Highest grade Ag-Cu at Target A1, Mushima North

Tertiary Minerals plc (AIM: TYM) is pleased to announce drilling results for a further three holes from the Phase 2 follow-up drill programme at Target A1 at its Mushima North Project in Zambia ("Mushima North" or the "Project").

The new laboratory analytical results reveal the highest-grade silver and copper drill intersection to date and extend the mineralisation further to the north by approximately 100m. The thick near surface mineralisation now extends over an area 450m long and up to 400m wide, and remains open to the north/northwest, south/southeast and at depth.

Highlights:

Ø Highest-grade silver/copper mineralisation intersection to date on the project:

• 58m at 49 g/t Ag, 0.26% Cu and 0.16% Zn (72 g/t Ag equivalent or 0.94% copper equivalent) from 8m downhole (hole 25TMNAC-038).

§ Including: 20m at 86 g/t Ag, 0.44% Cu and 0.24% Zn from 46m downhole.

§ And: 9m at 124 g/t Ag, 0.73% Cu and 0.25% Zn (185 g/t Ag equivalent or 2.40% copper equivalent) from 57m downhole. The hole ended in mineralisation.

Ø Results include high-grade copper mineralisation (9m at 2.40% copper equivalent) and suggest the presence of a previously unknown zone of high-grade copper mineralisation, which is open to the north.

Ø Mineralisation footprint extended by a further 100m to the north, now over a 450 by up to 400m area, and remains open to the north/northwest, south/southeast and at depth.

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

"We are thrilled to report not only our best intersection of silver mineralisation so far on this project, but also higher-grade copper mineralisation with individual metre samples returning grades of up to 1.68% copper. Hole 25TMNAC-038 returned 58m at 72 g/t silver equivalent (or 0.94% copper equivalent) from near surface. This hole also included our best copper intersection so far at 9m at 2.40% copper equivalent (185 g/t Ag silver equivalent) from 57m downhole, with the hole ending in mineralisation. Significantly, the high copper and silver values are from the northern most drill line, so the mineralisation remains open to the north and at depth.

"These additional results have also extended the surface footprint of the mineralisation to the north by approximately 100m. The mineralisation footprint is now approximately 450m by 400m within a northwest-southeast orientation and remains open to the north/northwest, south/southeast and at depth. These results further support our bulk tonnage, open pit silver exploration model as well as the additional potential for copper and adds further credence to the significance of this discovery for the Company."

Phase 2 Drill Programme

As previously reported, the Phase 2 drill programme consisted of 1,116m of combined Air Core ("AC") and Reverse Circulation ("RC") drilling along a series of east-west drill lines spaced between 100m and 250m apart, north-south. Holes were collared approximately 100m apart along the east-west lines and drilled to the maximum depth possible at the time based on the drill rig capabilities and geological ground conditions (the bit refusal depth). The deepest drill hole in this programme was 99m and the average hole depth 70m. Combined Phase 1 and 2 drilling covers a surface footprint of approximately 1,680m by 550m.

The three drill holes now being reported, and described below, are located on two east-west drill lines, 8507275N and 8507150N. Drill Line 8507275N represents the most northern drill traverse drilled to date.

• 25TMNAC-038: Located on a two drill hole line with 25TMNAC-039. The drill hole was drilled to the east (inclined -60°) to a downhole depth of 66m. The hole was designed to test the continuation of the mineralisation to the north from drill line 8507150N.
• 25TMNAC-039: Located approximately 100m west of 25TMNAC-038 and drilled to the east (inclined -60°) to a downhole depth of 62m. The hole was designed to test the continuation of the mineralisation to the north from drill line 85072150N.
• 25TMNAC-040: Located approximately 100m west of 25TMNAC-026 and drilled to the vertically (inclined -90°) to a downhole depth of 61m. The hole was designed to test the continuation of the mineralisation to the east on drill line from drill line 8507150N.

To date, all significant silver values have been associated with copper and/or zinc. mineralisation. Analytical results are still awaited for a number of reconnaissance drill holes but, as these holes do not contain significant copper or zinc values by pXRF analysis and appear not to be on the interpreted trend of the mineralisation, significant silver results are not anticipated from these analyses.

Table 1. Phase 2 (Target A1) analytical results (three holes only, other analytical results from remainder of the drilling programme awaited). Equivalent grades ("Eq") are for illustrative purposes only.

