Rainbow Rare Earths (LSE:RBW), the rare earths developer, has begun a Pre-Feasibility Study (PFS) for its Uberaba project in Brazil under a joint development agreement with the Mosaic Company.
The move follows a March economic assessment that confirmed Uberaba as Rainbow's second major development opportunity, alongside its flagship Phalaborwa project in South Africa.
SRK Consulting has been appointed to prepare a maiden JORC-compliant Mineral Resource Estimate, the first of several technical consultants expected to be engaged for the study.
Uberaba sits in Brazil's Minas Gerais state, where Mosaic mines phosphate rock and produces phosphoric acid for fertiliser.
The PFS will assess a plant processing phosphogypsum waste at roughly 2.7 million tonnes a year over an initial 30-year mine life, with an originally modelled head grade of about 5,100 parts per million total rare earth oxides.
Mosaic is shipping a further six tonnes of phosphogypsum feedstock to Rainbow's laboratory and pilot plant in South Africa, building on flowsheet work adapted from the Phalaborwa project.
The March economic assessment put Uberaba's post-tax net present value at $916 million at a 10% discount rate, with a 45% internal rate of return, average annual EBITDA of $217 million and a payback period of 1.7 years, based on spot rare earth pricing from Argus Media at that time.
"Uberaba is expected to demonstrate the value of Rainbow's proprietary IP across other phosphogypsum projects," said George Bennett, chief executive of Rainbow, citing Brazil's role in rare earths supply chain independence and US government support for the sector.
The PFS is expected to complete in the second half of 2027.
News Intelligence what this means for the company
Rainbow has formally commenced a Pre-Feasibility Study on Uberaba, its second major rare earths project in Brazil, with SRK Consulting appointed to deliver a maiden resource estimate. This advances the project from a March economic assessment (which modelled $916 million post-tax NPV and 45% IRR) into engineering and technical validation, de-risking the pathway to a development decision by late 2027—a critical step for a company with two projects at different maturity stages and backing from US government-linked investors.
- Mosaic's continued feedstock supply and co-development role anchors Uberaba's economics to an established phosphate operator with existing infrastructure in Minas Gerais, reducing execution risk on the waste-processing model.
- The staggered timeline (Phalaborwa DFS targeted 2026, Uberaba PFS completion H2 2027) creates a sequenced capital and management intensity that will test Rainbow's ability to fund and execute two projects in parallel.
Uberaba's progression from concept to formal study validates Rainbow's phosphogypsum-to-rare-earths model at a second site and strengthens the case for a US listing (under review) by demonstrating scalable, government-backed supply-chain value. However, the 18-month study timeline and dependence on Mosaic's feedstock quality and commitment remain execution risks before any capital commitment.
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