Cobra Resources PLC has reported positive results from metallurgical studies at its Boland Ionic Rare Earth Project, indicating potential for lower-cost recoveries. Testing of AMSUL diagnostic leaches below 0.5 molar achieved highlight recoveries, including 71% Neodymium + Praseodymium, 78% Dysprosium + Terbium, and 80% Samarium at pH 3 using 0.5 M AMSUL. Acid consumption tests confirmed low usage, with rates of 1.95 kg/t of sulphuric acid at pH 4.5 and 6.7 kg/t at pH 3.0; the pH 4.5 test also showed natural acid generation. A large-scale ISR column leach test using ~0.3M AMSUL at pH3 has commenced on a 55kg sample and is expected to take approximately 60 days.
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Natural acid generation observed in Boland mineralisation offers further potential to reduce recovery reagent costs
Commencement of large scale ISR column leach test to support offtake negotiations
Cobra (LSE: COBR), a mineral exploration and development company, is further advancing metallurgical studies at its 100%-owned Boland Ionic Rare Earth Project ("Boland") in South Australia in collaboration with the Australian Nuclear Scientific Technology Organisation ("ANSTO"). These studies are designed to further optimise the economics of in situ recovery ("ISR") of the Rare Earth Elements ("REEs") contained in the Boland mineralisation. The results of these studies will contribute to economic evaluation of an ISR programme under the terms of a planned Scoping Study.
· Improve production economics by minimising requirements for sulphuric acid, which is expected to be the greatest single operating cost input to REE ISR
· Maximise the recovery of high value REEs (Praseodymium, Neodymium, Samarium, Dysprosium and Terbium), being essential to the production of high-performance permanent magnets, both in a gross sense and in a relative sense as a proportion of total REEs contained in the Boland mineralisation
· Maximise product quality
· Shorten the residence time of the ISR mining process
· Reduce rehabilitation costs
The results of recent test work have been favourable in all respects, further reducing consumption of acid, whilst achieving high recoveries of REEs contained in the Boland mineralisation and potentially permitting an increase the enrichment of the valuable heavy REE fraction within a Mixed Rare Earth Carbonate ("MREC").
Rupert Verco, Managing Director of Cobra, commented:
"Cost efficiency is the principal enabler for market resilience, enabling strong margins during good times and market competitiveness in downturns. The ongoing positive results of our optimisation studies are supporting further reductions to the amount of sulphuric acid required to support scalable production.
The holy grail of REE supply chains is to produce an MREC which is enriched in the most valuable REEs and which accordingly minimises the processing required to produce these valuable REEs in pure form. The physical properties of the Boland mineralisation and the attractive capital and operating cost structure of ISR techniques offer Cobra an opportunity to adopt process parameters which minimise downstream REE separation costs."
Testing of (NH)SO "AMSUL" diagnostic leaches below the industry standard of 0.5 molar (M) highlight that acid requirements can be further reduced through the reduction of lixiviant molarity with the following highlight recoveries achieved:
Nd - Neodymium, Pr - Praesodymium, Dy - Dysprosium, Tb - Terbium, Sm - Samarium
Reducing the molarity of the lixiviant whilst retaining pH is achieved by maintaining the ratio of ammonium sulphate (base) with sulphuric acid. This maintains the quantity of free hydrogen ions while the lixiviant is diluted with water.
The United States Geological Survey (USGS) has recently released a revised draft of critical minerals. Within the revised draft, samarium has been ranked the highest in criticality. The Boland project has both good grades and recoveries of samarium. The list can be viewed here: 2025 Draft List of Critical Minerals | U.S. Geological Survey
Acid consumption tests confirm low acid usage, and highlight natural acid generation to further reduce acid usage
· Two acid consumption tests were performed, whereby the consumption rate determined by measuring the addition of AMSUL at a fixed acidity, over time
· During the pH 4.5 consumption test, additional acid was generated from within the Boland mineralisation, with the final pH finishing at 4.2, well below the intended test setpoint of pH 4.5
· Investigation indicates that traces of the mineral pyrite (iron disulphide), which occur naturally in the Boland mineralisation, were becoming oxidised during the consumption test, producing iron hydroxide and sulphuric acid, taking the pH below the intended pH test setpoint
· Further tests are now underway aiming to increase the oxidation of organic pyrite to ultimately increase natural acid production during ISR leaching
· This testing will also aim to oxidise and preferentially remove cerium before ISR leaching of REEs begins
· If successful, this work may indicate that acid costs will be even lower than previously expected and that some proportion of the light (less valuable) REEs, cerium and lanthanum, may be removed during a pre-conditioning phase of ISR, separate from the leach-production of MREC
Scaled column ISR test constructed to produce MREC for offtake negotiations and assessment
· Percolation of lixiviant through a 55kg ISR column containing a composite sample from three drillholes from across the Boland project has commenced using ~0.3M AMSUL at pH3
· This study is expected to take approximately 60 days
· Recovery rates of individual REEs will be evaluated during the ISR process, with separate liquors to be collected to evaluate the possibility of producing an MREC from both early stage (pH>4.5) and late stage (pH=3.0).
Reducing acid molarity is an alternate method to acid dilution. By reducing the acid moles per litre of lixiviant, the pH can be maintained through buffering. The results from this testing demonstrate that high recoveries of REEs can be maintained through the reduction of lixiviant molarity. Testing successfully shows that at pH3 the molarity can be reduced to 0.1M whilst maintaining recoveries of 68% Dy+Tb.
Figure 1: Recoveries at varying pH and molarities on the same composite sample
Note: Test conducted at 0.5M pH4 Diagnostic leach was run at pH 4.5
Throughout all tests, the ratio of impurities to REE solution concentrations remain relatively consistent, therefore economic evaluations will determine the optimised molarity to achieve the highest recoveries at the most economic level of acid consumption.
