Tertiary Minerals Reports Promising High-Grade Copper Zone in Phase 4 Drilling at Mushima North Target A1, Zambia

Strategic Location of Mushima North Project

Tertiary Minerals plc controls the Mushima North Copper Project via its subsidiary Copernicus Minerals Limited, which is 90% owned by Tertiary Minerals (Zambia) Limited and 10% by local partner Mwashia Resources Limited. Situated in Zambia’s Iron-Oxide-Copper-Gold belt, a geologically prospective mining region in southern Africa, Target A1 lies roughly 28 kilometres east of the historic Kalengwa copper-silver mine. This mine, active in the 1970s, produced ore with exceptionally high copper grades averaging about 11% Cu. Kalengwa is currently under redevelopment, aiming for annual copper production of 15,000 tonnes once operations resume.

The close proximity of Target A1 to this historic high-grade operation provides valuable geological context for Tertiary’s exploration. The company’s Licence 27068-HQ-LEL covers multiple additional geochemical and geophysical targets—A2, B1, B2, B3, and C2—mostly untested by drilling and located within a 12-kilometre radius of Target A1. This cluster positions the Mushima North Project as a district-scale exploration opportunity within a proven copper-producing region. Tertiary Minerals is an AIM-listed mineral exploration and development company focusing on energy transition metals, with principal activities targeting copper and precious metal resources in Nevada and Zambia.

Preliminary pXRF Results from Initial Drill Holes

The company disclosed preliminary pXRF data from samples of the first 12 drill holes at Target A1. These early Phase 4 results indicate a higher-grade copper zone in the northern part of the target, within the near-surface oxide mineralisation. The semi-quantitative pXRF analysis detected silver values up to 214 g/t alongside significant copper and zinc intersections across multiple holes. Tertiary Minerals cautioned that pXRF silver values are indicative and await confirmation by certified laboratory testing.

Highlighted drill intersections include 45 metres at 0.41% copper and 0.28% zinc from 12 metres downhole in hole 26TMNRC-045, featuring a 10-metre interval at 0.81% copper and 0.35% zinc. Hole 26TMNRC-049 yielded 55 metres at 0.32% copper and 0.29% zinc from 26 metres downhole, including 25 metres at 0.36% copper and 0.28% zinc. Hole 26TMNRC-053 recorded the longest intersection of 73 metres at 0.29% copper and 0.38% zinc from 25 metres downhole, with a notable 20-metre section at 0.48% copper and 0.65% zinc. All thicknesses are downhole measurements; true widths are pending further geometric analysis.

Exploration Target Alignment with Geological Model

The Phase 4 drilling aims to support the definition of a Joint Ore Reserve Committee (JORC) Mineral Resource Estimate for Target A1. The company previously announced a JORC-compliant Exploration Target of 15–30 million tonnes averaging 40–60 g/t silver equivalent. This target describes a near-surface, tabular oxide zone approximately 500 metres long, 300 metres wide, and up to 75 metres thick, based on a 25 g/t silver equivalent cut-off grade. Preliminary Phase 4 infill drilling results support the current oxide mineralisation extent within this target while intersecting higher-grade copper and potential silver mineralisation in the northern section.

Richard Belcher, Managing Director of Tertiary Minerals, stated: "We are pleased to report initial pXRF results for copper and zinc from the first Phase 4 drill holes, where infill drilling is underway to aid JORC Mineral Resource delineation. These results suggest the higher-grade copper and silver mineralisation seen in drill hole 25TMNRC-043 (13m at 77 g/t silver and 1.46% copper) during the previous programme likely continues." He added, "This is an encouraging start, and we eagerly await independent laboratory analyses. Drilling is ongoing, and we will provide further updates as the programme advances." The company notes mineralisation at Target A1 remains open to the northwest, southwest, and at depth, with full geometry yet to be defined.

Phase 4 Drilling Programme Details and Methodology

The Phase 4 reverse circulation drilling campaign is a systematic effort to delineate mineralisation extent and grade distribution at Target A1. To date, 22 holes totaling 2,175 metres have been completed out of an approximate 4,000-metre planned programme. Drilling is arranged in east-west lines spaced about 100 metres apart north-south, with holes spaced roughly 50 metres along each line and drilled to vertical depths up to 125 metres, based on rig capacity. The programme is designed in two passes to allow preliminary results to inform ongoing drilling and geological model updates.

