New Analytical Results for Mushima North

New analytical results from Phase 4 infill drilling at the Discovery Zone increases the depth extent of thick, near surface silver-copper mineralisation at Target A1, Mushima North

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 release of the first laboratory assay results on 1 September 2026 and are from a further seven drill holes.

All seven holes intersected near surface, silver-copper-zinc mineralisation and extend the mineralisation at depth with the majority of holes ending in mineralisation.

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:

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

Ø Infill drilling provides further support and increases confidence in the Exploration Target of near surface silver-copper-zinc oxide mineralisation, with drill intersections including (downhole widths, true widths unknown):

• 67m at 40g/t Ag, 0.10% Cu and 0.30% Zn (51 g/t Ag equivalent) from 19m downhole (26TMNRC-054; drillhole ends in mineralisation).
• 82m at 37 g/t Ag, 0.11% Cu and 0.54% Zn (53 g/t Ag equivalent) from 7m downhole (26TMNRC-057).
• 46m at 41 g/t Ag, 0.19% Cu and 0.65% Zn (63 g/t Ag equivalent) from 8m downhole (26TMNRC-058; drillhole ends in mineralisation).

Ø Higher-grade silver-copper mineralisation zone further supported, with drill intersections including (downhole widths, true widths unknown):

• 22m at 90 g/t Ag, 0.13% Cu and 0.44% Zn (105 g/t Ag equivalent) from 64m downhole (26TMNRC-054; drillhole ends in mineralisation).
• 12m at 80 g/t Ag, 0.21% Cu and 0.67% Zn (104 g/t Ag equivalent) from 35m downhole (26TMNRC-058; drillhole ends in mineralisation).
• 11m at 97 g/t Ag, 0.07% Cu and 0.54% Zn (110 g/t Ag equivalent) from 43m downhole (26TMNRC-058, drillhole ends in mineralisation).

Ø Additional laboratory analytical results expected over the coming weeks.

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

"Results from our infill drilling continue to increase our confidence on the extent and continuation of grade within the Exploration Target at the Discovery Zone, with intersections including 82m at 53 g/t silver equivalent (0.88% copper equivalent) from only 7m below surface. The higher-grade zone is further supported with the new results and includes an intersection of 22m at 105 g/t silver equivalent (1.75% copper equivalent) from 64m.

"Moreover, the majority of the holes reported here end in grade indicating the mineralisation remains open with depth and pushes the known depth of mineralisation beyond the envelope of the previously defined Exploration Target. The full depth extent and the possibility for the current oxide mineralisation to transition to sulphide mineralisation are yet to be tested.

"Additional laboratory results are expected over the coming weeks 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 seven holes only (including these seven holes, results for a total of 12 holes have now been released; Figures 1 and 2), and are from the northern section of 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 (seven 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 0.15 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 2) showing analytical results for silver for new drill holes 26TMNRC-056 to 26TMNRC-059 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 2) showing analytical results for silver for new drill holes 26TMNRC-054 to 26TMNRC-055 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 0.13%), 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