New pXRF Drill Results from Target A1

Tertiary Minerals plc (AIM: TYM) is pleased to announce the last remaining portable X-Ray Fluorescence ("pXRF") results of drill samples from the Phase 4 drill programme at Target A1, Mushima North Project in Zambia ("Mushima North" or the "Project). The remaining results continue to support the previously reported near surface Exploration Target of 15-30 million tonnes at 40-60 g/t silver and the presence of an area of higher-grade mineralisation both of which are part of what has been termed the Discovery Zone.

Highlights:

Ø Further confirmation of a zone of higher-grade silver-copper mineralisation supported by drill intersections including (downhole widths, true widths unknown):

• 7m at 0.52% Cu from 48m downhole (26TMNRC-080).
• 5m at 0.57% Cu from 66m downhole (26TMNRC-078).

Ø More evidence to support the continuity of the wider Exploration Target of near surface silver-copper-zinc oxide mineralisation, with drill intersections including (downhole widths, true widths unknown):

• 66m at 0.30% Cu from 14m downhole (26TMNRC-078).
• 68m at 0.28% Cu from 13m downhole (26TMNRC-080).

Ø While the Company is currently reporting only copper and zinc pXRF results in full, as pXRF is less reliable for silver, both the high-grade zone and the larger exploration target have yielded further values of up to 115 and 144 g/t silver respectively in line with expectations.

Ø All selected drill samples have now been submitted to the certified laboratory and results are expected over the coming weeks.

Ø Initial metallurgical testwork to commence imminently, followed by the Mineral Resource modelling.

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

"These final pXRF results from the recent Phase 4 drill programme continue to support our current exploration model and the overall extent of the mineralisation as well as the presence of the higher-grade silver and copper mineralisation previously reported at the Discovery Zone.

"With the recent discovery of additional copper mineralisation at the Western Zone some 900m west of the Discovery Zone, then there is potential to expand the mineralisation footprint in the immediately surrounding area outside of our current Exploration Target at the Discovery Zone. We also have other high-priority targets in the wider area that are yet to be drill tested.

"We now eagerly await the certified laboratory results at this very exciting time for the Company as we continue to advance this recent discovery towards our stated goal for this year which is to report a maiden Mineral Resource Estimate".

Drill Results

The latest preliminary results from the Company's internal analysis using a pXRF analyser continue to support the extent and continuity of the Oxide Exploration Target and the presence of a higher-grade silver and copper zone within the core of this.

The potential extent and tenor of silver mineralisation is not yet being reported as the pXRF results for silver are not regarded as being sufficiently reliable to support doing this. Certified, independent laboratory analysis, however, is currently underway to confirm silver values, along with copper and zinc and other potential, important accessory metals including bismuth, antimony and gallium.

pXRF results from all 39 drill holes from Phase 4 drill programme have now been released and mineralised intervals from selected holes have now been submitted to the certified laboratory for analysis. The certified laboratory results will be announced on an on-going basis as they become available.

Table 1. New pXRF intersections for copper and zinc from the Phase 4 drill programme, Target A1 and Target A2.

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) or zinc (intervals start and end with ≥0.2% Zn, and the average grade cut-off is 0.2% Zn) and allow for up to 3m internal consecutive dilution.

Figure 1. Cross-section (location on Figure 2) showing pXRF copper results only for new drill holes 26TMNRC-077 and 26TMNRC-078 and previously reported holes 26TMNRC-056 to 26TMNRC-059 and 26TMNRC-065, overlaid on the current Exploration Target mineralisation (silver-copper-zinc) boundary (to be updated as part of the Mineral Resource Estimation work).

Figure 2. 3D mineralisation model of the Discovery Zone 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. Completed holes from this programme (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 and a qualitative assessment of the silver 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