greatland Resources Ltd (AIM:GGP, OTC:GRLGF, FRA:G8G, ASX:GGP) has delivered a major uplift at its flagship Telfer gold-copper operation in Western Australia, expanding the mineral resource by 150% to 8.0 million ounces (Moz) of gold and materially strengthening the project’s long-term production outlook.
The updated December 2025 Group Mineral Resource Estimate also takes the combined Telfer and Havieron resource to 14.9Moz of gold and 645,000 tonnes of copper, also providing a maiden mineral resource for the company’s 100%-owned O’Callaghans tungsten-copper-zinc-lead deposit, underscoring the scale of Greatland’s growing footprint in the Paterson Province.
The increase follows an aggressive drilling campaign through 2025, with more than 134,000 metres completed and a further 100,000 metres planned, supporting both resource growth and a significant upgrade in geological confidence.
Telfer December 2025 Mineral Resource (schematic).
Resource growth driven by Telfer expansion
Telfer was the clear driver of the update, adding 4.8Moz of gold at a discovery cost of around US$5 per ounce, taking the total resource to 8.0Moz.
Telfer December 2025 Mineral Resource Statement.
Crucially, the higher-confidence Measured and Indicated (M&I) category grew 163% to 3.8Moz, providing a stronger foundation for mine planning and conversion into reserves.
The resource spans multiple mining areas, reflecting the breadth of mineralisation across the operation:
- West Dome Open Pit: 4.9Moz gold, up 135%
- Main Dome Underground: 2.2Moz gold, up 225%
- West Dome Underground: maiden 0.6Moz gold resource
- Stockpiles: 0.3Moz gold
This combination of open pit, underground and near-mine resources highlights Telfer’s expanding inventory and operational flexibility.
Higher-grade underground opportunities take shape
A key theme emerging from the update is the growing importance of higher-grade underground zones.
The newly defined West Dome Underground (WDU) resource totals 0.6Moz at grades of around 2.3 g/t gold, marking a new potential mining front within the broader Telfer system.
The WDU is considered geologically analogous to the existing Main Dome Underground operation and remains open in multiple directions, with ongoing drilling targeting both extensions and resource upgrades.
West Dome Underground December 2025 Mineral Resource (isometric view).
At Main Dome Underground, continued growth in active mining areas and the inclusion of the Vertical Stockwork Corridor added further scale, with underground grades materially higher than those seen in the open pit.
This shift towards higher-grade material is expected to play an increasingly important role in future mine planning and production profiles.
Main Dome Underground December 2025 Mineral Resource (isometric view).
Infrastructure supports long-term production profile
The expanded resource base reinforces the long-term viability of Telfer’s existing infrastructure, including its 20-million-tonnes-per-annum (Mtpa) processing plant and established underground mining systems.
West Dome Open Pit continues to provide the baseload feed for the operation, with a large Indicated resource supporting near-term production and future reserve conversion.
West Dome Open Pit 2025 Mineral Resource.
At the same time, the company is targeting increased utilisation of underground infrastructure, where higher grades offer the potential to lift overall head grades and improve margins.
Building a multi-decade mining hub
Managing director Shaun Day said the scale and quality of the updated resource strengthens the case for Telfer and Havieron to operate as a long-life, integrated mining hub.
“Telfer and Havieron’s combined resource… has the potential to underpin a multi-decade, world class mining hub,” Day said.
“This strong resources update has been delivered by Greatland’s dedicated technical team who have executed an accelerated and extensive Telfer drilling program since taking ownership in December 2025,” he added. “The significant growth in Measured and Indicated resources, particularly at the West Dome Open Pit, is very pleasing, with this material being of adequate geological confidence to be evaluated as part of our upcoming ore reserve estimate.”
The company is now prioritising higher-grade opportunities, including further development of West Dome Underground and potential expansion of underground mining at Main Dome.
Next steps: Reserves update and continued drilling
With a significantly larger and more robust resource now defined, Greatland’s next key milestone will be an updated ore reserve estimate for Telfer, targeted for release in the June 2026 quarter.
Ongoing drilling will focus on converting Inferred material into higher-confidence categories and extending mineralisation across key zones, with further resource updates expected as new data is incorporated.
The combination of scale, improving confidence and growing higher-grade opportunities positions Telfer as a central pillar in Greatland’s broader strategy to build a long-life gold-copper business in Western Australia’s Paterson Province.