Mount Ridley Study Backs Flotation Theory at Grass Patch

Mount Ridley study confirms that rare earth elements at the Grass Patch deposit are primarily hosted within three phosphate minerals, opening a possible flotation route for concentrating the ore before leaching.

Mineralogy findings reveal phosphate hosts

The mineralogy analysis, carried out on samples from the Grass Patch Complex near Esperance, Western Australia, shows that xenotime, members of the crandallite group and monazite‑rhabdophane together hold almost all of the rare earth elements (REEs) present. Using the ESCAN Integrated Mineral Analyzer (TIMA), researchers mapped the distribution of these minerals at a microscopic level, noting that they are fine‑grained and closely interwoven with surrounding clay. This texture matches the shallow, weathered regolith profile that characterises the deposit.

According to the report, the phosphate minerals sit within the free‑dig, shallow profile that makes the Grass Patch ore amenable to conventional mining methods. The study also recorded grain‑size data, confirming that the REE‑bearing phosphates are typically less than a few microns across, a factor that influences downstream processing choices.

Potential flotation pathway

The findings suggest that flotation could be used to concentrate the REEs into a higher‑grade product before the leaching stage. Mount Ridley Mines (ASX:MRD) plans to undertake bench‑scale flotation trials across a range of grind sizes to determine achievable concentrate grades and recovery rates. The company expects these tests to complement the Phase 1 metallurgical work, which is nearing completion.

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“The TIMA results inform us exactly how the rare earths sit in our deposit,” managing director Allister Caird said. “Some of our peers have had outstanding results applying flotation to comparable regolith‑hosted HREE deposits and these results provide a basis for MRD to investigate a similar beneficiation pathway.” He added that the firm is “excited about the prospect of flotation to concentrate our ore” and will update shareholders once the Phase 1 results are released.

While the flotation concept remains under investigation, the mineralogical evidence gives a clear direction for the next stage of processing development. If successful, the approach could reduce the volume of material that proceeds to leaching, potentially lowering costs and environmental impact.

The next phase is upcoming.

From a broader standpoint, the ability to separate REEs early in the process aligns with industry trends toward more efficient, lower‑footprint extraction methods. Many rare earth projects struggle with high water usage and large tailings piles; a flotation step that narrows the material stream could mitigate those challenges. However, the actual performance will depend on how the fine‑grained phosphates behave in a scaled‑up circuit, something the upcoming bench tests aim to clarify.

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The ESCAN TIMA platform, an automated scanning electron microscope system, has become a standard tool for mineral‑focused investigations across mining companies. By providing detailed images and compositional data, it enables projects like Grass Patch to pinpoint the exact mineral hosts of valuable elements, informing both mine planning and processing design.

In addition to the phosphate hosts, the study noted that the REE‑bearing minerals are intimately associated with the surrounding clay matrix. This close association may affect flotation recovery, as fine particles can be difficult to separate without appropriate reagents or conditioning. The upcoming laboratory work will explore reagent blends and conditioning times to address these issues.

Overall, the mineralogy study does not guarantee that flotation will deliver the desired concentrate grades, but it does lay a factual foundation for further experimental work. The company’s next steps include conducting bench‑scale tests, analyzing the results, and integrating any successful findings into the broader metallurgical strategy. Shareholders can expect a detailed update once the Phase 1 metallurgical program concludes, which is slated for the near term.