Announcement • Sep 07

Tertiary Minerals Announces New Analytical Results from Phase 4 Infill Drilling At Discovery Zone Increases Depth Extent of Silver-Copper Mineralisation At Target A1 Mushima North

Tertiary Minerals plc announced additional laboratory analytical results from the recent Phase 4 drill programme at the Discovery Zone in Target A1, Mushima North Project in Zambia. 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. Depth extent of mineralisation increased with multiple drill holes ending in mineralisation. 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). 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). Additional laboratory analytical results expected over the coming weeks. A total of 39 (3,639m) Reverse Circulation 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. 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), 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. Additional certified laboratory results will be announced on an on-going basis as they become available. 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 were initially analysed on site using a portable X-Ray Fluorescence analyser for copper, zinc and silver. Analysis protocol included 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 procedure. Given the nature of the unprepared sample and point analysis, this method was 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 were 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) were inserted and will be monitored as part of the Quality Assurance Quality Control protocol. 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. The Company has previously reported a JORC-compliant Exploration Target for the Discovery Zone of between 15 and 30 million tonnes 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. 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.

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Tertiary Minerals Announces New Analytical Results from Phase 4 Infill Drilling At Discovery Zone Increases Depth Extent of Silver-Copper Mineralisation At Target A1 Mushima North

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