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NEWS RELEASE | 30 March 2026

December 2025 O'Callaghans Mineral Resource Statement

THIS ANNOUNCEMENT CONTAINS INSIDE INFORMATION AS STIPULATED UNDER THE UK MARKET ABUSE REGULATIONS.  ON PUBLICATION OF THIS ANNOUNCEMENT VIA A REGULATORY INFORMATION SERVICE, THIS INFORMATION IS CONSIDERED TO BE IN THE PUBLIC DOMAIN.

O'Callaghans - A globally significant Tungsten Resource

Mineral Resource Estimate for high grade 70Mt Tungsten-Copper-Lead-Zinc deposit

Greatland Resources Limited (Greatland or Company) (AIM:GGP, ASX:GGP) is pleased to provide a Mineral Resource Estimate (MRE) for the O'Callaghans tungsten-copper-zinc-lead deposit (O'Callaghans) as at 31 December 2025. O'Callaghans was previously reported as a Mineral Resource & Ore Reserve prior to Greatland ownership.

O'Callaghans is one of the largest high-grade tungsten deposits globally and benefits from significant copper, zinc and lead mineralisation. O'Callaghans is 100% owned by Greatland and located just 10km south of Telfer on a mining lease (M45/203) (Figure 1).

Key highlights:

§ Greatland MRE: 70Mt @ 0.35% tungsten trioxide (WO₃) / 0.30% Cu / 0.57% Zn / 0.28% Pb for 246Kt WO₃ / 207Kt Cu / 371Kt Zn / 182Kt Pb.

§ Globally significant strategic asset: O'Callaghans is one of the largest high-grade tungsten deposits globally (Figure 2). Tungsten is designated as a critical mineral by many countries including Australia, the United States, the European Union, Canada, the United Kingdom, Japan and India.

-  Tungsten's extreme melting point, hardness and density make it ideal and difficult to substitute for various applications including in mining, construction, automotive, aerospace, defence, industrial and chemical. Aerospace and defence applications currently account for ~25% of global tungsten demand.

China currently produces ~80% of global tungsten supply but imposed export controls on tungsten in early 2025. Historically a net exporter of tungsten, China became a very significant net importer of tungsten in 2025.

-  These and other geopolitical factors have contributed to a ~500% increase in benchmark pricing for Ammonium Para Tungstate (APT), a high purity tungsten compound, since February 2025, to ~US$2,200 per metric tonne unit (MTU; 1 MTU = 10kg). The O'Callaghans MRE uses pricing of US$450/MTU APT.

§ Work to date: O'Callaghans benefits from significant drilling and study work completed by previous owners.

-  The MRE is considered well informed with 71,000m of drilling from 184 drill holes (100m x 100m spacing) supporting the predominantly (>95%) higher confidence Indicated Mineral Resource.

-  Newcrest Mining Limited (Newcrest) historically reported an O'Callaghans Ore Reserve as recently as 2020, that was supported by a Newcrest 2014 Pre-Feasibility Study (PFS) that demonstrated a technically and economically viable long life mining operation. The PFS contemplated a long-hole open stoping with paste fill, utilising truck haulage and a standalone 2.0Mpta processing facility and APT plant.

- The PFS processing flowsheet was sequential flotation (copper, lead, zinc, and pyrite), followed by magnetic separation and gravity recovery of tungsten concentrate. The PFS contemplated an APT plant to convert tungsten concentrate into high purity APT. Metallurgical test work was completed as part of the PFS and is the basis for the MRE net smelter return (NSR) recovery assumptions of: W 70%, Cu 82.4%, Zn 76.2% and Pb 70.4%.

§ Infrastructure: O'Callaghans is strategically located just 10km south of Greatland's Telfer mine, with synergy potential from the sharing of Telfer's significant existing non-processing infrastructure.

Greatland Managing Director, Shaun Day, commented:

"O'Callaghans is a globally significant tungsten and base metals deposit that presents latent value and optionality within Greatland's portfolio, particularly in the strong prevailing tungsten market conditions.

"Greatland's first Mineral Resource Estimate for the deposit delineates a high grade 70 million tonne resource, the vast majority in the high confidence Indicated Resource category, providing a clearer basis to understand the scale and quality of this strategic asset.

