Great Western Mining Corporation PLC / AIM: GWMO / Euronext Growth: 8GW

28 May 2026

GREAT WESTERN MINING CORPORATION PLC

("Great Western", "GWM" or the "Company")

Option Agreement with Copper Producer over Eastside-Tango Project

Validates partnership strategy and provides exposure to long term royalty income

Great Western, a strategic minerals exploration and development company, is pleased to announce that it is party to an Option Agreement with KGHM Polska Miedz S.A. Group ("KGHM") in respect of the pooled Eastside-Tango copper porphyry project in Nevada (the "Project") in which the Company holds a 30% participating interest. Under the Option Agreement, KGHM may earn up to a 100% interest in the Project.

HIGHLIGHTS

·      Option Agreement signed with global copper producer KGHM

·      KGHM may earn a 100% interest through staged payments and a minimum exploration commitment of US$5 million during a six-year option period

·      An execution payment and annual option payments over the six-year option period will total US$650,000 (aggregate US$195,000 net to Great Western)

·      2% net smelter royalty retained by the Eastside-Tango Parties (0.6% net to Great Western)

·      Further advance royalty and milestone payments linked to declaration of a Resource, Preliminary Economic Analysis and Feasibility Study (aggregate US$675,000 net to Great Western)

·      Transaction supports Great Western's strategy of partnering assets while retaining long-term upside exposure

Great Western Chairman Brian Hall commented: "The Option Agreement with KGHM is a clear endorsement of the Eastside-Tango asset and of our project generation strategy, supporting disciplined capital allocation while preserving upside. Securing an agreement with a globally established copper producer validates the prospectivity of the wider district and highlights the potential value of the copper opportunity at our nearby Huntoon Copper Project. This transaction delivers immediate value, while retaining long-term royalty exposure and transferring future funding of the asset to a well-capitalised operator.

With tungsten recognised as a critical defence, industrial metal in short supply and tungsten prices now at record levels, management and financial resources are currently concentrated on advancing our tungsten opportunities on a 3 km corridor between the Defender Mine and our M2 copper resource.  This project is the focus of a major exploration campaign initially aimed at achieving a maiden Mineral Resource Estimate by the end of 2026.  We look forward to providing updates over the coming weeks as exploration efforts intensify."

DETAILS

Background

Great Western holds a broad portfolio of strategically located exploration assets across the Walker Lane belt of Nevada, providing optionality and potential value through further exploration success, partnerships or selective development.

On 2 August 2024, Great Western entered into a pooling agreement with Bronco Creek Exploration, a division of TSXV-listed Elemental Royalty Corporation, combining Great Western's Eastside Mine claims with Bronco Creek's adjoining Tango claims to form the Eastside-Tango Project. Under that agreement, Great Western and Bronco Creek hold participating interests of 30% and 70% respectively (together, the "Eastside-Tango Parties").

Terms of the Option Agreement

KGHM may earn a 100% interest in the Eastside-Tango Project over an option period of up to six years.

Upon option exercise by KGHM, Great Western will retain a net smelter royalty on the project of 0.6%.

Prior to exercising its option, KGHM will make an execution payment of $50,000 ($15,000 net to GWM) and annual advance royalty ("AAR") payments of $50,000 ($15,000 net to GWM), which will increase by $10,000 per year ($3,000 net to GWM), until a total of $1,750,000 has been paid or until commercial production commences.   There will fewer AARs if the option is exercised before the end of the six-year period,

Following exercise of the option, milestone payments will also be payable to the Eastside-Tango Parties as the Project advances:

·      US$500,000 on declaration of a resource (US$150,000 net to Great Western)

·      US$750,000 on completion of a Preliminary Economic Assessment (US$225,000 net)

·      US$1,000,000 on completion of a Feasibility Study (US$300,000 net)

Overview of the Tango-Eastside Project

The Eastside-Tango Project represents a pooled land package between GWM's Eastside Mine Claims and Elemental's adjoining Tango claims, targeting a porphyry copper-molybdenum system located approximately 18 km southeast of GWM's Huntoon Copper Project. Locally abundant quartz-copper oxide veining and associated widespread sericite pyrite alteration outcrops over an approximately 2-by-2-km area. The outcropping system footprint is bounded by post-mineral volcanic and alluvial cover to north and east. Historical drilling by Conoco and Humble Oil in the 1960s and 70s failed to test the system sufficiently, largely due to shallow hole depths and a poor understanding of the alteration vectors. An IP survey completed by Great Western in 2021 detected chargeability anomalies highlighting priority targets within untested zones of the system. The host rock stratigraphy includes Ordovician carbonate units representing additional potential for skarn/replacement mineralisation as well as the primary porphyry copper target.

Forward Looking Statements

This announcement contains forward looking statements relating to the plans, activities and expectations of Great Western Mining Corporation PLC. Such statements include, but are not limited to, those concerning planned exploration programmes, anticipated timelines and potential mineral resource outcomes. Forward looking statements are typically identified by words such as "plan", "expect", "anticipate", "intend", "may", "could", "potential" or similar expressions.

These statements are based on current expectations and assumptions and involve risks and uncertainties that could cause actual results to differ materially. Factors include geological risk, exploration and drilling results, permitting and regulatory approvals, funding availability, operational challenges, commodity price movements and general market conditions. No assurance can be given that any forward looking statements will prove to be accurate, and shareholders are cautioned not to place undue reliance on them.

ENDS

For further information visit www.greatwesternmining.com or contact:

Notes

Great Western Mining Corporation PLC (AIM: GWMO / Euronext Growth: 8GW) is an exploration and development company focused on strategic minerals across several 100%-owned claim groups in Mineral County, Nevada, a highly prospective and mining-friendly jurisdiction. The Company has an increasing strategic emphasis on tungsten as a critical mineral, while continuing to advance its Huntoon Copper Project, which hosts a JORC-compliant resource of 4.3 Mt at 0.45% Cu with further porphyry upside. It also maintains exposure to gold and silver through exploration and tailings reprocessing opportunities, alongside evaluating farm-out and joint venture options to unlock wider portfolio value.