27 June 2025

("Tertiary" or "the Company")

HALF-YEARLY REPORT 2025

Tertiary Minerals plc is pleased to announce its unaudited interim results for the six-month period ended 31 March 2025 and to provide an update on operational progress since the release of the Company's Annual Report in early February 2025.

A copy of this report is also available on the Company's website, www.tertiaryminerals.com.

OPERATIONAL HIGHLIGHTS

During the reporting period, the Company has continued its focus on copper and precious metal exploration in Zambia and Nevada, USA, and in particular on its exciting Mushima North Project in Zambia

Mushima North Project (Silver-Copper-Zinc, Zambia)

·      Results of analysis of 2024 drill samples reveal thick intervals of near surface silver mineralisation associated with broader intervals of previously reported copper and zinc mineralisation at Target A1 including:

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

Ø 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.)

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

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

Ø 37m at 24 g/t Ag, 0.11% Cu, 0.34% Zn from 46m downhole (24TMNAC-008P).

(Including: 19m at 27 g/t Ag, 0.09% Cu, 0.16% Zn from 64m downhole.)

·      Mineralisation is open-ended and the majority of holes end in mineralisation along drill line 1.

·      Mineralisation extends across a width of at least 250m along drill line 1 and is associated with a silver-in-soil anomaly (1.3 by 0.3km), which is coincidental with a broader 1.7 by 0.5km zinc-in-soil anomaly, and a kilometre-scale copper-in-soil anomaly.

·      Mushima North represents the Company's highest priority sole funded project in Zambia. Further drilling is warranted and is expected to commence in the next few weeks.

Konkola West Project (Copper, Zambia)

·      Silicon-valley funded KoBold Metals is earning into the Project by completing two deep drill holes for a minimum of 2,000m for an initial 51% ownership of the Project.

·      Targeting deep extensions to the 15km long large Konkola-Musoshi line of copper mines.

·      First drill hole extended to a depth of 2,711m, the deepest exploration borehole ever drilled in Zambia, but terminated short of target due to technical issues.

·      Exploration continues and the second drill hole is in progress.

Mukai Project (Copper, Zambia)

·      Exploration is under management of First Quantum Minerals, where First Quantum Minerals has an initial 24-month due diligence period during which it is required to spend a minimum of US$1.5 million (US$0.5 million in Year 1) on exploration expenditure, prior to advancing to the earn-in stage.

·      Results from three scout drill holes drilled in late 2024 to test the western Tirosa sedimentary basin and a copper-in-soil geochemical anomaly intersected near surface anomalous copper mineralisation, including:

Ø 0.12% Cu over 3.8m from 1.6m downhole (TARDD0023).

Ø 0.17% Cu over 2m from 4m downhole (TARDD0024).

·      Near surface and thick intervals of anomalous (>500 ppm) nickel mineralisation also intersected, including: 558 ppm Ni over 63.1m from 10m downhole.

·      Exploration programme/next steps currently under review.

Brunton Pass Project (Copper-Gold-Silver, Nevada USA)

·      Results received from four reverse circulation percussion drill holes completed in late 2024:

Ø All four holes intersected thick intervals containing anomalous copper values associated with fresh and oxidised pyrite and trace chalcopyrite.

Ø Cumulative drill thicknesses up to 210m grading 170ppm copper (24TBPRC002) with values up to 0.19% copper over 1.53m.

Ø Anomalous copper values extend to at least 212m vertical depth, in an area 630m east-west and 560m north-south.

·      Deeper diamond drilling is justified to test the core of the target geophysical anomaly.

Storuman Project (Fluorspar, Sweden)

·      Storuman Fluorspar Project contains combined Indicated and Inferred Mineral Resources of 27.7 million tonnes grading 10.2% fluorspar. Fluorspar is an EU designated critical mineral.

·      Detailed submission made in March 2025 to supplement the September 2024 appeal against the Mining Inspector's decision to refuse the Company's mining concession application. The Company awaits a response.

FINANCIAL SUMMARY FOR THE SIX-MONTH PERIOD ENDED 31 MARCH 2025:

·      The Group Operating Loss after crediting interest income of £10 was £248,460 and comprises:

Ø Revenue of £100,839; less administration costs of £339,832 (which includes non-cash share-based payments of £1,550).

Ø Pre-licence and reconnaissance exploration refund totalling £2,788.

Ø Impairment of deferred exploration asset totalling £12,255.

·      Project expenditure of £342,348 was capitalised during the six-month period.

Funding and Cash Position:

·      The Company's closing cash (and cash equivalents) position at the end of the period was £93,502.

·      Revenue during the reporting period comprises Sunrise Management recharges of £67,436, Sunrise Overhead recharges of £9,787 and Other Revenue of £23,626, including interest.

·      The Company relies upon periodic capital fundraisings until such time as regular cashflow can be derived either from the sale or development of the Company's projects. Following the end of the reporting period, on 6 June 2025, the Company announced that it had raised £350,000 through a placing of new ordinary shares.

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.

