iTech undertook diagnostic metallurgy on 11+ year old samples from the Eyre Peninsula Kaolin-REE project to identify whether the mineralisation had a REE ionic adsorption clay component
The samples showed encouraging levels of ionically adsorbed rare earth elements and confirms that there is an ionic component to the REE mineralisation
This is despite the fact that the samples were:
of limited volume
composited across thick intervals of the weathering profile
exposed to the atmosphere for a considerable period
Results are comparable with early-stage test work from other leading ionic clay projects outside of China
Results give iTech the confidence to pursue a more detailed program of metallurgical test work
Samples from the 165 holes drilled at the Ethiopia, Burtons and Bartel Prospects will provide ideal samples for further test work
The aim of the initial phase of diagnostic test work was to determine if the process of ionic adsorption of REEs onto clays was a geological process present at the Company’s Eyre Peninsula Projects. The test work confirms that both the Ethiopia and Burtons Prospects have an ionic component to REE mineralisation. iTech considers the results to be diagnostic in nature (determine if ionic REEs are present) as the quality of the samples available for testing prior to the current drilling program was less than ideal.
Initial Metallurgical Evaluation iTech Minerals (ASX: ITM) undertook high-level test work on selected intervals of historical samples drilled approximately 15 years ago at Ethiopia in 2007 and 11 years ago at Burtons in 2011. The Ethiopia samples were recovered from the South Australian Core Library and the Burton samples were obtained from exploration samples acquired from Archer Materials earlier this year and sent to ANSTO (the Australian Nuclear and Science Technology Organisation) and reviewed by Damian Connelly at METS Engineering.
Given that the aim of the test work was diagnostic and on 11+ year old samples, a very simple leach process was employed to test the easily leachable ionic fraction under standard conditions.
0.5M (NH4)2SO4 as lixivant
Ambient temperature of 220C; and
2 wt% solids density
This process was designed to only target the easily leachable ionic component of REE mineralisation over a short exposure period. No additional leach steps, analysis of wash water or variation of pH, were undertaken which have the potential to increase levels of extraction.
Each of the leach tests was conducted on 40g of dry, pulverised sample and 1960g of the lixiviant in a 2 L titanium/ stainless steel baffled leach vessel equipped with an overhead stirrer. The results of the tests on selected clay samples were used to calculate average extractions for each composite sample. The testing demonstrated that:
Recoveries of the ionic component of REE mineralisation are between 24-26% from 4 drill holes at Ethiopia with very low acid addition
Recoveries of between 10-21% were obtained from 4 holes at Ethiopia with very low acid addition and 4 holes at Burton with very low to moderate acid addition
Recoveries of <10% were obtained from 2 holes at Ethiopia and 6 holes at Burtons with very low to moderate acid addition
The test work was successful in identifying that a component of the mineralisation is ionic in nature and that the process to form IAC REE deposits is present on the Eyre Peninsula tenements. Due to the historic nature of the samples, extrapolation to expected recoveries from the broader mineralisation is limited, due to:
The unknown effect of the samples being exposed to the atmosphere over the last 11-15 years. The ionic mineralisation is controlled by several factors including pH of the environment. Prolonged exposure and oxidation could cause significant changes to the chemical and physical conditions and the nature of REE mineralisation.
The limited sample size preserved from sampling and intervals required to be composited to achieve enough sample for testing
The lack of definition of the location of the sample in the weathering profile as the ionic component of mineralisation is generally associated with a specific horizon
Notwithstanding these limitations, iTech is very encouraged by the results and is now confident in undertaking an optimised metallurgical assessment on the recently drilled kaolin-REE prospects at Ethiopia, Burtons and Bartels.
Having recently drilled all three of these prospects, the company now has appropriate samples to fully assess recoveries of REEs. The drilling has provided samples which:
· Is fresh “out-of-the-ground” and hasn’t been exposed to prolonged atmospheric oxidising conditions which could alter the ionic nature of mineralisation
· Provides sufficient sample size to undertake multiple leach tests under varying conditions including lower pH which has the potential to mobilise any colloidal REEs
· Can be located within the weathering profile and samples selected from the most prospective horizon in which ionically adsorbed REEs are known to occur
Example of high purity kaolin intersected in drilling at the Ethiopia Kaolin-REE Prospect
Discussions have been held with ANSTO to determine the best sample size, location and leaching conditions to undertake a comprehensive program of metallurgical optimisation. Options include varying a range of conditions including varying pH and leach times, multiple leach stages and the additional washing steps.
Samples from the recent drilling program at Ethiopia, Burtons and Bartels are currently with geochemical laboratories for analysis. Once results have been received by iTech, the company will select representative sample from all three prospects to undergo a program of metallurgical optimisation. Samples will be selected to broadly assess metallurgical performance of mineralisation from differing geological characteristics such as regolith zones and varying depths from surface.
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