Note to Table 1 and 2:

• Reported intersections (downhole, true widths unknown) are based on a cut-off grade of 10 g/t Ag. Intervals start and end with ≥10 g/t Ag and up to 3m consecutive of internal dilution has been allowed. All grades are averages weighted by sample length.
• Silver values are 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$4.5 lb, Ag: US$40 oz, Zn: US$1.2 lb and 100% recovery. No information on beneficiation recoveries is available at this stage. The metal equivalent values se are for illustrative purposes only.
• Gramme metres for silver are the silver values (g/t) multiplied by the intervals (m).

Target A1

Target A1 is a large copper-in-soil anomaly (3.1km by 1.7km) with copper values up to 302ppm (per Portable X-Ray Fluorescence, "pXRF") associated with a 1.7km by 0.5km zinc- and coincidental 1.3km by 0.3km silver-in-soil anomaly.

Phase 1 drilling in 2024 targeted the copper-in-soil anomaly and returned broad but generally low-grade copper mineralisation as reported in the news release dated 28 October 2024 (e.g. 57m at 0.2o% Cu from 14m downhole, hole 24TMNAC-004). Higher grade copper mineralisation within these broader zones was also returned (e.g. 6m at 0.58% Cu within 35m at 0.21% Cu, from 22m downhole, hole 24TMNAC-024). Drilling over the silver- and zinc-in-soil anomaly (drill line: 8506925N) identified wide and thick, near surface silver mineralisation associated with low-grade copper and/or zinc mineralisation.

The Phase 2 drill programme (1,116m), as discussed above, targeted the silver- and zinc-in soil anomaly. The silver mineralisation has now been confirmed to extend approximately 450m northwest-southeast and by 400m northeast-southwest and to a depth from near surface to 84m and it remains open-ended both to the north/northwest, south/southeast and at depth. The mineralisation at Target A1 is associated with a massive, haematitic and carbonaceous silty-sandy conglomerate. Where visible, copper mineralisation is in the form of secondary copper minerals malachite and chrysocolla. The mineralogical speciation of silver and zinc is yet to be determined. Elevated bismuth (up to 991 g/t), and the critical metals antimony (up to 0.21%) and gallium (up to 40 g/t) are also associated with the mineralisation in places.

Table 2. Selected silver intersections from Phase 1 and 2 drilling from Target A1. Equivalent grades ("Eq") are for illustrative purposes only. See Table 1 for notes.

Mushima North Project

The Project's western boundary lies 20km 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 (approximately 4 million tonnes at 5.2% copper and 40-80 g/t silver). In the 1970s, high-grade ore, reportedly averaging approximately 11% copper, was trucked for direct smelting at other mines in the Copperbelt. The Kalengwa mine is currently under redevelopment and is expected to produce 15,000 tonnes of copper annually.

Several prospective targets have been defined thus far within the Project based on reviews of historic geochemical and geophysical survey data against the current exploration model developed by Tertiary (Targets A1, A2, B1, B2, B3 and C1). At the end of the summer 2024, Tertiary completed an initial (Phase 1) 25 AC drill hole programme (1,274m) to test parts of geochemical (copper-in-soil) anomalies at Targets A1 and C1. This limited and shallow drilling indicated wide downhole intervals of largely coincidental copper, zinc and silver mineralisation at Target A1. The other geochemical and/or geophysical targets (A2, B1, B2 and B3) are yet to be drill tested.

Sampling, Analysis and QAQC

Samples were initially analysed on site using a pXRF analyser for zinc and copper. Analysis protocol included multiple point (three) 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 was used as a preliminary exploration technique to provide an approximate quantitative measure of copper and zinc mineralisation only.

Samples from selected drill holes based on the initial pXRF results were then sent to the independent laboratory ALS Global 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 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 based on silver, using a cut-off grade of 10 g/t Ag with up to 3m consecutive internal dilution and intervals starting and ending with ≥10 g/t Ag.

Figure 1. Location map of Target A1 showing soil sample results for copper and zinc and the collar locations for the 2024 and 2025 drill programme.

Figure 2. Drill cross-section 8507275N (location on Figure 1) showing analytical results for silver and selected copper values for drill holes 25TMNAC-038 and 25TMNAC-039. See Table 1 notes for further information.