New pXRF Drill Results from Target A1

("Tertiary" or the "Company")

24 August 2026

New pXRF Drill Results from Target A1, Mushima North

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.

Mushima North is located in the prospective Iron-Oxide-Copper-Gold region of Zambia. Target A1 is a polymetallic, silver-copper-zinc prospect located 28km to the east of the historic Kalengwa copper-silver mine which is currently under redevelopment.

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.

•   Reported values were produced using a pXRF analyser to test unprepared samples and as such are of a preliminary nature but provide an indication of potential mineralisation.

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.

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

Sampling, Analysis and QAQC

Sampling from the drilling programme was undertaken at 1m intervals and two subsamples were collected from each interval using a riffle splitter: one for potential laboratory analysis, the other for future reference.

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.

Samples from selected drill holes based on the initial pXRF results are being sent to the independent laboratory, ALS Global, located in South Africa for analysis for a range of elements using a four-acid digest, method code ME-ICP61 (including silver, copper, zinc, bismuth, antimony and gallium). QA samples (Certified Reference Material, duplicates, blanks) will be inserted and monitored as part of the Quality Assurance Quality Control ("QAQC") protocol.

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

The Mushima North Copper Project (Licence 27068-HQ-LEL) is held through Group company Copernicus Minerals Limited ("Copernicus"), which is 90% owned by Tertiary Minerals (Zambia) Limited and 10% by local partner, Mwashia Resources Limited.

The Project is under a technical cooperation agreement with First Quantum Minerals Limited ("FQM"), which allows Tertiary to benefit from FQM's historic exploration data in the area, as well as FQM's geological team's extensive experience and understanding of the area's geology. The agreement is non-binding and does not create any obligation to enter into any further agreement.  There are no commercial restrictions for Tertiary and FQM does not have a right of first refusal over the Project. Further details can be found in the announcement on 15 September 2022.

Target A1 lies 28km to the east of the Kalengwa Copper (-Silver) Mine in northwest Zambia, one of the highest-grade copper deposits ever to be mined in Zambia. In the 1970s, high-grade ore, averaging approximately 11% Cu copper, was trucked for direct smelting at other mines in the Copperbelt. The Kalengwa Mine is currently under redevelopment.

Numerous other geochemical and/or geophysical targets (B1, B2, B3, C2) are yet to be drill tested, the majority of which are located within a 12km radius of Target A1.

Further Information:

Market Abuse Regulation

The information contained within this announcement is deemed by the Company to constitute inside information as stipulated under the Market Abuse Regulation (EU) No. 596/2014 as it forms part of UK domestic law by virtue of the European Union (Withdrawal) Act 2018 ('MAR'). Upon the publication of this announcement via Regulatory Information Service ('RIS'), this inside information is now considered to be in the public domain.

Cautionary Note Regarding Forward-Looking Statements

The news release may contain certain statements and expressions of belief, expectation or opinion which are forward looking statements, and which relate, inter alia, to the Company's proposed strategy, plans and objectives or to the expectations or intentions of the Company's directors. Such forward-looking statements involve known and unknown risks, uncertainties, and other important factors beyond the control of the Company that could cause the actual performance or achievements of the Company to be materially different from such forward-looking statements. Accordingly, you should not rely on any forward-looking statements and, save as required by the AIM Rules for Companies or by law, the Company does not accept any obligation to disseminate any updates or revisions to such forward-looking statements.

Competent Persons Statement

The technical information in this release has been compiled and reviewed by Dr. Richard Belcher (CGeol, EurGeol) who is a qualified person for the purposes of the AIM Note for Mining and Oil & Gas Companies. Dr. Belcher is a chartered fellow of the Geological Society of London and holds the European Geologist title with the European Federation of Geologists.

About Tertiary Minerals plc

Tertiary Minerals plc (AIM: TYM) is an AIM-traded mineral exploration and development company whose strategic focus is on energy transition metals. The Company's projects are all located in stable and democratic, geologically prospective, mining-friendly jurisdictions. Tertiary's current principal activities are the discovery and development of copper and precious metal mineral resources in Nevada and in Zambia.