Mount Ridley Mines Confirms Rare Earths Hosted in Discrete Phospates at Grass Patch Complex

Results from Mount Ridley Mines’ (ASX: MRD) first automated mineralogy study on material from its Grass Patch Complex in Western Australia have shown that rare earth elements (REE) are hosted in phosphate minerals and support flotation as the primary beneficiation technique.

The study employed the TESCAN integrated mineral analyser (TIMA) automated scanning electron microscopy platform to identify the presence of discrete minerals xenotime, crandallite group phosphates, and monazite/rhabdophane.

Of these, xenotime is the most common and a strong potential host for valuable heavy rare earths.

The phosphates were found within a sample comprised mostly of clay, with smaller amounts of pyrite and quartz.

Critical Strategic Distinction

Unlike bulk chemical assay which reports the total concentration of an element without describing how it occurs, TIMA identifies the specific minerals hosting the element, their grain size, and how those minerals are physically associated within the surrounding material.

Mount Ridley considers the distinction critical to its processing strategy for a regolith-hosted deposit such as Grass Patch.

“Ionic clay deposits are typically defined by REE loosely adsorbed onto clay particle surfaces, amenable to simple salt leaching,” the company said.

“A deposit where REEs occur as discrete phosphate minerals opens a different set of processing options, including the potential to physically concentrate those minerals ahead of leaching.”

“Determining which mechanism applies and to what degree, directly informs the flowsheet we continue to develop through the test work program.”

Flotation Option Potential

The results also support the investigation of flotation as the primary beneficiation technique to concentrate the rare earths into a smaller, higher-grade product ahead of leaching.

This could potentially cut the volume of material fed into an ongoing Phase 1 metallurgical program, although further testing would be needed to confirm how well this works in practice.

Phase 1 test work commenced in May on representative mineralised clay samples from the Winstons and Keiths prospects within Grass Patch to establish a characterisation and beneficiation baseline and optimise feed ahead of hydrometallurgical processing.

The program is being led by Mount Ridley technical advisor Chris Larder, who has significant experience in the development and optimisation of processing flowsheets for WA rare earth and gallium-bearing systems.

Results will be integrated into Mount Ridley’s international metallurgical development initiatives as it advances the Grass Patch processing strategy and institutional research partnerships.