Jindalee Lithium (ASX:JLL) produces high purity MgO from McDermitt testwork
Jindalee Lithium has successfully produced high grade magnesium oxide (MgO or Magnesia) from ore from the McDermitt Lithium Project in the United States, with the results establishing an initial proof of concept in the company’s magnesium value optimisation program.
The testwork assessed the conversion of magnesium sulphate (MgSO₄) brine produced from McDermitt ore into MgO.
Highlights
Testwork converted MgSO₄ from McDermitt ore into high purity MgO with 93.4% equivalent MgO content.
Both testwork approaches produced MgO grades greater than 93%, with calciner conversion values reaching 99.95%.
Results establish an initial proof of concept for a potential higher value magnesium by product at McDermitt.
Further testwork and studies will assess commercial viability, reagent recycling and potential by product economics.
Jindalee completed the McDermitt PFS in November 2024, which identified scope for process optimisation and potential magnesium by product recovery.
In October 2025, the company commenced a value optimisation program to assess options to recover and monetise magnesium streams previously assumed to be discarded in the PFS.
The latest testwork was undertaken by Kemetco Research Inc. and investigated producing MgO from MgSO₄ brine samples produced from McDermitt ore.
The program assessed two approaches, including adding carbonates to the brine to precipitate magnesium carbonate followed by calcination to produce MgO, and crystallising hydrated MgSO₄ from the brine followed by thermal conversion to anhydrous MgSO₄ ahead of reductive calcination to produce MgO.
Both approaches produced MgO grades greater than 93%, with the highest grade reaching 93.4% MgO and calciner conversion for both approaches reaching 99.95%.
The results provide a technical basis for Jindalee to assess whether magnesium previously treated as waste can instead be converted into potentially higher value magnesium products.
The company stated that further testwork, engineering and commercial assessment are required to establish product specifications, scalability and commercial viability at McDermitt.
Further market and engineering studies will assess the financial viability of producing magnesium by products, including operating cost impacts, capital efficiency, market demand and overall project economics.
Jindalee Managing Director and CEO Ian Rodger said the results were a significant technical step in assessing the magnesium opportunity at McDermitt, with further work focused on determining whether a magnesium by product will be incorporated into the upcoming McDermitt Feasibility Study.
“It is too early to draw concrete conclusions on commercial viability or Project economics, but our next phase will focus on completing the work necessary to decide whether a magnesium by-product will be incorporated into the upcoming McDermitt Feasibility Study.”
The magnesium assessment follows previous PFS stage testwork, which confirmed that magnesium can be efficiently extracted alongside lithium using sulphuric acid leaching, with extraction of up to 97.2% reported from representative mineralised units.
The PFS treated magnesium as waste, removing it from the process as magnesium sulphate with no revenue credit applied.
Jindalee’s next steps include completing further market and engineering studies to assess the financial viability of producing magnesium by products, undertaking additional testwork designed to improve on the initial results, and updating the Mineral Resource estimate to include magnesium.
Additional drilling is planned to upgrade the Mineral Resource estimate and obtain samples for large scale metallurgical testwork covering lithium and magnesium.