Cobra Resources Defines Scalable Rare Earth System at Head Prospect

• Cobra has drilled 74 holes for approximately 3,200 metres at Boland and Head to support a maiden Mineral Resource Estimate (MRE) for its ionic rare earth element (REE) mineralisation.
• A continuous high-grade flank of approximately 5 kilometres has been defined at the Head prospect, with mineralisation remaining open to the north and south.
• Net Acid Production Potential (NAPP) estimates indicate that natural acid generation exceeds acid consumption in high-grade zones, thereby reducing the sulphuric acid required for in situ recovery (ISR).
• Particle-sizing analysis supports productive permeabilities for ISR, with the data to feed permeability inputs into the MRE.
• The optimised Mixed Rare Earth Carbonate (MREC) product grades 58.83% total rare earth oxide (TREO), with actinium the only radionuclide above targeted limits, and actinium suppression testing is underway.

Company Overview

Cobra Resources (LSE: COBR) is a South Australian critical minerals developer advancing assets across all stages of the pre-production pathway. In 2023, the company identified the Boland ionic rare earth discovery at its Wudinna Project in the Gawler Craton, described as Australia's only rare earth project suitable for in situ recovery (ISR) mining, a low-cost, low-disturbance method that removes the need for excavation. In 2025, it optioned the Manna Hill Copper Project in the Nackara Arc and sold its Wudinna Gold Assets to Barton Gold for up to A$15 million in cash and shares.

Drilling Programme & Results

Cobra has completed 74 drillholes for approximately 3,200 metres across the Boland and Head prospects, a programme designed to support a maiden Mineral Resource Estimate (MRE) for its aquifer-hosted ionic rare earth element (REE) mineralisation, which is amenable to low-cost ISR. Approximately 80% of results have been received, with the remainder due in the coming weeks. At Head, the drilling has defined a continuous high-grade flank of approximately 5 kilometres, with mineralisation remaining open to the north and south.

Significant intersections at Head include 5.95 metres at 1,232ppm total rare earth oxide (TREO) from 27.8 metres, which contained 1.45 metres at 4,186ppm TREO, and 2.17 metres at 1,783ppm TREO from 30.4 metres. Other holes returned 1.06 metres at 3,607ppm TREO from 18.6 metres and 3.8 metres at 1,322ppm TREO from 26.1 metres. At Boland, intersections include 2.7 metres at 1,458ppm TREO from 33.3 metres and 1.05 metres at 1,004ppm TREO from 32.6 metres.

Mineralisation at Head occurs within three formations amenable to ISR: the shallow, permeable Narlaby sands; the smectite-rich Garford clays with sandy interbeds; and the confined, permeable Pidinga sands. Results from a further 12 holes at Head remain outstanding, and samples from the Garford and Narlaby formations are being analysed for incorporation into the MRE.

Confined Palaeochannel Setting

The Wudinna mineralisation sits within palaeochannel formations confined by impermeable layers, allowing a confined ISR process in which the injected lixiviant remains bound to the mineralised zone. This improves process control and reduces environmental risk.

High sand content in the host formations provides the permeability needed for ISR, avoiding the excavation and clay-handling costs associated with heap-leach or vat-leach processing. High-grade mineralisation occurs on the margins of the main incised channel at Boland and on the eastern margin of the Yaninee Channel at Head, with broader low-grade zones inside the channel returning recoveries of more than 80% at very low acid levels.

Managing Director of Cobra Resources, Rupert Verco, is direct about the system the drilling has defined:

“Results from the Head Prospect indicate the presence of a significant system that remains open to the north and south. The prospect contains all the right features to enable cost-efficient ISR: aquifer confinement, acid generation, and highly permeable mineralisation. It highlights that the target geology within the Pidinga formation is likely to be regionally extensive across the 3,200 square kilometres of palaeochannel systems contained within the company's landholding.”

That regional extent keeps the channel system as the focus of continued resource definition.

Acid Generation & Extraction Costs

A defining feature of Cobra's palaeochannel mineralisation is its high sulphide and low carbonate content. Pyrite in the system can be oxidised to produce sulphuric acid, the primary reagent used to recover ionic rare earths, while carbonates such as calcite and shell grit consume acid. Net Acid Production Potential (NAPP) estimates compare the maximum potential acidity of each sample against its neutralising capacity, calculated from total sulphur, total carbon, and total organic carbon.

Across the continuous high-grade zones at both Head and Boland, NAPP estimates show that natural acid generation exceeds acid consumption, with samples demonstrating a maximum potential acidity of 60 kilograms of sulphuric acid per tonne. Because the sulphuric acid supply chain is a primary cost in rare earth extraction and is critically impacted by current global events, generating acid in place reduces both production cost and supply risk.

Permeability & Sizing

Permeability is a key enabler of ISR, and Cobra has analysed particle-size distributions at numerous intersections to support permeability calculations within the MRE. Partial results support estimates of productive transmissivity needed for ISR production, and results from both Boland and Head indicate productive permeabilities through the mineralisation intersected in the Pidinga formation.

The sizing data is being compared against field hydrology results to model the mineralised formations more broadly, and additional samples from the Garford and Narlaby formations are being analysed to calculate their permeabilities.

Product Specification & Radionuclides

In January, Cobra reported an optimised Mixed Rare Earth Carbonate (MREC) product grading 58.83% TREO, with a high proportion of magnet and heavy rare earths. Neodymium accounts for 27.5% of TREO and praseodymium 6.7%, while dysprosium and terbium account for 3.8% and 0.7% respectively, and heavy rare earths make up 42.9% of the total.

Radionuclide analysis of the optimised product showed low levels for all radionuclides except actinium, which exceeded the targeted limits. The company and its advisers consider this addressable and have begun testing with the Australian Nuclear Science and Technology Organisation (ANSTO), covering ISR pre-conditioning, pH control, and actinium suppression.

Next Steps

Cobra expects the remaining drilling results in the coming weeks and is undertaking further permeability, metallurgy, and acid-generation testwork on the Garford and Narlaby formations for inclusion in a maiden MRE at Boland and Head. The company is also in commercial discussions over increased MREC volumes from a field trial targeted for early 2027.

Verco frames the economic ambition:

“The opportunity we are developing is truly unique. This is the first REE project of its kind in which a resource will incorporate modelling of key economic factors for permeability and acid generation. When coupled with the very low capital and operating costs of ISR, this changes the industry expectations of what is economically possible and positions Cobra competitively at the bottom of the cost curve. Meanwhile, our diamond core drilling programme is progressing well at the Manna Hill copper project, and we look forward to announcing updates on this as well as further work towards a maiden rare earth MRE at Boland and Head.”

A maiden resource at Boland and Head would convert the drilling, acid-generation, and permeability datasets into Cobra's first formal estimate of the project's scale.

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