Greatland Unveils 70Mt High-Grade Tungsten Resource at O’Callaghans

A Globally Significant Tungsten Asset

Greatland Resources Limited (ASX:GGP) has announced a substantial Mineral Resource Estimate (MRE) for its O’Callaghans deposit in Western Australia, highlighting the project as one of the largest high-grade tungsten resources worldwide. The deposit, containing 70 million tonnes grading 0.35% tungsten trioxide (WO3), also hosts notable quantities of copper, zinc, and lead, underscoring its polymetallic nature.

Situated just 10 kilometres south of Greatland’s flagship Telfer mine, O’Callaghans benefits from proximity to existing infrastructure, potentially reducing future development costs and timelines. The resource is predominantly classified as Indicated, reflecting a high degree of confidence supported by extensive drilling; over 71,000 metres across 184 drill holes; conducted primarily between 2008 and 2010.

Strategic Importance Amid Market Dynamics

Tungsten is recognised globally as a critical mineral, essential for applications demanding extreme hardness and high melting points, such as aerospace, defence, and industrial manufacturing. The market has experienced significant upheaval following China’s 2025 export controls, which have tightened supply and driven prices for ammonium paratungstate (APT) to approximately US$2,200 per metric tonne unit; a fivefold increase since early 2025.

Despite this, Greatland’s MRE conservatively values tungsten at US$450/MTU, a prudent approach that underscores the robustness of the resource estimate under current economic assumptions. This conservative pricing suggests substantial upside potential should market prices remain elevated or increase further.

Technical Foundations and Historical Context

The O’Callaghans deposit has a rich exploration history, with prior ownership by Newcrest Mining Limited, which completed a Pre-Feasibility Study (PFS) in 2014. This study demonstrated the technical and economic viability of a long-life underground mining operation employing long-hole open stoping and truck haulage, supported by a standalone processing facility and an APT plant for tungsten concentrate refinement.

Metallurgical test work underpins recovery assumptions of 70% for tungsten, 82.4% for copper, 76.2% for zinc, and 70.4% for lead, which have been incorporated into the net smelter return (NSR) calculations that inform the resource classification. The deposit’s geology is characterised by a flat, disc-shaped polymetallic skarn mineralisation zone approximately 350 metres below surface, with tungsten hosted in scheelite and wolframite minerals.

Looking Ahead: Optionality Within Greatland’s Portfolio

Greatland’s Managing Director Shaun Day emphasised the latent value of O’Callaghans within the company’s portfolio, particularly given the strong tungsten market conditions. While the company’s primary focus remains on its Telfer and Havieron projects, O’Callaghans presents optionality for future development and value enhancement, potentially leveraging synergies with Telfer’s existing infrastructure.

The announcement also reflects rigorous compliance with the JORC Code (2012 edition), with independent review by SRK Consulting affirming the reasonableness of the geological and estimation methodologies. This transparency and technical rigour provide investors with confidence in the resource’s reported scale and quality.