Mount Ridley Mines (ASX:MRD) Selectro™ testwork reports HREE, scandium and gallium recoveries
Mount Ridley Mines has reported initial results from its ongoing metallurgical testwork program conducted on historical drill samples from the Grass Patch Complex in Western Australia.
The results demonstrate the ability of its wholly owned Selectro™ Process to recover HREE, LREE, scandium and gallium from unbeneficiated Grass Patch material through a single proprietary leach process, with comparative hydrochloric acid, HCl, testing undertaken on the same composite sample.
Highlights
HREE recoveries of 77% to 83% were achieved across dysprosium, terbium, yttrium, erbium, europium, gadolinium and holmium.
LREE recoveries were between 70% and 77% across neodymium, praseodymium, lanthanum, cerium and samarium.
Scandium recovery reached 80%, while gallium recovery averaged 56%.
The material was tested without prior beneficiation and the results represent initial laboratory testwork ahead of further optimisation.
The results relate to a single composite sourced from 5 diamond drill intervals and are not represented as demonstrating metallurgical performance across the entirety of Grass Patch.
The material was unbeneficiated and the Selectro™ testwork represents initial, non systematically optimised laboratory testing.
The metallurgical program was conducted by Nagrom Pty Ltd, an independent metallurgical laboratory in Perth, Western Australia.
It comprised comparative HCl baseline testing and 2 Selectro™ leach tests using representative dry weight aliquots of approximately 90 g derived from a 16.8 kg homogenised composite prepared from 5 historical Grass Patch diamond drill holes.
The HCl baseline and Selectro™ tests were each conducted over a 24 hour leach period, with the Selectro™ results achieving maximum recoveries in under 4 hours, and all leach tests were conducted at atmospheric pressure.
Selectro™ Test 2 achieved recoveries of 83.1% for terbium, 80.2% for yttrium, 77.6% for erbium, 77.5% for gadolinium, 77.4% for holmium and 77.3% for dysprosium.
Neodymium recovery was 75.2%, praseodymium 73.6%, samarium 72.7%, lanthanum 71.3% and cerium 69.9%.
Scandium recorded 80.0% recovery in Test 2 compared with 27.6% under the HCl baseline, while gallium recorded 55.8% in Test 2 compared with 0.0% under the HCl baseline.
The Grass Patch Complex hosts a JORC 2012 Inferred scandium resource of 367.98Mt at 57.3ppm Sc and a JORC 2012 Inferred gallium resource of 838.7Mt at 29.3ppm Ga.
The Rare Earth Oxide Global JORC 2012 Resource Estimation stands at 122.5Mt at 889ppm TREO for 108,954t contained TREO metal, including 44,610t contained HREO, reported at a 300ppm TREO cut off, while the central Mia Prospect has a Global JORC 2012 Inferred Resource Estimation of 168Mt at 1,201ppm TREO.
The mineralisation has previously been described as a shallow regolith hosted rare earth system at Grass Patch.
A TIMA study announced on 6 August 2026 confirmed that rare earths in the tested composite are predominantly hosted in discrete phosphate minerals, including xenotime, crandallite group phosphates and monazite/rhabdophane, with the current metallurgical testwork evaluating the leach response of material from this composite.
Mount Ridley Chief Technology Officer Chris Larder said:
“The Selectro™ Process is the culmination of over a decade of development and refinement, so it is very encouraging to see the technology deliver strong results on Mount Ridley material. These results provide further confidence in the process and support its progression into the next phase of optimisation and larger-scale testwork.”
The Selectro™ Process is the company’s proprietary hydrometallurgical technology developed to recover multiple critical minerals through a single leach process.
Mount Ridley states that the process incorporates reagent recycling through a closed loop processing system and is being developed to enable the recovery of rare earth elements, scandium and gallium from a common feed stream.
The company is also assessing pathways to commercialise the technology as the foundation of its own project development and as a potential licensed technology for application by 3rd parties globally.
The Selectro™ Process will now be tested on a bulk sample from the Grass Patch Project, with the bulk sample program also testing the process on beneficiated feed by applying flotation to a portion of the sample before leaching, while Mount Ridley intends to validate the process on 3rd party feed.
Further metallurgical programs are focused on beneficiation, process optimisation, reagent recycling and downstream product development.