Rainbow has two major rare earths opportunities: the Phalaborwa Project in South Africa and the earlier stage Uberaba Project in Brazil. Both projects entail the recovery of rare earths from phosphogypsum stacks that occur as the by-product of phosphoric acid production, with the original source rock for both deposits being a hardrock carbonatite.

Rainbow will use a proprietary separation technique developed by and in conjunction with its partner K-Technologies, Inc., which uses continuous ion exchange and continuous ion chromatography to simplify the process of producing separated rare earth oxides (versus traditional solvent extraction), leading to cost benefits, as well as being more environmentally friendly.

Rainbow also has a majority interest in the high-grade Gakara Project in Burundi, East Africa, which is currently on care and maintenance.

Rainbow is working together with OCP S.A. and Mohammed VI Polytechnic University to explore and develop the optimal technique for the extraction of rare earth elements from sedimentary-sourced phosphogypsum.