30 May 2023

TERTIARY MINERALS PLC

("Tertiary" or "the Company")

HALF-YEARLY REPORT 2023

Tertiary Minerals plc is pleased to announce its unaudited interim results for the six-month period ended 31 March 2023.

Six-Month Operational highlights:

Tertiary continues to develop its mineral project portfolio, focused on copper opportunities in Zambia and copper and precious metals projects in Nevada.

Zambia

·      JV agreement signed with Mwashia Resources recognising the Company's 90% interest and right to purchase the remaining 10% interest in the Jacks Copper Project.

·      Jacks Copper Project soil sampling programme generated multiple copper soil anomalies with a peak value of 535ppm copper and high Cu:Sc ratios which can indicate hydrothermal copper sulphide and compare favourably with soil anomalies in the vicinity of various ore zones at current and past producing mines on the Copperbelt. Drill testing is planned.

·      Data transfer completed from First Quantum Minerals for the Mukai and Mushima North Copper Projects under a data sharing and technical cooperation agreement.

·      Resampling of 1970s drill hole RKN800 at Mushima North returned 33m grading 0.24% copper from 122m-155m downhole, including 9m grading 0.43% copper from 140m-149m. The drillhole ended in mineralisation grading 0.19% copper from 154-155m (EOH) and lies on the edge of an untested gravity anomaly defined and targeted for drilling by BHP for possible Iron-Oxide-Copper-Gold style mineralisation.

·      Extensive exploration targeting undertaken in preparation for the 2023 field season. Project Focus presentations published for the Mukai and Konkola West Projects. Mushima North Project Focus presentation to follow.

·      2023 field season commenced with soil sampling programme at the Lubuila Copper Project. In-field portable X-Ray Fluorescence (pXRF) analytical results indicate a large open-ended copper-in-soil anomaly defined over an area of approximately 1,000m x 680m with a peak copper value of 306 ppm and an average value of 125ppm Cu.

Nevada

Brunton Pass Copper Gold Project:

·      Results received from trenching programme showed wide intervals of low-grade copper skarn mineralisation including 27m grading 1,010ppm copper (0.1% Cu) in T7, open to the east, and 78m grading 473ppm copper in T8 also open to the east.

·      Results suggest the possible presence of a deeper porphyry copper target.

·      Two trenches testing the north and south ends of a 1.2km long zone of mercury/arsenic soil anomalies intersected substantial widths of hydrothermally altered rock with approximately 1,000 times background content of the gold indicator elements, arsenic and mercury. This zone is a compelling drill target for epithermal gold mineralisation.

FINANCIAL SUMMARY FOR THE SIX-MONTH PERIOD ENDED 31 MARCH 2023:

·      Operating Loss of £253,089 comprises:

o  Revenue relating to re-charged expenses of £75,944.

o  Less administration costs of £294,796 (including non-cash share-based payments of £14,145).

o  Pre-licence and reconnaissance exploration costs totalling £34,237.

·      Total Group Loss of £252,854 is after crediting interest income of £235.

·      Project expenditure of £115,162 was capitalised during the six-month period.

Funding and Cash Position:

·      In February 2023, the Company completed a fundraising with Peterhouse Capital Limited raising £300,000 before expenses.

·      The closing cash (and cash equivalent) position at the end of the period was £217,967.

CAUTIONARY NOTICE

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.

MARKET ABUSE REGULATION (MAR) DISCLOSURE

The information contained within this announcement is deemed by the Company to constitute

inside information as stipulated under the Market Abuse Regulations (EU) No. 596/2014 which

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 Interim Report for the six-month period ended 31 March 2023 and a summary of our principal activities which continue to be the identification, acquisition, and exploration of mineral projects prospective for copper and precious metals in Zambia and Nevada, USA, both stable democratic and mining friendly jurisdictions.

Copper is often overlooked in the rush for critical minerals for the green economy, yet it is used extensively in renewable power generation and electric vehicles. Long-term demand for copper is forecast to enjoy sustained growth as developed economies look to move towards net zero carbon emissions. Government-backed stimulus projects will add tailwinds to this, whilst infrastructure projects in developing economies will also pressure supply going forward.

