ABx Group Limited has received results from its representative batch of 71 desorption tests on rare earth element (REE) samples from its Deep Leads and Rubble Mound deposits in northern Tasmania. The desorption tests were conducted by ANSTO at Lucas Heights in Sydney, which has extensive experience in metallurgical testing of clay-hosted rare earth deposits worldwide. Tests were conducted at `standard' desorption conditions of 0.5 M ammonium sulfate at pH 4, which are low-acid, low-cost processing conditions for ionic adsorption clay REE (IAC REE).

Highest reported extractions from clay-hosted REE prospect in Australia: The extractions of contained REE ranged from 24% to 83% for the 44 samples from the extensive IAC REE zones in the Maiden Resource estimate announced on 23 November 2022. 73% of the samples from the more closely-drilled Deep Leads project area had minimum 24% extraction and average 50% extraction. These confirm that Deep Leads is an ionic adsorption clay REE deposit.

Samples from IAC REE zones of Rubble Mound performed similarly to the samples from IAC REE zones of Deep Leads. Current drilling is focussed on extending these IAC REE zones. ABx tested representative samples from Deep Leads and Rubble Mound.

The results increased ABx's understanding of variations in REE extraction and, most importantly, confirmed that both Deep Leads and Rubble Mound have large zones of genuine ionic adsorption clay REE mineralisation. Some zones have exceptionally high extraction, including 83% extraction for one sample from Rubble Mound, which is only in the early stages of drill evaluation. Deep Leads has been drilled more extensively, and 36 of the 49 samples (73% of samples) achieved extractions above 24%, averaging 50% overall.

Large potential extensions to the IAC REE zones have been identified by this testwork at both Deep Leads and Rubble Mound, and the drill rig that is currently exploring at Deep Leads and Rubble Mound has been deployed to drill out these newly identified IAC REE zones. High extractions were achieved from drillholes that were geographically widespread across Deep Leads and Rubble Mound, and came from drill samples taken from a range of depths. High extractions were obtained from the full range of REE grades and were not restricted to the higher grade samples.

An advantage of this IAC REE type of mineralisation is that it is proportionally enriched in the four most valuable REE that are used in permanent magnets, namely praseodymium (Pr), neodymium (Nd), terbium (Tb) and dysprosium (Dy). Furthermore, the extractions achieved from these desorption tests are highest for these permanent magnet REE (Table 1). It is significant that these results were obtained using ammonium sulfate at pH 4, which is similar to the conditions used in China for purely ionic adsorption clay type deposits.

Many clay-hosted REE deposits can require lower pH to achieve similar levels of REE extraction. The widespread high extractions mean that ABx can give more consideration to processing of ionic adsorption clay REE deposits, namely mining, desorption, impurity removal and precipitation. Optimised processes are crucial to maximising the profitability of a rare earth project.

ABx has already engaged with ANSTO on the desorption tests described here, and is developing relationships with other organizations with expertise in rare earths. The results also enable early development of rehabilitation technologies that suit the Tasmanian setting of the ABx deposits within hardwood plantations that may be replanted after REE production. ABx has been conducting further drilling of the Deep Leads and Rubble Mound deposits since 17 January this year and is expediting assay results.

Drilling of the outlying greenfield areas during the second half of 2022 was highly successful. It was conducted subject to a Tasmanian State Government, Exploration Drilling Grant Initiative (EDGI) for co-funded exploration drilling projects, which is gratefully acknowledged.