"O'Callaghans is one of the world's largest high grade tungsten deposits, in close proximity to our Telfer mine which provides the potential to benefit from sharing of some of Telfer's non-processing infrastructure. While our primary focus will remain Telfer and Havieron, we are considering appropriate options to demonstrate and enhance the project's value within the Greatland portfolio."

Contact

For further information, please contact:

Greatland Resources Limited

Shaun Day, Managing Director  |  Andrew Bowler, Head of Investor Relations

info@greatland.com.au

Nominated Advisor

SPARK Advisory Partners

Andrew Emmott / James Keeshan / Neil Baldwin  |  +44 203 368 3550

Corporate Brokers

Canaccord Genuity  |  James Asensio / George Grainger  |  +44 207 523 8000

RBC Capital Markets  |  James Agnew / Jamil Miah  |  Scott Redwood  |  +44 207 029 0528

Media Relations

Australia - Fivemark Partners  |  Michael Vaughan  |  +61 422 602 720

About Greatland

Greatland is a gold and copper mining company listed on the Australian Securities Exchange and London Stock Exchange's AIM Market (ASX:GGP and AIM:GGP) and operates its business from Western Australia.

The Greatland portfolio includes the 100% owned Telfer mine, the adjacent 100% owned brownfield world-class Havieron gold-copper development project, and a significant exploration portfolio within the surrounding region. The combination of Telfer and Havieron provides for a substantial and long life gold-copper operation in the Paterson Province in the East Pilbara region of Western Australia.

2025 O'Callaghans Mineral Resource

O'Callaghans is located 10km south of Telfer on mining lease M45/203 (Figure 1), in the Paterson Province of the East Pilbara region in Western Australia, approximately 485 km by road south-east of Port Hedland.

Figure 1: Satellite image showing Telfer mine and infrastructure and O'Callaghans deposit location

The O'Callaghans MRE is detailed in Table 1 below.

Table 1: 2025 O'Callaghans Mineral Resource Statement

Notes:

Mineral Resources are reported as at 31 December 2025, grades are reported to two decimal places to reflect appropriate precision in the estimate, and this may cause apparent discrepancies in totals. Cutoffs for the O'Callaghans MRE are applied based on a NSR using metal prices of US$25.74 lb W (equivalent to ~US$450/MTU APT), US$4.54 lb Cu, US$1.27 lb Zn and US$0.93 lb Pb.

O'Callaghans is one of the largest high grade tungsten deposits globally. Figure 2 below illustrates the deposit's positioning relative to other tungsten resources outside of China, Russia and North Korea.

Importantly, O'Callaghans also benefits from significant grades of recoverable copper (0.30%), zinc (0.67%) and lead (0.28%) (not included in Figure 2 which shows tungsten only).

Figure 2: Benchmarking of O'Callaghans MRE against global (ex-China, Russia and North Korea) tungsten deposits

Notes: Based on publicly available resource information - may not be an exhaustive list. Refer to the Appendix for associated sources. Resources are reported in accordance with JORC (2012) or NI 43-101. See the Appendix section for comparison data sources.

Additional Information on the O'Callaghans Mineral Resource Estimate

O'Callaghans

The O'Callaghans deposit is 100% owned by Greatland Resource Ltd and located 10km south of Greatland's Telfer gold-copper mine (Figure 1), in the Paterson Province of the East Pilbara region in Western Australia, approximately 485 km by road south-east of Port Hedland. The O'Callaghans Mineral Resource is located within an approved mining lease, M45/203.

Geology

The O'Callaghans deposit lies at the contact between the Proterozoic Puntapunta Formation and the O'Callaghans granite. The Puntapunta Formation conformably underlies the Wilki Quartzite and overlies the Telfer Formation, and is described as an outer carbonate shelf deposit consisting of well-bedded, clastic dolomite and limestone, with lesser amounts of calcareous sandstone and siltstone. The O'Callaghans granite has been identified at around 350 m below surface with drilling having defined a zone of poly-metallic skarn mineralisation up to 60m thick above the granite limestone contact. The O'Callaghans suite is directly associated with complex skarn zones, including pyrite-pyrrotite-magnetite skarns with a strong magnetic expression.

