Chilwa Minerals Limited (ASX: CHW) — Rare Earth Elements Confirmed in Clays Beneath Mposa HMS Deposit, Malawi

26 June 2026

Price Sensitive Announcement $

Highlights:

• REE confirmed in basal clays — assays from 200 mineral sands drilling samples have confirmed rare earth element mineralisation in clay intervals directly beneath the Mposa heavy mineral sands deposit, returning total rare earth oxide (TREO) grades averaging 525ppm
• Consistent, widespread grades — 114 of 200 samples (57%) returned greater than 500ppm TREO and 17 samples (8.5%) exceeded 750ppm, with a peak grade of 987ppm TREO in hole MPOSD509, pointing to broadly consistent mineralisation across an approximately 8km corridor
• Directly beneath HMS deposits — the mineralised clays were sampled during regular HMS drilling and are derived from the HMS deposits’ Basal Clay interval
• Depth testing required — samples are collected from the top of a clay unit known to extend to depths of tens of metres, not yet systematically sampled
• Enriched in magnet rare earths — the in-situ basket carries high-value magnet rare earths, with magnet rare earth oxides (Nd, Pr, Dy and Tb) averaging approximately 21% of TREO and heavy rare earth oxides approximately 19.6% of TREO
• Ionic-adsorption potential to be tested — whether the rare earths occur in a recoverable, ionic-adsorption clay form has not been established and will be assessed by metallurgical desorption test-work at ANSTO in Sydney
• A stacked critical-minerals opportunity — the REE-bearing clay horizon sits immediately beneath the Mposa HMS deposit, co-located on the Company’s contiguous licence and raising the potential for heavy mineral sands and rare earths to be drawn from a single mine site

Overview:

Chilwa Minerals has uncovered a potentially significant new value driver beneath its existing Mposa heavy mineral sands deposit in southern Malawi, with assay results confirming widespread rare earth element mineralisation hosted in clays directly underlying the HMS horizon.

The results stem from routine HMS sonic drilling, which required passing through approximately 2m of “Basal Clay” marking the limit of mineral sands prospectivity. Testing of that clay interval across the approximately 8km Mposa corridor returned an average TREO grade of 525ppm, with results ranging up to 987ppm and the majority of samples (57%) exceeding the 500ppm threshold — pointing to a genuinely widespread, near-surface clay-hosted REE system rather than an isolated anomaly.

Particularly encouraging is the composition of the rare earth basket: magnet rare earth oxides neodymium, praseodymium, dysprosium and terbium collectively average around 21% of TREO, with heavy rare earth oxides making up approximately 19.6% of the total — a proportion characteristic of clay-hosted systems and significant given these elements carry the majority of rare earth basket value. However, the critical unknown remains whether the rare earths are present in a recoverable, ionic-adsorption clay (IAC) form — the low-cost, ambient-temperature leachable style that supplies much of the world’s heavy and magnet rare earths. Geochemical indicators to date are not diagnostic either way, with cerium anomalies weak and variable across the dataset. Resolving this question will require ammonium-sulfate desorption test-work, now planned at ANSTO in Sydney.

Perhaps the most compelling aspect of the discovery is its location: the REE-bearing clay horizon sits immediately beneath Chilwa’s established Mposa HMS deposit, raising the genuine prospect of a dual-commodity mine site — heavy mineral sands extracted at surface, with rare earths recovered from the clays beneath. This co-location carries meaningful potential benefits in shared infrastructure, permitting pathways and capital costs should the ionic-adsorption testwork prove successful.

With the clay unit known to extend to depths of tens of metres and not yet systematically sampled at depth, and with the substantially larger Mpyupyu HMS deposits on the same licence also known to be underlain by clays, Chilwa now has a clear program to test the scale of this opportunity across its broader Lake Chilwa licence area.

Company Notes:

Chilwa Minerals’ Managing Director, Cadell Buss, commented: “These are exciting results for Chilwa. We set out to test whether the clays beneath our Mposa mineral sands deposit carried rare earths, and the assays have come back confirming widespread REE mineralisation — averaging 525 ppm TREO and consistently above 500 ppm across an eight-kilometre corridor. Clearly there is a lot of work ahead of us, notably leachability testwork, however the results are especially compelling in terms of co-location with our mineral sands deposits. It would essentially be a dual-commodity mine —with heavy mineral sands at surface and rare earths in the clays beneath. The basket is encouraging too, with the valuable magnet rare earths — neodymium, praseodymium, dysprosium and terbium — making up around a fifth of the total. The real prize would be if these rare earths prove to be held in an ionic-adsorption clay form, the style behind some of the world’s lowest-cost rare earth operations — economics in these deposits is an interplay of leachability and REE value, ie recoverable Heavy Rare Earth component. Measuring how much of the contained REE is recoverable by simple leaching is the key question our upcoming test-work is designed to answer. This is a reconnaissance result, not yet a Mineral Resource, but it opens yet another genuine new front for Chilwa. We will move quickly through desorption test-work to determine whether Mposa as well as the other HMS deposits on the license, notably the substantially larger Mpyupyu deposits, can host a clay-hosted rare earth opportunity alongside (ie underneath), its mineral sands endowment.”

About Chilwa Minerals Limited (ASX: CHW):

Chilwa Minerals is a Southern Malawi-focused critical minerals explorer advancing four concurrent programmes within its Lake Chilwa licence: a niobium-REE-tantalum-gallium discovery at the Nakombe alkaline intrusive target; carbonatite-hosted REE exploration across the broader licence package; a Heavy Mineral Sands project in development along the northern and western shores of Lake Chilwa; and an emerging ionic clay REE programme targeting leachable rare earth elements within the weathering profile of the Chilwa Alkaline Complex. The Company is uniquely positioned with multiple critical mineral exposures within a single contiguous licence area in one of Africa’s most prospective underexplored alkaline provinces.

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