Drilling Commences at Target A1

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 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.