21 July 2025

Tertiary Minerals plc

 ("Tertiary" or the "Company")

 Drilling commences at Target A1, Mushima North Project, Zambia

Tertiary Minerals plc (AIM: TYM) is pleased to announce commencement of drilling at Target A1, a polymetallic (silver-copper-zinc) prospect. Target A1 is located on the Mushima North Project ("Mushima North" or the "Project") within the prospective Iron-Oxide-Copper-Gold region of Zambia.

Highlights:

·   Planned drilling programme of up to 1,500m Air Core/Reverse Circulation drilling.

·   Aim to test along strike and downdip continuations of mineralisation at Target A1, where drilling of this target in late 2024 returned drill intersections including (downhole widths, true widths unknown):

·   57m at 25 g/t Ag, 0.20% Cu, 0.15% Zn from 14m downhole (24TMNAC-004).

§ Including: 26m at 36 g/t Ag, 0.20% Cu, 0.20% Zn from 45m downhole.

·   65m at 23 g/t Ag, 0.14% Cu, 0.27% Zn from 9m downhole (24TMNAC-005).

§ Including: 5m at 73 g/t Ag, 0.16% Cu, 0.31% Zn from 69m downhole.

·   Target A1 is located only 28km east of the historic Kalengwa copper-silver mine which is under redevelopment.

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

"Previous initial drilling at Target A1 identified near surface polymetallic (silver-copper-zinc) mineralisation over a width of 350m and downhole intervals of up to 67m, but with many of the holes ending in mineralisation. This drill programme has been designed to follow-up on these highly encouraging drilling results and will not only test the surface footprint of the silver- and zinc-in-soil anomaly over a strike extent of some 1.6km and up to 300m wide, but also the downdip potential to a depth of up to 150m.  

"I look forward to updating shareholders on the drilling progress and results in due course."

Drilling Programme

A programme of up to 1,500m combined Air Core ("AC") and Reverse Circulation ("RC") drilling is planned as a series of east-west drill lines spaced approximately 250m apart (north-south). Holes will be collared approximately 100m apart along the east-west lines and drilled to a nominal depth of approximately 75m. Deeper holes (using RC) will also be undertaken in key areas to further understand the potential continuation of mineralisation at depth. The drill programme at Target A1 is designed to:

·    Test the silver- and part of the broader zinc-in-soil anomaly over approximately 1.6km of strike and up to 0.3 km width.

·    Test the depth extension of mineralisation in key areas to a depth of up to 150m.

·    Gain insights into the mineralisation styles and grade continuity.

The drill programme is being conducted by Ox Drilling which also completed the initial drill programme undertaken last year. The drill programme started on 18 July and will take approximately 2-3 weeks to complete. Samples will be initially analysed on site using a portable X-Ray Fluorescence ("pXRF") analyser for copper and zinc. Selected mineralised intervals will also be submitted for external assaying at a certified laboratory for a suite of elements, including silver, copper, zinc, bismuth, antimony and gallium.

Target A1

Target A1 is a large (3.1km by 1.7km) copper-in-soil anomaly with copper values up to 350ppm (via pXRF analyser) associated with a 1.7km by 0.5km zinc- and coincidental 1.3km by 0.3km silver-in-soil anomaly. Initial drilling over the silver- and zinc-in-soil anomaly (drill line 1) identified wide and thick silver mineralisation associated with low-grade copper and/or zinc mineralisation. 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.

Drilling results from the initial drilling programme undertaken in late 2024 include:

·    65m at 23 g/t Ag, 0.14% Cu, 0.27% Zn from 9m downhole (24TMNAC-005).

o  Including: 5m at 73 g/t Ag, 0.16% Cu, 0.31% Zn from 69m downhole.

·    66m at 26 g/t Ag, 0.13% Cu, 0.26% Zn from 13m downhole (24TMNAC-006P).

o  Including: 20m at 40 g/t Ag, 0.21% Cu, 0.40% Zn from 23m downhole.

·    57m at 25 g/t Ag, 0.2% Cu, 0.16% Zn from 14m downhole (24TMNAC-004).

o  Including: 26m at 36 g/t Ag, 0.20% Cu, 0.20% Zn from 45m downhole.

Mushima North Project

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

The Project lies 20km to the east of the Kalengwa copper mine in northwest Zambia, one of the highest-grade copper deposits ever to be mined in Zambia. In the 1970s, high-grade ore, average approximately 11% Cu, 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.

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 to any further agreement and there are no commercial restrictions for Tertiary, nor does FQM have a right of first refusal over the project. Further details can be found in the news release of 15 September 2022.

At the end of the summer 2024, Tertiary completed an initial 25 AC drill programme (1,274m) to test parts of geochemical (copper-in-soil) anomalies at Targets A1 and C1. This limited and shallow drilling has indicated wide downhole intervals of largely coincidental copper, zinc and silver mineralisation at Target A1.

Numerous other geochemical and/or geophysical targets (A2, B1, B2, B3, C2) are yet to be drill tested.

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 Zambia and Nevada, USA.

Figure 1. Geological map of the Mushima North Project showing the locations of the priority targets within the licence.

Figure 2. Location map of Target A1 showing soil sample results for copper and zinc, and the collar locations for the previous (late 2024) and upcoming drilling programme.