Mushima North - planned drill programme

Tertiary Minerals plc (AIM: TYM) is pleased to provide an update on planned activities, including a deeper drill programme, at Target A1, Mushima North Project (“Mushima North” or the “Project”), Zambia.

Target A1 is a polymetallic, silver-copper-zinc prospect, where the Company has previously

reported a near-surface Exploration Target range of 15-30 million tonnes at 40-60 g/t silver

equivalent (up to 58 million ounces silver equivalent) at the Discovery Zone.

Mushima North is located in the prospective Iron-Oxide-Copper-Gold region of Zambia and is

located 28km to the east of the historic Kalengwa copper-silver mine which is currently under

redevelopment.

Highlights:

 The drilling aims is to test for the continuation of mineralisation beneath the Discovery Zone, targeting higher-grade mineralisation and the potential for an underlying primary sulphide deposit.

 The last drill programme provided further support and increased confidence in the Exploration Target, extended mineralisation at depth and included the best drill intersections to date:

 121m at 56g/t Ag, 0.26% Cu and 0.37% Zn (78 g/t Ag equivalent) from 4m downhole (26TMNRC-053; drillhole ends in mineralisation).

 Including: 52m at 99g/t Ag, 0.41% Cu and 0.43% Zn (130 g/t Ag equivalent) from 39m downhole.

 And: 10m at 165g/t Ag, 1.01% Cu and 0.78% Zn (238 g/t Ag equivalent) from 80m downhole.

82m at 89 g/t Ag, 0.20% Cu and 0.38% Zn (107 g/t Ag equivalent) from 8m downhole (26TMNRC-066; drillhole ends in mineralisation).

Including: 37m at 165 g/t Ag, 0.28% Cu and 0.58% Zn (191 g/t Ag equivalent) from 53m downhole.

 Up to 1,000m diamond drill programme planned to start following the General Meeting of Shareholders to be held on 28 October 2026, subject to Shareholder approval of the recent £1,000,000 placing.

 Mineral Resource Estimate is expected before the end of the year.

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

“We are pleased to provide an update on the next steps for our flagship project in Zambia. This programme marks our first planned diamond drill programme on the Project and will test for the continuation of mineralisation below the Discovery Zone, and in particular for the potential of underlying primary sulphides.

“With the completion of the recent fundraise, and subject to shareholder support at the upcoming General Meeting, we will have sufficient funds to undertake this additional drill programme. Extending the depth of mineralisation and identifying an underlying sulphide system would have significant positive implications for the Project, and we are excited to get back into the field and continue drilling.

“Other additional planned programmes include expanding the analytical suite for critical metals including rare earth elements, additional metallurgical testwork, and environmental and community baseline surveys. With the last of the laboratory results for the recent drilling due soon, along with the initial metallurgical testwork results, we are gearing up for a very strong finish to this year’s Zambian field season. I look forward to providing further updates as these programmes advance.”

Drilling Programme

A programme of approximately 1,000m diamond drilling is planned as an initial “proof of concept” programme to test for the continuation of mineralisation at depth beyond the current mineralisation being defined by the recent Phase 4 programme. Currently, up to 4 holes, each between 200m and 250m in length, inclined at approximately (-60 to -70°) are planned. This will test for mineralisation up to a vertical depth of approximately 200m, considerably deeper than the current Exploration Target (~95m vertically) and the recent Phase 4 drill programme (maximum hole depth 125m vertically).

The new drill programme at Target A1 is designed to:

Test the depth extent of mineralisation below the Discovery zone and the potential for primary sulphide mineralisation.

Increase the geological (lithological and structural) understanding of the deposit to support orebody knowledge and future drilling and technical studies.

Provide drill core samples for additional metallurgical and technical testwork.

The drill programme is expected to commence as soon as the funding is secured following the General Meeting to be held on 28 October 2026, with access and field preparation expected to start in the coming days. The drill programme is estimated to take approximately 4 weeks to complete. Samples will be initially analysed on site using a portable X-Ray Fluorescence (“pXRF”) analyser for copper and zinc. Selected mineralised intervals will also be submitted for external assaying at a certified laboratory for a wider suite of elements than previously analysed for, including silver, copper, zinc, cobalt, bismuth, antimony, gallium, gallium and rare earth elements. These will be submitted in regular batches throughout the drill programme, with the first results expected approximately 6-8 weeks after the initial batch is submitted.

Figure 1. The northern part of the Target A1 copper-in-soil anomaly, including the plan view of the 3D mineralisation model of the Discovery Zone used to help derive the Exploration Target (500m long, 300m wide and 75m thick), and the location of the shallow, copper mineralisation recently intersected in the Western Zone. Completed holes from the recent Phase 4 programme (green) and earlier drill phases (yellow).

Target A1 silver oxide discovery

The Company has previously reported a JORC-compliant Exploration Target for the Discovery Zone of between 15 and 30 million tonnes with an average grade of between 40 and 60 g/t silver equivalent for up to 58 million ounces silver equivalent. As currently defined, this is a near-surface, tabular body located within the oxide zone and is some 500m long, 300m wide and up to 75m thick (based on a lower cut-off of 25 g/t silver equivalent). The mineralisation remains open to the northwest, southwest and at depth, so the full extent and true geometry of the mineralisation remain to be determined. Further information on the Exploration Target can be found in the Company’s announcement on 30 March 2026.

Recent Phase 4 drilling defined a higher-grade zone with a surface footprint of up to 400m by 150m, and mineralisation down to a vertical depth of 125m, the current maximum depth of drilling, and the mineralisation remains open at depth. The potential for the near-surface oxide mineralisation to transition to underlying sulphide mineralisation has yet to be tested. Elevated bismuth (up to 0.53%), antimony (up to 0.22%), cobalt (0.39%) and gallium (up to 40 g/t) are also associated with the mineralisation, but, as yet, have not been fully investigated.

A new shallow, copper mineralised zone located approximately 900m west-southwest from the Discovery Zone was also identified during the Phase 4 drilling. This zone, called the Western Zone, has also only been intersected in scout drilling and remains open.

Mushima North Project

Figure 2. Geological map of the Mushima North Project showing the locations of the priority targets within the licence area and their distance from Target A1 relative to 5km radius rings.