Mushima North Phase 4 lab results

Best silver-copper intersection to date at the Discovery Zone, Mushima North: 121m at 78 g/t silver equivalent from 4m depth and ending in mineralisation

Tertiary Minerals plc (AIM: TYM) is pleased to announce additional laboratory analytical results from the recent Phase 4 drill programme at the Discovery Zone in Target A1, Mushima North Project in Zambia (“Mushima North” or the “Project). The results follow the Company’s news releases regarding the laboratory analytical results on 1 and 7 September 2026 and are from a further thirteen drill holes.

All thirteen holes intersected near surface, silver-copper-zinc mineralisation, with several holes ending in mineralisation and thus extending the mineralisation at depth, including the best silver-copper intersection to date on the Project.

Mushima North is located in the prospective Iron-Oxide-Copper-Gold region of Zambia. Target A1 is a polymetallic, silver-copper-zinc prospect, where the Company has previously reported a near surface Exploration Target of 15-30 million tonnes at 40-60 g/t silver equivalent, and which is located 28km to the east of the historic Kalengwa copper-silver mine which is currently under redevelopment.

Highlights:

 Best silver-copper intersection to date at the Discovery Zone:

 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.

 Depth extent of mineralisation increased with multiple drill holes ending in mineralisation.

 Drill results provide further support and increased confidence in the Exploration Target of near surface silver-copper-zinc oxide mineralisation, with drill intersections including (downhole widths, true widths unknown):

 51m at 67g/t Ag, 0.16% Cu and 0.38% Zn (83 g/t Ag equivalent) from 28m downhole (26TMNRC-065; drillhole ends in mineralisation).

 Including: 28m at 102g/t Ag, 0.20% Cu and 0.28% Zn (118 g/t Ag equivalent) from 50m downhole.

 60m at 32 g/t Ag, 0.08% Cu and 0.41% Zn (44 g/t Ag equivalent) from 39m downhole (26TMNRC-068).

 Results include highest silver assay to date of 471 g/t from certified laboratory analytical results on the Project.

 Additional laboratory analytical results expected imminently.

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

“We are thrilled to report our best silver-copper mineralised intersection to date on the Project, returning 121m at 78 g/t silver equivalent, a further 24m longer than the previous Project record at 97m at 85 g/t silver equivalent. Even more impressive is that this new intersection starts from only 4m below the surface, with the hole ending in mineralisation at a vertical depth of 125m.

“This intersection along with the other drill holes results released today continue to deliver not only higher-grade silver intersections, with individual assays of up to 471 g/t silver, but also several impressive multi-metre copper intersections averaging over 1% copper, notably 10m at 1.01% copper from 80m downhole.

“We believe these results continue to support our bulk tonnage, open pit silver exploration model and the potential significance of this Project for the Company. Additional laboratory results are expected soon and we look forward to updating our shareholders in due course”.

Drill Programme and Results

Further information on the drill programme can be found in Company’s announcement on 8 June 2026.

The results in this announcement are for thirteen holes only (Figures 1, 2 and 3). Including these thirteen holes, results for a total of 25 holes have now been released from across the Exploration Target and include infill holes to increase confidence in the continuity of the mineralisation to the level required to report a Mineral Resource Estimate, testing of the Exploration Target mineralisation margin to potentially expand the footprint, and also targeting of the higher-grade mineralisation zone.

Accessory minerals such as bismuth, antimony and cobalt are also intersected in these holes as well as being present in previous drilling. While the potential for these metals has yet to be evaluated, they are classified as critical, and in some case strategic raw materials, (e.g. by the European Commission) and if economically feasible to extract along with the main silver-copper mineralisation, could have positive impacts of future economics.

Table 1. Additional analytical results (thirteen holes only, other analytical results from the remainder of the Phase 4 drill programme awaited). Equivalent grades (“Eq”) are for illustrative purposes only.

Note to Table:

Calculated intersections (downhole, true widths unknown) are weighted averages based on silver or copper (denoted in table by metal in bold). Using a cut-off grade of 10 g/t Ag or 0.1% Cu, respectively. Intervals start and end with ≥10 g/t Ag or 0.1% Cu, respectively and with up to 3m consecutive internal dilution allowed.

Silver values rounded to whole numbers.

EOH means End of Hole.

CuEq (%) and AgEq (g/t) are the copper and silver equivalent grades, respectively, and were calculated assuming commodity prices of Cu: US$4.99 lb, Ag: US$57 oz, Zn: US$1.38 lb and 100% recovery as used in reporting of previous results from Phase 2 and 3 drill programmes. No information on beneficiation recoveries is available at this stage. These are for illustrative purposes only.

Gram metres for silver are the silver values (g/t) multiplied by the intervals (m).

Figure 1. Cross-section (location on Figure 3) showing analytical results for silver for new drill holes 26TMNRC-052, 26TMNRC-053 and 26TMNRC-074 overlaid on the current Exploration Target mineralisation (silver-copper-zinc) boundary (to be updated as part of the Mineral Resource Estimation work).

Figure 2. Cross-section (location on Figure 3) showing analytical results for silver for new drill hole 26TMNRC-065 (along with previously reported drill holes) overlaid on the current Exploration Target mineralisation (silver-copper-zinc) boundary (to be updated as part of the Mineral Resource Estimation work).

Sampling, Analysis and QAQC

Reported drill hole intersection thicknesses are downhole thicknesses and true thicknesses are unknown. Intersections are weighted averages on silver (using a cut-off grade of 10 g/t Ag), copper (using a cut-off grade of 0.1% Cu) and zinc (using a cut-off grade of 0.2% Zn) with up to 3m internal dilution.

Target A1 Silver Oxide Discovery

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. The potential for the near surface oxide mineralisation to transition to underlying sulphide mineralisation has yet to be tested. Nor has the potential for expanding the mineralisation based on nearby targets, such as at the Western Zone, Target A1.

Mushima North Project