“The 51.8% TREO mixed rare earth carbonate result exceeded my expectation, and the high proportion of magnet rare earths of more than 31% attests to its potential for premium commercial value. Nonetheless we still have work to do to reduce impurities to levels that are necessary to demonstrate product marketability.
“Taken together with the positive metallurgical variability testwork results reported in March, we are sufficiently encouraged by today’s result to upscale our downstream program to produce an increased volume of mixed rare earth carbonate for market assessment. Collection of feed material for this program is underway.”
In previous phases of the metallurgical program, simple screening of 13 (mainly 5-metre) mineralised composites from 10 drill holes by Perth-based Strategic Metallurgy (“Strategic”) demonstrated a 2x rare earth upgrade to -25µm undersize representing 37.2% of the bulk saprolite feed mass (refer to ASX announcement 13 December 2022). Subsequent acid leaching of the undersize by Strategic extracted an average of 82.9% of the magnet rare earths, consuming 18.1 kg of 32% hydrochloric acid per tonne of undersize feed for preferred material types (refer to ASX announcement 12 July 2023).
These results allowed HRE to develop whole rock geochemical algorithms to select an additional 63 (mainly 6-metre) mineralised composites from 55 drill holes across the entire project area for an expanded program of sizing and diagnostic leach testing. This program delivered results consistent with earlier phases of the program and demonstrated relatively modest metallurgical variability across the Cowalinya resource with preferred material types, characterised by high leachability (>75%) of the payable magnet rare earths Pr, Nd, Tb and Dy and low consumption (<40 kilograms per tonne of undersize feed) of 32% hydrochloric acid, potentially occupying a sizeable extent of the currently defined resource (refer to ASX announcement 12 March 2024).
Separately, Strategic prepared a 1 kg blend of screened undersize leach feed from 4 of the 13 mineralised composites used in the original sizing and acid leaching sighter work, for the development of a conceptual downstream flowsheet to produce MREC. The sample blend had a TREO grade of 2,595 ppm and was subjected to a simple leach, purification and precipitation regime as shown in Figure 1.
Without any optimisation, a high grade (51.8% TREO) MREC was produced containing a high proportion of the valuable magnet rare earths Pr, Nd, Tb and Dy representing 31.2% of the total rare earth content. A detailed analysis of the rare earth content in the leach feed and MREC solids is presented in Table 1.
Whilst the total impurity content at 8.4% (mainly iron, copper and sodium) is over specification for a commercial rare earth separation plant (typically below 5%), the Company emphasises that this was a ‘first pass’ concept program to demonstrate that MREC can be produced from the Cowalinya deposit.
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