Western Australian explorer Desert Metals (ASX:DM1) has uncovered a potential processing route through initial metallurgical testwork at its Innouendy Rare Earth Project in Western Australia.
The company reports the preliminary testwork program saw a series of leach tests conducted on 2 composite samples from the Main Zone and Cattle Yard at different depths and rare earth element (REE) grades. Samples were selected to include both ‘higher grade’ samples and material, which the company says is typical of less mineralised clays.
The initial series of leach tests were conducted on the individual composite samples using sulphuric acid and ammonium sulphate at pH 3, 2, and 1 over 24 hours at room temperature. Desert reports recoveries of REE for these initial tests were ‘relatively low’, which indicates more ‘aggressive’ leaching conditions are required.
Meanwhile, the second series of leach tests were conducted at higher acid concentrations, with all tests conducted on a composite sample consisting of equal parts from all 5 Main Zone deposit samples.
Both hydrochloric and sulphuric acids were trialled in the leach tests, and for tests at pH1, ammonium sulphate or sodium chloride salts were added with either sulphuric or hydrochloric acids.
In tests with acid concentrations stronger than pH1, Desert says only acids were added. All tests were conducted at 40ºC at atmospheric pressure over 48 hours, and the solids concentration was maintained at 14% solids by weight.
Desert reports the preliminary tests demonstrate that recoveries above 70% of the ‘key’ economic REE can be achieved using relatively low acid additions at close-to-ambient temperatures and atmospheric pressures, while recoveries over 90% can be achieved by increasing acid additions.
However, the company says higher acid additions also result in higher acid consumption, as well as increased dissolution of non-valuable elements, resulting in increased downstream separation costs.
Desert reports the results suggest that leaching is ‘strongly’ impacted by kinetic factors such as temperature, time, and acid concentration and suggest the direction for future testwork.
Based on the testwork, the company says both hydrochloric and sulphuric acid are effective at leaching REE, while a selection of the ‘most economic’ acid will depend on the cost of supply and ease of recovering acid remaining in the solution after leaching.
Commenting on the metallurgical testwork results, Desert Metals Managing Director Rob Stuart says: “We are pleased that our initial metallurgical testwork results are in line with our West Australian clay-hosted REE peers and have successfully defined a potentially viable and relatively simple process route for these deposits.
“The currently constrained supply and strategic nature of the REEs bodes well for future price improvements”
The currently constrained supply and strategic nature of the REEs bodes well for future price improvements, which could make the Innouendy Project a valuable asset.”
Desert Metals is an ASX-listed explorer searching for intrusive nickel, copper, and rare earths on the northwest margin of the Yilgarn Craton in Western Australia. The company’s portfolio of assets includes the Innouendy and Irrida projects, which cover more than 1,600km-square of exploration tenements.
Write to Harry Mulholland at Mining.com.au
Images: Desert Metals Ltd
