Drilling Commences at Target A1

05 November 2025

Tertiary Minerals plc

 ("Tertiary" or the "Company")

 Drilling Commences at Target A1, Mushima North Project, Zambia

Tertiary Minerals plc (AIM: TYM) is pleased to announce commencement of drilling at Target A1, a polymetallic (silver-copper-zinc) prospect and part of the Mushima North Project ("Mushima North" or the "Project), Zambia.

Mushima North is located in the prospective Iron-Oxide-Copper-Gold region of Zambia. Target A1 is located 28km to the east of the historic Kalengwa copper-silver mine which is currently under redevelopment.

Highlights:

Ø Planned drilling programme of approximately 1,000m of Reverse Circulation drilling.

Ø Drilling to test:

o  further lateral extensions of the known mineralisation, particularly around the high-grade silver and copper mineralisation in the north.

o  the continuity of mineralisation between wider-spaced drill lines, by obtaining additional mineralisation intersections.

o  the depth extension of the known mineralisation.

Ø Phase 2 drilling of this target in mid-2025 returned drill intersections including (downhole widths, true widths unknown):

o  58m at 49 g/t Ag, 0.26% Cu and 0.16% Zn (72 g/t Ag equivalent or 0.94% copper equivalent) from 8m downhole (hole 25TMNAC-038).

§ Including: 20m at 86 g/t Ag, 0.44% Cu and 0.24% Zn from 46m downhole.

§ And: 9m at 124 g/t Ag, 0.73% Cu and 0.25% Zn (185 g/t Ag equivalent or 2.40% copper equivalent) from 57m downhole. The hole ended in mineralisation.

o  73m at 32 g/t Ag, 0.16% Cu and 0.24% Zn (49 g/t Ag equivalent or 0.64% copper equivalent) from 11m downhole (hole 25TMNAC-025).

§ Including: 21m at 66 g/t Ag, 0.21% Cu and 0.30% Zn from 50m downhole.

Ø Drilling is expected to be completed within two weeks.

Richard Belcher, Managing Director of Tertiary Minerals plc, commented:

"We are excited to be drilling again this year at Target A1, which currently has a surface footprint of approximately 450m by 400m, with mineralisation intersected to a vertical depth of up to 84m.

"The aim of this drill programme is to follow-up on the highly encouraging drilling results from previous drill phases, testing the potential continuation of mineralisation along strike and at depth, as well as providing additional infill drilling. This work is aimed at bringing us closer to our goals of producing, in the short-term, an Exploration Target, as well as a maiden mineral resource in the next 12 months.

"I look forward to updating shareholders on the drilling progress and results in the coming weeks."

Drilling Programme

A programme of approximately 1,000m of Reverse Circulation ("RC") drilling is planned along a series of east-west drill lines spaced approximately 100m apart (north-south). Holes will be collared approximately 50 to 100m apart along the east-west lines and drilled to a nominal depth of approximately 100m. Deeper holes (approximately 150m) will also be undertaken in key areas to further understand the potential continuation of mineralisation at depth. The drill programme at Target A1 is designed to test:

· further lateral extensions of the known mineralisation, particularly around the high-grade silver and copper mineralisation previously intersected in drillhole 25TMNAC-038.

· the continuity of mineralisation between wider-spaced drill lines, by obtaining additional mineralisation intersections.

· the depth extension of the known mineralisation up to 150m vertically.

In addition, initial mineralogical work is already underway to provide insights into the type and styles of mineralisation. The Company is also planning to prepare an Exploration Target which, following the guidelines of the JORC Code, will comprise an estimate of the exploration potential of Target A1 in the form of a range of tonnes and grades based on the work completed at the time of reporting.

This is part of the Company's over-arching goal of producing a maiden mineral resource for Target A1 in the next 12 months.

The drill programme is being conducted by Ox Drilling which also completed the Phase 1 and Phase 2 drill programmes. The drill programme is expected to take approximately 2 weeks to complete and is planned to be finished prior to the on-set of the heavy rains in the area which will likely prevent further on-the-ground exploration until March-April 2026. Samples will be initially analysed on site using a portable X-Ray Fluorescence ("pXRF") analyser for copper and zinc to support the programme and provide initial results on each hole. Selected mineralised intervals will then be submitted for external analysis at a certified laboratory for a suite of elements, including silver, copper, zinc, bismuth, antimony and gallium. Expected laboratory turn-around times for analysis is currently around 4-6 weeks from submission.

For further information about the Drilling Programme and Target A1 see the news release of 31 October 2025.

Mushima North Project

The Mushima North Copper Project (Licence 27068-HQ-LEL) is held through Group company Copernicus Minerals Limited ("Copernicus"), which is 90% owned by Tertiary Minerals (Zambia) Limited and 10% by local partner, Mwashia Resources Limited.

The Project lies 20km to the east of the Kalengwa copper mine in northwest Zambia, one of the highest-grade copper deposits ever to be mined in the country. In the 1970s, high-grade ore, average approximately 11% Cu copper, was trucked for direct smelting at other mines in the Copperbelt. The Kalengwa mine is currently under redevelopment and is expected to produce 15,000 tonnes of copper annually.

Numerous other geochemical and/or geophysical targets (A2, B1, B2, B3, C2) are yet to be drill tested. Many of these are located within 12km of Target A1.

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.

Cautionary Note Regarding Forward-Looking Statements

The news release may contain certain statements and expressions of belief, expectation or opinion which are forward looking statements, and which relate, inter alia, to the Company's proposed strategy, plans and objectives or to the expectations or intentions of the Company's directors. Such forward-looking statements involve known and unknown risks, uncertainties, and other important factors beyond the control of the Company that could cause the actual performance or achievements of the Company to be materially different from such forward-looking statements. Accordingly, you should not rely on any forward-looking statements and, save as required by the AIM Rules for Companies or by law, the Company does not accept any obligation to disseminate any updates or revisions to such forward-looking statements.

Competent Persons Statement

The technical information in this release has been compiled and reviewed by Dr. Richard Belcher (CGeol, EurGeol) who is a qualified person for the purposes of the AIM Note for Mining and Oil & Gas Companies. Dr. Belcher is a chartered fellow of the Geological Society of London and holds the European Geologist title with the European Federation of Geologists.

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 Zambia and Nevada, USA.

Figure 1. Geological map of the Mushima North Project showing the locations of the priority targets within the licence.

Figure 2. Location map of Target A1 showing soil sample results for copper and zinc, and the collar locations for the previous and upcoming planned drilling programme.