Sampling is conducted at one-metre intervals with two subsamples taken per interval via riffle splitting: one for potential laboratory analysis and one for reference. Initial on-site pXRF analysis targets copper, zinc, and silver, averaging two analyses per sample and including Certified Reference Material, blanks, and duplicates as part of internal Quality Assurance. The company acknowledges that pXRF on unprepared samples offers approximate quantitative copper and zinc measures only. Results from an additional 10 holes are expected imminently, with ongoing announcements planned.

Independent Laboratory Testing and Accessory Metal Assessment

Selected drill samples, based on pXRF results, are submitted to ALS Global in South Africa for comprehensive multi-element analysis using a four-acid digest method (ME-ICP61). Elements tested include silver, copper, zinc, bismuth, antimony, and gallium. Quality assurance protocols involve Certified Reference Material, duplicates, and blanks to ensure data reliability and industry standards. Certified results are anticipated in the coming weeks.

Beyond copper and zinc, the Phase 4 programme investigates accessory metals linked to Target A1 mineralisation. Previous drilling revealed elevated bismuth (up to 991 g/t), antimony (up to 824 g/t), and gallium (up to 40 g/t) levels. Their economic potential remains under evaluation. The company notes pXRF silver data is currently insufficiently reliable for average grade estimation, emphasizing the importance of laboratory confirmation. The potential transition from near-surface oxide to underlying sulphide mineralisation remains untested.

Technical Cooperation with First Quantum Minerals

The Mushima North Project benefits from a technical cooperation agreement with First Quantum Minerals Limited (FQM), a leading global copper and nickel producer. This agreement grants Tertiary Minerals access to FQM’s historic exploration data and technical expertise on the area’s mineralisation and structural controls. The non-binding arrangement imposes no commercial obligations or rights of first refusal on Tertiary Minerals.

This collaboration enables Tertiary Minerals to leverage FQM’s institutional knowledge while preserving exploration independence and commercial flexibility. Established in September 2022, the agreement supports geological understanding and project advancement. Both parties retain strategic and commercial autonomy under this pragmatic framework.

Competitive Edge of Target A1’s Polymetallic Mineralisation

Target A1 is a polymetallic prospect featuring silver, copper, and zinc mineralisation within a near-surface oxide zone, offering multiple revenue streams. The silver content, with Exploration Target grades of 40–60 g/t silver equivalent, is a significant component. Previous drilling demonstrated exceptional silver grades, such as hole 25TMNRC-043’s 13 metres at 77 g/t silver and 1.46% copper, confirming higher-grade silver zones.

Elevated accessory metals like bismuth, antimony, and gallium add potential value, given their applications in semiconductors, solar photovoltaics, and advanced energy transition technologies. The near-surface oxide mineralisation may offer cost and environmental advantages over deeper sulphide deposits. The deposit’s tabular geometry—approximately 500 metres long, 300 metres wide, and up to 75 metres thick—suggests suitability for open-pit mining if economically viable.

Geological and Jurisdictional Risks in Zambia

Zambia is a stable, democratic mining jurisdiction with established infrastructure and regulatory frameworks. However, mineral exploration carries inherent geological and commodity price risks. The Mushima North Project lies within Zambia’s iron-oxide-copper-gold belt, a copper-endowed region where exploration success is not guaranteed. Converting the Exploration Target into a Mineral Resource and economic mining reserve depends on continued positive drilling, geological modelling, and viable commodity prices.

Commodity price volatility for copper and silver impacts project economics and investment appeal. The Phase 4 drilling is early-stage, with only 22 of approximately 4,000 metres completed. While preliminary pXRF results are promising, laboratory confirmation is pending. Additional risks include regulatory changes, social licence considerations, and permitting variability common to African mining exploration. The technical cooperation with FQM offers data and consultation benefits but no commercial or operational guarantees.

Strategic Focus on Energy Transition Metals

Tertiary Minerals strategically focuses on energy transition metals, with Mushima North as a key copper asset. Copper demand is expected to rise significantly due to renewable energy infrastructure, electric vehicles, and grid modernization globally. Zambia’s established copper mining culture and export infrastructure make it an attractive jurisdiction for copper exploration and development amid this secular demand.

The Phase 4 drilling aligns with Tertiary’s goal of advancing copper and precious metal discoveries in mining-friendly regions. Target A1’s near-surface, polymetallic mineralisation positions it as a potential near-term development opportunity compared to deeper or more complex deposits. If a JORC Mineral Resource Estimate confirms economic viability, Mushima North could advance toward development, unlocking shareholder value through financing, partnerships, or other mechanisms. The company’s systematic infill drilling reflects a professional approach to building data confidence for resource estimation and pre-feasibility assessment.