Cobra Resources' Boland Four-Variable ISR Case: 8 Things You Need to Know

Project Overview

Boland is a 100%-owned ionic rare-earth element project advancing through In-Situ Recovery on EL7074 within the Wudinna Project, Gawler Craton, South Australia. The project is held by LAM Wudinna, a wholly-owned subsidiary of Cobra Resources (LSE: COBR). Alcrest Royalties Australia holds a 1.5% Net Smelter Return royalty over the project tenements, and a Native Title Agreement is in place with the Barngarla people.

Cobra restructured its asset base in 2025, divesting the Wudinna Gold Assets to Barton Gold for up to A$15 million in cash and shares. The company is entitled to 6.45 million shares in Barton Gold upon final settlement of the transaction, plus up to A$9.5 million in further future payments. Cobra's wholly owned subsidiary also holds a binding option agreement to acquire 100% of Hamelin Gully, which holds the Manna Hill Copper Project.  

The current programme is a 74-hole resource-definition campaign across the Boland and Head prospects, now completed, and designed to support an initial Mineral Resource Estimate (MRE) and economic evaluation.

1. The Confined In-Situ Recovery Method at Boland

Boland uses a confined In-Situ Recovery (ISR) method that does not involve excavation or heap leaching. Lixiviant is circulated through a confined, hypersaline aquifer, dissolving rare-earth elements and returning them to the surface for processing. In this system, permeation is reliant on aquifer permeability rather than gravity.

Four variables, grade, permeability, metallurgy, and natural acid generation, interact to govern both operating cost and wellfield performance.

2. The Four-Variable Framework

The resource-definition drilling programme is structured to generate quantifiable data on all four variables simultaneously, enabling integrated modelling within the MRE and the subsequent Scoping Study.

Heavy rare-earth enrichment indicates ionic mineralisation and directly supports a higher-value product. Permeable sand horizons maximise wellfield spacing and reduce the duration of ISR extraction cycles. Metallurgy governs acid consumption: higher ionic proportions in the orebody require less acid, reducing both operational cost and impurity levels. Natural acid generation from organic pyrite within the Pidinga and Garford formations reduces the need for external sulphuric acid, cutting a primary cost input.

3. Grade & the Initial Assay Results

Preliminary results from 14 resource-definition holes at Boland provide encouraging observations for the project model's ionic rare-earth grade assumptions.

Highlighted intervals range from 1.1 metres to 7.2 metres, with grades of 590 ppm to 1,755 ppm Total Rare Earth Oxide (TREO). One highlighted result returned 7.2 metres at 1,751 ppm TREO from 14 metres depth. A second hole intersected 5.2 metres at 1,674 ppm TREO from 26.4 metres depth, and a third returned 1.7 metres at 1,755 ppm TREO from the same depth. Two further holes returned shorter intervals: one at 1.5 metres at 891 ppm TREO from 31.3 metres depth, one with 1.1 metres at 1,004 ppm TREO from 32.6 metres, and a second interval of 2.2 metres at 590 ppm TREO from 42 metres. Across all 14 holes, the grade range is consistent with the ionic rare-earth model's grade inputs, supporting their application within the MRE.

4. Permeability & Aquifer Geometry

In a confined ISR system, permeability governs how efficiently the lixiviant permeates the target horizon and is a primary determinant of wellfield spacing and extraction cycle duration.

Visual core logging from one of the initial resource-definition holes identified a 3.0-metre permeable horizon at 14.7 metres depth, grading 2,558 ppm TREO.

Particle-size distribution analysis is being performed on samples to calculate permeability.

5. Metallurgy: Acid Consumption & Recovery

The metallurgical envelope at Boland is defined by bench-test acid consumption across a range of pH levels and by Heavy Rare Earth Oxide (HREO) recovery rates from scaled bench studies.

Bench tests demonstrate acid consumption of 6.7 kg per tonne at pH 3, 1.95 kg per tonne at pH 4.5, and 1.6 kg per tonne at pH 5. A scaled bench study using 3.88 kg per tonne of acid achieved 66% recovery of HREO in 17 days. Sequential leach testing returned recoveries of 20 to 25% at pH 7, while benchtop metallurgy reached 44% recovery at pH 5 and 80% at pH 3.

6. Natural Acid Generation: On-Site Supply & Cost Impact

Sulphuric acid is a primary cost input in rare-earth element extraction, and global supply is currently constrained by conflict in the Middle East.