Chairman's Statement

I am pleased to present our unaudited interim results for the six-month period ended 31 March 2025 and to update on operational progress since the release of our Annual Report in early February 2025.

In this period, we have continued sole funding of our exciting Mushima North silver-copper-zinc discovery in Zambia whilst our joint venture partners continue to fund substantial expenditures on our Konkola West and Mukai copper projects in Zambia.

Operational Progress

Zambia

Mushima North

Much of our news flow since the publication of our last Annual Report has been in connection with the Mushima North Project where we have been reporting unexpectedly high silver results from assaying of previously reported copper and zinc mineralisation.  These results show that thick intervals of silver mineralisation are commonly associated with zinc and/or copper at Target A1, including 26 g/t silver over 66m from 13m downhole (24TMNAC-006P). Polymetallic mineralisation is now intersected in multiple 50m spaced holes. With only a small section of the soil geochemical anomaly tested so far (the initial drill programme was <1500m), and many of the holes ending in mineralisation, including 73 g/t Ag over 5m at the end of hole 24TMNAC-005, we feel we have only just scratched the surface of this exciting target. 

Mukai

Evaluation of our Mukai Copper Project was a priority for First Quantum Minerals (FQM) in 2024 due to the Company's earlier delineation of a substantial copper-in-soil anomaly in prospective stratigraphy, adjacent to its Trident mining complex. Recent results from three scout holes drilled by FQM in late 2024 show near surface anomalous copper and nickel mineralisation. Given the limited drilling completed to date, and with only one hole testing the target units and much of the soil anomaly untested, we believe there is still potential upside to this project. We are currently in discussions with FQM on the next steps for exploration. FQM has reported that the drilling and other preparatory work completed reaches their minimum expenditure of US$0.5 million for Year 1 as part of the 24-month due diligence period.

Konkola West

At Konkola West, our earn-in partner, KoBold Metals, is continuing its joint venture earn-in by sole funding the second of two deep drill holes targeting potential deep extensions to the copper ore-shale being mined at the nearby world-class Musoshi, Lubambe and Konkola Mines.

Drilling of the first hole, KWDD001, was terminated at a depth of 2,711m due to technical difficulties and prior to reaching the targeted ore-shale horizon. Nevertheless, the geological data collected as part of the drilling has been instrumental in better understanding the previously unknown geological architecture of the host sedimentary basin and has been used to inform the siting of the second drill hole which is now in progress. KWDD001 is believed to be the deepest mineral exploration drill hole to ever be drilled in the Zambian Copperbelt and marks a significant milestone within the industry. 

Nevada

Brunton Pass

In late 2024 we completed a short (~890m) drilling programme, our first at Brunton Pass. This confirmed that the main target's geophysical anomaly is due to sulphide mineralisation and thick intervals of anomalous copper. Mercury and arsenic, indicators for precious metal mineralisation, have been found in association with this anomaly over a wide area. However, only the peripheral parts of the IP geophysical anomaly have been intersected at depth so far and the stronger parts of the anomaly remain untested.  Results to-date suggest we may have drilled within the halo of a porphyry-copper system and that deeper drilling is justified to test the unexamined portions of the IP anomaly.

Sweden

Storuman Fluorspar Project

Following the Mining Inspector's latest decision to refuse the Company's mining concession for the Storuman fluorspar deposit, a detailed submission was submitted to the Swedish Government in March 2025 to supplement the Company's earlier appeal against that decision. Fluorspar is considered a critical minerals by the EU and the US, and Storuman hosts a large JORC compliant mineral resource. We believe the Company has a strong case and we remain optimistic for a positive outcome. The Swedish Government has indicated that it may take up to 12 months for a decision to be made.

Corporate Developments

In February this year we were pleased to announce the appointment of our new Managing Director, Dr. Richard Belcher. Richard, a geologist with a Masters in Finance, brings a wealth of knowledge and experience across a range of commodities, with a strong emphasis on Africa where his extensive field experience includes significant work in Zambia.

We have recently engaged Bromham Communications & Investment Limited to support our investor relations outreach efforts and provide access to the StockBox Investor Platform. We also continue to work with Mining & Metals Research Corporation to enhance our social media presence. A number of interviews and updates are now available through these channels and on our website.

Looking Forward

Our focus for the remainder of the year will be on Zambia and, now that the wet season is over and with a fundraising behind us, we are keen to start a follow up drilling programme at our Mushima North Project where our ambition is to scope out the size and grade of the newly discovered silver-copper-zinc at the A1 target.

In the meantime, we eagerly await the progress of the second drill hole being drilled at Konkola West. We are incredibly excited for Tertiary to be involved in this extraordinary project and remain extremely positive on the potential future outcomes.

Patrick L Cheetham

Executive Chairman

27 June 2025

Consolidated Income Statement

for the six-month period to 31 March 2025

Consolidated Statement of Comprehensive Income

for the six-month period to 31 March 2025

Company Registration Number 03821411

Consolidated Statement of Financial Position

at 31 March 2025