Figure 3: Schematic geological section of O'Callaghans deposit

Mineralisation

Mineralisation containing potentially economic quantities of tungsten, copper, zinc and lead has been identified approximately 300m below surface as a sub-horizontal layer of poly-metallic skarn (altered limestone) mineralisation up to 60m thick on the contact between a large granitic intrusion and overlying limestones (Figure 3). Tungsten-bearing minerals include both scheelite and wolframite. Molybdenum and silver are present but are not currently considered economically significant.

Drilling Overview

Exploration during the 1980s-1990s at O'Callaghans targeted skarn mineralisation associated with a geophysically interpreted granitoid. Reverse circulation (RC) drilling conducted across the project area during the 1980s-1990s tested multiple anomalies; however, most holes were insufficiently deep to intersect the skarn system. In 1985, seven diamond drillholes were completed to test discrete magnetic anomalies. Six holes intersected polymetallic skarn mineralisation, confirming a zoned system located approximately 300 m below surface.

The majority of drilling that informs this MRE was carried out between 2008-2010, including 19 diamond holes in 2008 and 157 diamond holes in 2009-2010, infilling the main mineralised zone to approximately 100m spacing.

Sampling Practices

Most data informing the mineral resource is from 2008-2010 drilling. Sample preparation was undertaken at Telfer (2008) and in Perth laboratories (2009-2010). Sample intervals ranged from 0.2m-1.0m. RC samples were collected at 1m intervals and split using riffle or rotary splitters, producing 2-5kg primary samples, with bulk rejects retained for reference. Diamond drilling (DD) sampling followed strict protocols, using geological boundaries, with half-core samples collected.

Both RC and DD samples were crushed (to ~2 mm), split, and pulverised (~75 µm) prior to assay, using protocols appropriate for the mineralisation. Quality control included ~5% field duplicates for RC and coarse duplicates for DD. No second half-core assays were conducted to preserve material for metallurgical test work.

Geological Interpretation

The O'Callaghans deposit is a polymetallic skarn located at the contact between limestone of the Puntapunta Formation and an intrusive granite. The Main Skarn comprises calc-silicate rocks with >10% sulphides, typically surrounded by a halo containing <10% sulphides. Geological interpretation was completed for lithology, structure, oxidation, and Pb/Zn metal zonation, based on drilling data. Lithological domains were treated as hard boundaries, with domains defined from both logging and assay data.

Structure and oxidation domains were modelled but have minimal impact on the resource estimate. Final estimation domains align with the geological interpretation, except for the refined Pb and Zn zonation. The deposit is characterised as a flat, disc-shaped orebody.

Mineral Resource Estimation

Drillhole data were composited to 2m lengths, with top-cuts applied to Pb/Zn domains and Mo based on statistical analysis, while all geological and grade domains treated as hard boundaries. Grade estimation was completed using ordinary kriging for W, Cu, Zn and Pb and reported for Mineral Resources.  

The Mineral Resource is reported through the use of a A$92 net-smelter-return (NSR) using metal prices of US$25.74/lb W (equivalent to ~US$450/MTU APT), US$4.54/lb Cu, US$1.27/lb Zn, and US$0.93/lb Pb and cost estimates based on a combination of the 2014 PFS physicals, current unit rates at nearby Telfer Mine and escalation from the 2014 PFS where current values were not available.

The Mineral Resource has been classified as Indicated where adequate drilling density exists (100m × 100m spacing) to demonstrate both geological and grade continuity within the main mineralised horizon. Inferred Resources form a peripheral halo to the Indicated category, where drill spacing widens from 100m to 200m. In these areas, geological continuity is established, but confidence in grade continuity is lower due to increased spacing.

Mineral Resource classification is also constrained by a mine stope-optimised solid derived using a A$92 NSR cut-off. This approach ensures that the classification is limited to material within a realistic and potentially mineable stope geometry.

Mining and Metallurgical Assumptions

A Pre-Feasibility Study (PFS) was completed by previous owner Newcrest Mining Limited in 2014 that identified long-hole open stoping as the preferred mining method with decline truck haulage identified as the most suitable to deliver a 2.0Mtpa operation. The proposed processing route involves sequential flotation (copper, lead, zinc, and pyrite), followed by magnetic separation and gravity recovery of tungsten concentrate, through a new onsite processing facility. The PFS contemplated an APT plant to convert tungsten concentrate into high purity APT.