These tests aimed at confirming indicative acid consumption estimates calculated from diagnostic leach tests confirm low rates of acid consumption using 0.5M AMSUL. Furthermore, testing at weak acidities demonstrates acid generation from within the Boland mineralisation, with the final pH finishing at 4.2, well below the intended test setpoint of pH 4.5.
This provides a unique opportunity to catalyse acid generation through ISR preconditioning. An oxidation test will test the maximum potential of acid generation from the Boland ore sample, this will be tested by introducing an oxidant and measuring the pH over time.
Figure 2: Acid consumption test at pH 4.5 and the reduction in pH beyond the pH setpoint
At Boland, Cobra has discovered what it believes to be a unique, scalable instance where ionic rare earth elements - containing economically attractive grades of valuable heavy and magnet rare earths - occur in a permeable horizon confined between horizons of impermeable clay.
Bench scale ISR testing has confirmed that this mineralisation is amenable to ISR recovery techniques. ISR techniques are currently in use (and have been used successfully for decades) in geologically similar environments, to recover uranium in South Australia which maintains a well-established ISR regulatory system.
Results of Cobra's ongoing mineral recovery test work indicate that, with minor optimisation, ISR techniques will enable non-invasive and low-cost production of critical REEs from its discovery at Boland.
Follow this link to watch a short video of CEO Rupert Verco explaining the results released in this announcement: https://investors.cobraplc.com/link/yzjVxy
Further information relating to Boland and these results are presented in the appendices.
The person who arranged for the release of this announcement was Rupert Verco, Managing Director of the Company.
Information in this announcement relates to exploration results that have been reported in the following announcements:
· Exploration update: "Low-Cost Recoveries from Optimised Testing", dated 11 August 2025
· Exploration update: "Rare Earth ISR System beyond Boland", dated 4 August 2025
· Exploration update: "Favourable Boland Metallurgical Results", dated 21st July 2025
· Wudinna Project Update: "ISR bench scale update - Exceptionally high recoveries with low impurities and low acid consumption; on path to disrupt global supply
of heavy rare earths", dated 28 August 2024
· Wudinna Project Update: "ISR bench scale update -Further metallurgical success at world leading ISR rare earth project", dated 11 July 2024
The information in this report that relates to metallurgical results is based on information compiled by Cobra Resources and reviewed by Mr James Davidson who is Principal at Rendement and a Fellow of the Australian Institute of Mining and Metallurgy (F AusIMM). Mr Davidson has sufficient experience that is relevant to the metallurgical testing which was undertaken to qualify as a Competent Person as defined in the 2012 edition of the "Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves". Mr Davidson consents to the inclusion in this report of the matters based on this information in the form and context in which it appears.
Information in this announcement has been assessed by Mr Rupert Verco, a Fellow of the Australasian Institute of Mining and Metallurgy. Mr Verco is an employee of Cobra and has more than 17 years' industry experience which is relevant to the style of mineralisation, deposit type, and activity which he is undertaking to qualify as a Competent Person as defined in the 2012 Edition of the Australasian Code for Reporting Exploration Results, Mineral Resources and Ore Reserves of JORC. This includes 13 years of Mining, Resource Estimation and Exploration.
Cobra Resources is a South Australian critical minerals developer, advancing assets at all stages of the pre-production pathway.
In 2023, Cobra identified the Boland ionic rare earth discovery at its Wudinna Project in the Gawler Craton - Australia's only rare earth project suitable for in situ recovery (ISR) mining. ISR is a low-cost, low-disturbance extraction method that eliminates the need for excavation, positioning Boland to achieve bottom-quartile recovery costs.
In 2025, Cobra further expanded its portfolio by optioning the Manna Hill Copper Project in the Nackara Arc, South Australia. The project contains multiple underexplored prospects with strong potential to deliver large-scale copper discoveries.
In 2025, Cobra sold its Wudinna Gold Assets to Barton Gold (ASX: BDG) for up to A$15 million in cash and shares.
Regional map showing Cobra's tenements in South Australia
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· The Boland Project was discovered by Cobra in 2023. Mineralisation is ionically bound to clays and organics within palaeochannel sands within the Narlaby Palaeochannel
· Mineralisation occurs within a permeable sand within an aquifer that is saltier than sea water and is confined by impermeable clays
· ISR is executed through engineered drillhole arrays that allow the injection of mildly acidic ammonium or magnesium sulphate lixiviants, using the confining nature of the geology to direct and lower the acidity of the orebody. This low-cost process enables mines to operate profitably at lower grades and lower rates of recovery
· Once REEs are mobile in solution in groundwater, it is also possible, from an engineering standpoint, to recover the solution to surface via extraction drillholes, without any need for excavation or ground disturbance
· The capital costs of ISR mining are low as they involve no material movements and do not require traditional infrastructure to process ore - i.e. metals are recovered in solution
· Ionic mineralisation is highly desirable owing to its high weighting of valuable HREOs and the cost-effective method in which REEs can be desorbed
· Ionic REE mineralisation in China is mined in an in-situ manner that relies on gravity to permeate mineralisation. The style of ISR process is unconfined and cannot be controlled, increasing the risk for environmental degradation. This low-cost process has enabled China to dominate mine supply of HREOs, supplying over 90% globally
· Confined aquifer ISR is successfully executed globally within the uranium industry, accounting for more than 60% of the world's uranium production. This style of ISR has temporary ground disturbance, and the ground waters are regenerated over time
· Cobra is aiming to demonstrate the economic and environmental benefits of recovering ionic HREOs through the more environmentally aquifer controlled ISR - a world first for rare earths
Figure A1: Comparison between the Chinese and the proposed Boland process for ISR mining of REEs