London-based Rainbow Rare Earths has increased the mineral resource estimate (MRE) of its Phalaborwa rare earths project, in Limpopo, to a measured and indicated 30.4-million tonnes at 0.44% total rare earth oxide (TREO), with the high-value, permanent magnet elements neodymium and praseodymium representing 29% of the TREO in the rare earths basket.

The updated MRE, reported at a 0.2% TREO cut-off grade, also hosts economic quantities of dysprosium and terbium.

“Today’s resource upgrade is the result of infill drilling which has confirmed our expectations that the project’s two phosphogypsum stacks are homogenous and consistent in grade,” says Rainbow CEO George Bennett.

As part of the definitive feasibility study (DFS), Rainbow will undertake additional drilling to upgrade the MRE further, expecting that more accurate density measurements below the water table of the gypsum stacks at Phalaborwa will provide an opportunity to increase the total tonnage contained in the resource.

As such, the company notes that the project remains on track to reach production in 2026 – five years after initial work started on site in 2021.

Rainbow reports that key workstreams have started to advance its Phalaborwa project to the DFS stage – a key part of this being the implementation of a pilot plant operation, of which the design and setup are progressing in line with expectations.

Commissioning of the pilot plant will start in the second quarter, producing sufficient quantities of separated permanent magnet rare-earth oxides for testing and marketing purposes in offtake discussions with potential partners.

Bennett says successful operation of the pilot plant will give further confidence to the company’s plans to leverage its proprietary technology, with the aim of targeting opportunities to produce rare earths from historic phosphogypsum stacks, or as a by-product of phosphoric acid production, on a global scale.

The unique and innovative rare earths processing flowsheet designed for the Phalaborwa project will use continuous ion-exchange/continuous ion chromatography (CIX/CIC) technology to deliver separated magnet rare-earth oxides, which has been developed in collaboration with Rainbow’s partner K-Tech.

By separating the pilot process between two different centres of minerals processing performance, Rainbow expects to benefit from cost and time efficiencies as a result of removing the logistics involved in transporting pilot-scale equipment from the US – where it is designed, fabricated, and tested – to South Africa, where it would have to be reassembled and commissioned.

It will be more efficient to transport the mixed rare earth sulphate intermediate solid material produced by the front end, which is a low-volume but high-value product that is readily transportable.

Rainbow also expects to benefit from key K-Tech personnel being present throughout the running of the pilot, with the ability to oversee and optimise the CIX/CIC process in real time.

In addition, Rainbow reports that work has started with mineral research organisation Mintek to design and fabricate the front end of the plant, which will produce a high-value mixed rare earth sulphate.

The required back-end separation process CIX/CIC units have been delivered to K-Technologies’ Lakeland facility for setup and testing.

Bennet adds that the potential for Rainbow to provide an environmentally responsible, near-term source of the magnet minerals critical for global decarbonisation has attracted interest from strategic global investors and discussions with funding partners are progressing well.