New Shallow Copper Mineralised Zone Discovered

Tertiary Minerals plc (AIM: TYM) is pleased to announce the preliminary results from portable X-Ray Fluorescence ("pXRF") analysis of samples from two scout holes drilled to the west of the Discovery Zone at Target A1, Mushima North Project in Zambia ("Mushima North" or the "Project") as part of the recently completed drill programme.

The pXRF results indicate the presence of a shallow zone of copper mineralisation approximately 900m west-southwest of the Discovery Zone (Exploration Target of 15-30 million tonnes at 40-60 g/t silver equivalent) in an area the Company is now calling the Western Zone.

Highlights:

Ø The Western Zone is a newly discovered mineralised copper zone approximately 900m west-southwest of the Discovery Zone within Target A1.

Ø Drill intersections include (downhole widths, true widths unknown):

o 25m at 0.38% Cu from 19m downhole (26TMNRC-076).

• Including: 13m at 0.53% Cu from 29m downhole.
• And: 3m at 0.75% Cu from 33m downhole.

Ø Drilling at the Western Zone was carried out alongside a larger infill drilling programme at the Discovery Zone, Target A1.

Ø Additional pXRF results from the Discovery Zone and a scout hole at Target A2 are expected imminently.

Ø Certified laboratory results from the drill programme are expected over the coming weeks.

Ø Initial metallurgical testwork is set to commence imminently, followed by the Mineral Resource modelling at the Discovery Zone.

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

"We are excited to announce the pXRF results from the two scout drill holes drilled at the Western Zone, Target A1, which have intersected shallow copper mineralisation, including 13m at 0.53% Cu from only 29m below the surface. These holes are 900m to the west-southwest of the Discovery Zone and indicate the potential for additional mineralisation in a new zone well beyond the Exploration Target boundary at the Discovery Zone where we have recently completed infill drilling aimed at supporting the production of a Maiden Mineral Resource Estimate.

"These results continue to support our wider geological model and belief that the Mushima North Project has the potential to host a much larger mineralised system than has been delineated to date.

"While the current drill programme is now complete, we expect substantial newsflow over the coming weeks. This will include the remaining pXRF results for copper and zinc from the last seven holes drilled, as well as the certified laboratory results from across the entire drill programme inclusive of silver analyses for which our expectations in the Discovery Zone are justifiably high.

"I look forward to updating shareholders on these results as we advance the Mushima North Project with the aim of producing a Mineral Resource Estimate before the end of this year."

Drill Results

The two drill holes at the Western Zone, Target A1 (26TMNRC-075 and 26TMNRC-076) were drilled approximately 225m north of a line of 5 shallow, exploratory Air Core holes drilled in Phase 1. These holes targeted the western part of the Target A1 copper-in-soil anomaly and intersected low-grade copper mineralisation. The new holes were positioned based on our current understanding of the mineralisation within the Exploration Target at the Discovery Zone and its surface expression within the regolith. The pXRF results suggest the mineralisation at the Western Zone is copper only, rather than silver-copper-zinc as intersected at the Discovery Zone but this has yet to be confirmed by certified laboratory analysis.

pXRF results from the remaining 7 holes drilled are imminent and include the last of the infill drilling of the current Exploration Target at the Discovery Zone as well as the first scout drill hole drilled at Target A2. The certified laboratory results will be announced on an on-going basis as they become available.

Table 1. pXRF intersections for copper from the Phase 4 drill programme, Western Zone, Target A1.

Note to Table:

• Calculated intersections (downhole, true width unknown) are weighted averages based on copper (intervals start and end with ≥0.1% Cu, and the average grade cut-off is 0.1% Cu) and allow for up to 3m internal consecutive dilution.

Figure 1. Location of the two drill holes at the Western Zone, Target A1, in relation to the Discovery Zone showing the mineralisation model of Target A1 used to help derive the Exploration Target (500m long, 300m wide and 75m thick) located at the northern end of the copper-in-soil anomaly at Target A1. Phase 4 drill collars (this programme) are in green and earlier drill phases (yellow).

Drill Programme

A total of 39 holes (for 3,639m) Reverse Circulation ("RC") drill holes were drilled as part of the Phase 4 drill programme. For the drilling at the Discovery Zone, holes were collared along a series of east-west drill lines spaced approximately 100m apart (north-south) and 50m apart along the east-west lines and drilled to vertical depths of up to 128m. This was the maximum depth capability of the drill rig under the drilling conditions, in particular the higher-than-expected water table and resultant wet samples. Drilling was completed in two passes to allow the updating of the Company's geological model as new data became available and to enable the programme to be more dynamic.

Sampling, Analysis and QAQC

Samples are being initially analysed on site using a pXRF analyser for copper, zinc and silver. Analysis protocol includes the averaging of two analyses per sample (unprepared sample analysed through a thin plastic sample bag) and the inclusion of Certified Reference Material, blanks and duplicate samples as part of an internal Quality Assurance ("QA") procedure. Given the nature of the unprepared sample and point analysis, this method is being used as a preliminary analytical technique to provide an approximate quantitative measure of copper and zinc grades.

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

Target A1 Silver Oxide Discovery

The Company has previously reported a JORC-compliant Exploration Target for the Discovery Zone of between 15 and 30Mt with an average grade of between 40 and 60 g/t 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 and 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.

Elevated bismuth (up to 991 g/t), antimony (up to 824 g/t) 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 or the potential of additional mineralisation nearby, such as at the Western Zone, Target A1.

Mushima North Project