Dense Media Separation (DMS) test work undertaken by Latin Resources Ltd (ASX:LRS, OTC:LRSRF) on ore from the Colina deposit ore at the 100%-owned Salinas Lithium Project in Brazil, has confirmed the company’s ability to produce a high-grade, low-impurity spodumene concentrate.
The test work yielded an impressive 93.1% stage recovery to a high-quality spodumene concentrate grading 5.5% Li2O.
The results of the test work will be invaluable for the company’s upcoming preliminary economic assessment (PEA) and definitive feasibility study (DFS).
‘Quick to market’ potential
Importantly, the successful operation of the DMS pilot plant demonstrates the potential for LRS to build a simple first-stage ‘quick to market’ DMS circuit.
“These latest metallurgical test results very clearly demonstrate the amenability of the Colina spodumene pegmatite to simple DMS processing, validating assumptions drawn from the initial benchtop scale HLS test work,” Latin Resources’ vice president of Operations - Americas Tony Greenaway said.
DMS processing is commonly used in the spodumene lithium sector and has been shown to have significant cost-saving implications for both capital and operating costs.
As Greenaway notes, Latin is in the final stages of completing a PEA based on the Colina Lithium Deposit, which will include estimates of both capital and operating costs for the project.
This current PEA work comes ahead of a much larger one planned for Q4.
“A much larger DMS and other test work program will be undertaken in Q4 of this year utilising more than 2,000 kilograms of spodumene pegmatite samples from Colina,” Greenaway said.
“The aim of this work is to build on these initial very encouraging results and fine-tune the processing flowsheet for the Colina DFS.
“This work may include additional downstream processing as well as initial investigative work on lithium recovery from fines generated during normal run of mine operating conditions.”
The testing in detail
Latin enlisted Canada's SGS Lakefield laboratories for a comprehensive metallurgical test on ore from its 45.2 million tonnes Colina deposit. An independent review was provided by MinSol Engineering Pty Ltd, a firm known for its deep experience in lithium processing, metallurgy and plant design.
Dense Media Separation (DMS) Pilot Plant at SGS’ Lakefield, used for the Colina DMS test work.
The objective of the testing was to evaluate the efficiency of DMS – a widely recognised industry process – in refining spodumene from its impurities using a gravity-separation technique. In addition, Heavy Liquid Separation (HLS) was simultaneously conducted on composite samples to give a holistic view of DMS performance on a larger scale.
In its initial bulk DMS tests, Latin announced the production of a premium concentrate with a grading of 5.5% Li2O and a remarkable 93.1% stage recovery from a sample that had a base grade of 1.38% Li2O.
Given the breadth of the testing, these results are deemed a reliable predictor of commercial DMS outcomes.
Latin anticipates stage recoveries exceeding 90% to a 5.5% Li2O concentrate, which promises to enhance the forthcoming PEA's economic outlook.
Furthermore, a coarse DMS product, which is not only more straightforward and cost-efficient to produce but also preferred for conversion into lithium chemicals like lithium hydroxide due to its reduced fines, is expected to pique the interest of potential end-users.
About DMS
DMS, a commercial-scale separation process, leverages traditional principles of density separation. In this method, a mixture of ore and dense medium, typically consisting of FeSi or magnetite slurry, is funnelled through a hydrocyclone. This process divides the slurry into two distinct products - a denser underflow (sinks) and a less dense overflow (floats).
For the bulk DMS test, SGS prepared approximately 137 kilograms of HQ-sized core samples from 35 drill holes, with samples derived from both mineralised and non-mineralised zones within the Colina deposit. This aggregate sample had a grade of 1.31% Li2O.
The sample was then processed to generate a -6.3mm +1.0mm DMS feed with a grade of 1.38% Li2O. Notably, any fraction below -1.0mm was reserved for subsequent testing. From this DMS feed fraction, a portion was designated for HLS, with the remaining 99kg undergoing DMS processing.
The equipment chosen for this bulk testing phase incorporated a standard DMS circuit, highlighted by a 200mm diameter Multotec separation cyclone. For perspective, the full-scale production facility is projected to deploy 420mm separation cyclones.
Given the well-documented performance characteristics of the 200mm and 420mm cyclones, the efficiency of separation observed in this test can be compared directly to the output of a full-scale production setup.
During the testing phase, the 99kg sample underwent two testing campaigns at different specific gravity (SG) cut points. After the completion of Test 1, its products were repurposed as inputs for Test 2.
Detailed results from the DMS testing phase.
The outcomes from the DMS test showed a consistent alignment with the HLS grade/recovery curve, pointing to an optimal mineral composition for this processing approach.
Specifically, a DMS concentrate with a 5.5% Li2O grade was achieved at 93.1% stage recovery, while the HLS recovery stood at 95.4%, marking a mere 2.3% absolute variance.
Comparison of DMS Test 1 and 2 with HLS Grade/Recovery Curve.
Given this data, the HLS findings are viewed as a dependable metric for evaluating commercial DMS efficiency. It is projected that stage recoveries surpassing 90% to a 5.5% Li2O DMS concentrate are feasible. In essence, the Colina ore can yield a high-grade concentrate through a DMS-only approach, backed by impressive overall recoveries.
What’s next?
Recent test work data affirms Latin's assessment that employing a DMS flowsheet will be the optimal and most economical approach for processing the Colina deposit ore.
The company will now embark on additional studies to identify the best process for the fine fraction not addressed by DMS.
Insights derived from this metallurgical testing phase will be integrated into the forthcoming PEA, slated for publication in Q3 of 2023.
Moreover, Latin is planning on conducting further bulk sampling in the ensuing months, aimed at supporting a more comprehensive examination of the Colina deposit ore – a crucial step as it prepares for the DFS expected to be unveiled in the first half of 2024.