Canada-listed rare earths explorer Mkango Resources has announced a significant increase in leach recoveries in the metallurgical optimisation testwork conducted as part of the ongoing prefeasibility study for the Songwe Hill rare earths project, in southern Malawi.

Mkango president Alexander Lemon says the metallurgical process has recovered significant quantities of a range of rare-earth elements, including lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium and yttrium.

He says: “The concentrate was produced through flotation of a representative composite sample of drill core from the project. The results indicate that recoveries may be significantly enhanced by including a caustic conversion step in the flowsheet.

“Other metallurgical optimisation is ongoing, including the incorporation of a gangue preleach step to provide a clean solution for hydrochloric acid recycling, along with improvements to the flotation stage. With respect to the latter, recent testwork has demonstrated an increase in heavy rare earths recoveries to a level similar to light rare earths recoveries.”

Mkango CEO William Dawes is optimistic about the project. He says: “The increased leach recoveries could potentially have a significant impact on project economics – in particular, an increase in recoveries for neodymium, praseodymium, europium and dysprosium, which account for a large proportion of the in situ value for Songwe Hill.”

He explains that Songwe Hill's favourable mineralogy, comprising synchysite and apatite that is anomalously enriched in heavy rare earths, means that capital- and energy- intensive kilns will not be required, in contrast to projects dominated by monazite, xenotime or other refractory rare-earth elements.

Dawes says plant design will comprise conventional technology, largely comprising tanks, pumps and filters, and will be modular, allowing for future expansion.

“The use of low-strength acid will enable the use of plastics or composite materials for tanks and pipework, and will facilitate acid recycling using cheaper sulphuric acid,” says Dawes.

The Songwe Hill rare earths deposit, located in Malawi’s southern district of Phalombe, features carbonatite-hosted rare-earth mineralisation.

Mkango, which is listed on the TSX Venture Exchange, is also undertaking regional exploration in its second licence area, known as Thambani, where potential for uranium, zircon, corundum and niobium have been identified.