In Zambia, this six-month reporting period spans the end of the 2022 dry season, the main field season, and the majority of the 2022-23 wet season where exploration access is largely restricted. We made the most of the wet season, however, by carrying out extensive data collection, evaluation and exploration planning for the 2023 field season, now underway.

This planning has been helped enormously by our data sharing and technical cooperation agreement with multi-national copper miner, First Quantum Minerals ("FQM"). FQM has provided extensive and valuable databases for our Mukai Project, which lies adjacent to FQM's Sentinel copper and Enterprise nickel mines, and for our Mushima North Project, where recent sampling of a 1970s drillhole has returned wide intervals of low-grade copper mineralisation, open at depth. These are exciting results as the drillhole lies on the margins of a significant untested gravity anomaly, now a target for Iron-Oxide-Copper-Gold ("IOCG") stye mineralisation.

The agreement with FQM has saved us hundreds of thousands of dollars in exploration expenditures and will harness the experience of FQM's technical staff for the benefit of our projects.

Shareholders can find extensive information on our Zambian Projects on our website where we have published project specific presentations on our Mukai and the Konkola West copper projects. Notably, our Mukai Project lies to the east of Arc Minerals' Zambian Copper Project where mining giant Anglo American recently signed a joint venture agreement with Arc Minerals and must spend US$88.5 million to earn a 70% interest in that project.

Our Konkola West Project lies adjacent to, and covers projected, deep, down dip extensions to, the Lubambe-Konkola mining complexes and where KoBold Metals is developing the large and high grade Mingomba deposit with backing from Microsoft's Bill Gates, Amazon's Jeff Bezos, Virgin's Sir Richard Branson, and mining giant BHP.

The Company's interests in Zambia also include the Jacks Copper Project where the Company completed an extensive soil sampling programme and we are delighted that this has defined a number of high priority copper soil anomalies. These are ready for drill testing and include anomalies associated with the original Jacks copper occurrence that we drill tested successfully in 2022 and where mineralisation is open at depth and along strike.

We anticipate that 2023 will be a busy year for the Company in Zambia with fieldwork planned on most of our projects in the country. We hit the ground running at the start of the 2023 field season having recently completed soil sampling at the Lubuila copper prospect. Preliminary field analysis using a pXRF analyser has defined a large open ended copper soil anomaly that now requires verification with conventional laboratory analysis.

Our objective is to define targets at all our Zambian projects in the next few months and to drill test priority targets within the current field season.

Our commitment to Zambia is illustrated by our recent co-sponsorship of a UK All Party Parliamentary Group for Critical Minerals reception held in honour of the Zambian President, His Excellency Hakainde Hichilema, who is ambitious for the growth of the Zambian copper mining industry and is improving the fiscal regime to encourage this.

We remain committed to testing our projects in Nevada and in this reporting period received results for a trenching programme at the Brunton Pass Project that has defined drill targets for copper skarn, porphyry copper and epithermal gold. However, Nevada is, at least in the short term, taking a backseat to Zambia where we have immediate expenditure commitments to the Government and to our local partner, Mwashia Resources. The two geographical regions are complementary for us in that exploration is not seasonal in most areas of Nevada.

Our activities during the period have been funded through existing cash resources and a share placing with our joint broker, Peterhouse Capital Limited, that raised £300,0000 before expenses, and the sale of a shareholding in TSX-V listed Aurion Resources.

We anticipate strong news flow in 2023 and are hopeful that this will result in a rerating of the Company by investors - a justifiable expectation highlighted by research initiated by our joint broker, SP Angel, and which can be accessed via our website. SP Angel has recommended the Company's shares as a "buy" and provides a comparison to other junior copper explorers across the AIM, TSX, and ASX markets which clearly emphasises the relatively undervalued nature of the Company.

Patrick L Cheetham

Managing Director

30 May 2023

Consolidated Income Statement

for the six-months' period to 31 March 2023

Consolidated Statement of Comprehensive Income

for the six-months' period to 31 March 2023

Company Registration Number 03821411

Consolidated Statement of Financial Position

at 31 March 2023