("Tertiary" or the "Company")

27 July 2026

Non-Executive Director Change

Tertiary Minerals plc (AIM: TYM) is pleased to announce the appointment of Mr. Lorenz Werndle as an independent non-executive director ("NED") of the Company with immediate effect. Mr. Werndle will replace Mr. Donald McAlister on the Board, who is stepping down from his role on the 4 August 2026 due to other full time work commitments.

Mr. McAlister has served on the Board for over 25 years, ever since the Company first became admitted to trading on the AIM Market.

Mr. Werndle is a finance executive with experience across mining, strategy, corporate development and mergers and acquisitions, both internationally and in southern Africa. He is currently the Chief Financial Officer and Executive Director for Kavango Resources plc, an LSE-listed exploration and development company with projects in Botswana and Zimbabwe. Prior to this he served as CFO of Blue Gold Limited, a Nasdaq-listed company, and has also had leadership roles with Mwana Africa Plc, Lonrho Plc and Ambrian Plc.

Mr. Werndle will replace Mr. McAlister as Chairman of the Audit and Risk Committee and will sit on the Nomination and Remuneration Committees. He will be put forward for election at the AGM to be held in 2027, in accordance with the Company's Articles.

Patrick Cheetham, Chairman of Tertiary Minerals plc, commented:

"Donald will be very much missed for his huge industry experience and his sound advice. He has been a great sounding board for me, personally, since we listed the Company on AIM. We have been fortunate to secure Lorenz as his replacement. Lorenz brings many of the same skills and experience to the Board, and his African experience will be invaluable as we continue the exploration of our exciting Zambian exploration projects."

Lorenz Werndle, newly appointed Non-Executive Director, commented:

"I'm delighted to be joining the Tertiary Minerals Board. The Company has an exciting portfolio in Zambia and Nevada with real potential, and I'm looking forward to working with Patrick and the rest of the Board to support the team as they unlock this potential. I'd also like to acknowledge Donald for his long service to the Company and wish him well."

The following information is disclosed pursuant to Rule 17 and Schedule Two paragraph (g) of the AIM Rules for Companies in relation to Mr. Lorenz Joseph Werndle, aged 51:

Mr. Werndle holds no shares in the Company and holds no warrants or options over the Company's shares.

There are no further disclosures required under Schedule 2(g) of the AIM Rules for Companies.

Further Information:

Market Abuse Regulation

The information contained within this announcement is deemed by the Company to constitute inside information as stipulated under the Market Abuse Regulation (EU) No. 596/2014 as it forms part of UK domestic law by virtue of the European Union (Withdrawal) Act 2018 ('MAR'). Upon the publication of this announcement via Regulatory Information Service ('RIS'), this inside information is now considered to be in the public domain.

About Tertiary Minerals plc

Tertiary Minerals plc (AIM: TYM) is an AIM-traded mineral exploration and development company whose strategic focus is on energy transition metals. The Company's projects are all located in stable and democratic, geologically prospective, mining-friendly jurisdictions. Tertiary's current principal activities are the discovery and development of copper and precious metal mineral resources in Nevada and in Zambia.