Metallurgical domains are based on the skarn geology, with subdivision into lead-zinc rich and lead-zinc poor zones. Metallurgical test work has been completed on representative samples from both domains with the following recovery assumptions used for NSR calculation: W 70%, Cu 82.4%, Zn 76.2% and Pb 70.4%.

Comparison to Previous Mineral Resources

The O'Callaghans Mineral Resources has previously been reported as a Mineral Resource by both Newcrest Mining Limited and then Newmont Corporation between 2010 and 2023. It was not included by Greatland in its December 2024 MRE as a technical evaluation was ongoing at that time. With this work now complete it is the view of the Competent Person that the underlying data and relevant estimation support Greatland reporting a Mineral Resource estimate for the O'Callaghan deposit.

Figure 4 provides a comparison between previous reported Mineral Resources for the O'Callaghans Deposit.

Figure 4: Comparison with previous Mineral Resource estimates

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Forward Looking Statements

This document includes forward looking statements and forward looking information within the meaning of securities laws of applicable jurisdictions. Forward looking statements can generally be identified by the use of words such as "may", "will", "expect", "intend", "plan", "estimate", "anticipate", "believe", "continue", "objectives", "targets", "outlook" and "guidance", or other similar words and may include, without limitation, statements regarding estimated reserves and resources, certain plans, strategies, aspirations and objectives of management, anticipated production, study or construction dates, expected costs, cash flow or production outputs and anticipated productive lives of projects and mines.

These forward looking statements involve known and unknown risks, uncertainties and other factors that may cause actual results, performance and achievements or industry results to differ materially from any future results, performance or achievements, or industry results, expressed or implied by these forward-looking statements. Relevant factors may include, but are not limited to, changes in commodity prices, foreign exchange fluctuations and general economic conditions, increased costs and demand for production inputs, the speculative nature of exploration and project development, including the risks of obtaining necessary licences and permits and diminishing quantities or grades of reserves, political and social risks, changes to the regulatory framework within which Greatland operates or may in the future operate, environmental conditions including extreme weather conditions, recruitment and retention of personnel, industrial relations issues and litigation.

Forward looking statements are based on assumptions as to the financial, market, regulatory and other relevant environments that will exist and affect Greatland's business and operations in the future. Greatland does not give any assurance that the assumptions will prove to be correct. There may be other factors that could cause actual results or events not to be as anticipated, and many events are beyond the reasonable control of Greatland. Forward looking statements in this document speak only at the date of issue. Greatland does not undertake any obligation to update or revise any of the forward looking statements or to advise of any change in assumptions on which any such statement is based.

Competent Person Statement

The information in this announcement pertaining to estimation and reporting of the Mineral Resource estimates is based on, and fairly reflects, information and supporting documentation compiled under the supervision of Michael Thomson, Principal Geologist at Greatland. Mr Thomson is a full-time employee of the Greatland Group and has a financial interest in the Company. Mr Thomson is a member of the Australian Institute of Geology (AIG) and has over 20 years' relevant industry experience. Mr Thomson has sufficient experience that is relevant to the style of mineralisation and type of deposits under consideration and to the activity currently being undertaken to qualify as a Competent Person as defined in the 2012 Edition of the 'Australasian Code for Reporting Exploration Results, Mineral Resources and Ore Reserves'. Mr Thomson consents to the inclusion in this announcement of the matters based on that information and supporting documentation in the form and context in which it appears.

Independent consulting group SRK Consulting (Australasia) Pty Ltd (SRK) has reviewed the O'Callaghans Mineral Resource and is of the opinion that the supporting geological dataset and the geological and estimation methodologies used to the produce the Mineral Resource Estimate are reasonable and appropriate for the style of mineralisation of the deposit. Further, SRK considers that the Mineral Resources have been classified and reported in accordance with the guidelines and principals outlined in the 2012 edition of the Australasian Code for the Reporting of Exploration Results, Mineral Resources and Ore Reserves (JORC Code, 2012 edition).

Appendix 1: JORC Tables

JORC Code, 2012 Edition - Table 1 Section 1: Sampling Techniques and Data

JORC Code, 2012 Edition - Table 1 Section 2: Reporting of Exploration Results

JORC Code, 2012 Edition - Table 1 Section 3: Estimation and Reporting of Mineral Resources

Appendix 2: Tungsten Mineral Resource Estimate Benchmarking