ABx Group Limited (ASX: ABX) has received excellent 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 sulphate 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.
Results from Deep Leads and Rubble Mound projects are both excellent
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.
It is significant that these results were obtained using ammonium sulphate 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.
It is extremely pleasing to confirm that there is widespread ionic adsorption clay rare earths at Deep Leads and Rubble Mound,” CEO and Managing Director, Mark Cooksey, said.
“ABx is expediting both its drilling programme and its process development program, with the objective of bringing this project into production as soon as possible. New supply is essential to meet the rapidly increasing global demand for rare earths.”
Drilling Programme
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.