Organic pyrite within the Pidinga and Garford formations generates sulphuric acid in situ during the ISR process, reducing the volume of externally sourced acid required. Drilling at the Head prospect intersected 5.6 metres of heavily reduced Pidinga formation containing lignite interbeds from 25.9 metres depth, which appears highly favourable for ISR.

Samples are undergoing Total Organic Carbon and total sulphide analyses to quantify the on-site acid that the project can generate, allowing the company to model and demonstrate materially lower acid requirements.

7. Mixed Rare Earth Carbonate Composition & Product Quality

The optimised flowsheet produces a Mixed Rare Earth Carbonate (MREC) characterised by a high proportion of heavy rare earths, which management considers among the highest produced globally.

The flowsheet involves five steps across four pH stages: ISR at pH 3; cerium and iron removal at pH 4.5; aluminium removal at pH 6.2; uranium removal via resin exchange at pH 6.2; and MREC precipitation at pH 7.5. Cerium removal at pH 4.5 is achieved cost-effectively and eliminates the most abundant rare-earth element before final product precipitation. The resulting MREC composition is 43% HREOs, 34.2% neodymium and praseodymium, 4.5% dysprosium and terbium, and less than 0.9% impurities.

Managing Director of Cobra Resources, Rupert Verco, is direct about what the flowsheet composition means for the product's commercial position:

"Last week, we announced results for our optimized flowsheet that's produced one of the highest proportions of heavy rare earth mixed rare earth carbonates globally. That adds great strategic and commercial value, and it also provides great marketability. We've managed to remove all the cerium very cost-effectively. We have 4 and a half percent dysprosium and terbium and 43% heavies in that MREC, and we're producing it from one of the lowest cost forms of mining."

8. MRE Programme Status & Path to Economic Evaluation

Completion of the 74-hole resource-definition programme positions the company to advance toward formal economic evaluation.

The approximately 3,200-metre programme across the Boland and Head prospects is complete. Independent technical consultants have been engaged to support both the MRE and the subsequent Scoping Study. The target for the maiden collective resource is 200 to 400 million tonnes with TREO greater than 1,000 ppm.

Verco previewed, ahead of drilling, what completing the programme would make possible for economic evaluation:

"We're about to have two rigs out there going full ball on demonstrating the resource as soon as next week. What that's going to do for us is close out the work that we're going to need to do for economic evaluation at the Boland and Head rare-earth projects, and that's really going to then enable us to focus on the economic analysis for the rare-earth whilst we advance on the ground, the exploration potential at Manna Hill."

Key Takeaway for Investors

• Boland uses a confined In-Situ Recovery method rather than excavation or heap leaching, meaning economics are not determined by grade tonnage alone but by four variables, grade, permeability, metallurgy, and natural acid generation, that jointly govern operating cost and wellfield performance.
• The 74-hole resource-definition programme across the Boland and Head prospects is structured to capture data on all four variables simultaneously, so each can be formally modelled within the Mineral Resource Estimate and the subsequent Scoping Study.
• Preliminary results from 14 Boland drillholes provide encouraging observations for Total Rare Earth Oxide grades consistent with the project model's ionic rare-earth assumptions, and a 3.0-metre permeable horizon grading 2,558 ppm Total Rare Earth Oxides was intersected.
• Bench tests establish acid consumption of 1.6 to 6.7 kg per tonne across pH 3 to 5, and Heavy Rare Earth Oxide recovery of 66% in 17 days, while organic pyrite confirmed within the Pidinga and Garford formations enables on-site sulphuric acid generation, reducing external procurement requirements at a time when global supply is constrained.
• The optimised flowsheet produces a Mixed Rare Earth Carbonate with 43% Heavy Rare Earth Oxides, 4.5% dysprosium and terbium, 34.2% neodymium and praseodymium, and less than 0.9% impurities, with cerium removed cost-effectively at pH 4.5.
• Completion of the resource-definition drilling programme and engagement of independent technical consultants positions the company to advance toward a maiden collective Mineral Resource Estimate targeting 200 to 400 million tonnes at greater than 1,000 ppm Total Rare Earth Oxides, with economic evaluation and a Scoping Study to follow.

Bottom Line

Boland's economic case rests on four interacting variables, and the May 2026 initial assays provide encouraging observations for the model's assumptions. Grade intervals from those 14 drill holes are consistent with the ionic rare-earth concentrations assumed by the project model. Whether those conditions are consistent across the full 74-hole footprint will be determined by the remaining assays, particle-sizing analysis, and Total Organic Carbon results, now in progress.