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Rainbow Rare Earths announce Phalaborwa resource estimate

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Global Mining Review,

Rainbow Rare Earths Ltd has announced a maiden JORC (2012) compliant mineral resource estimate in respect of the Phalaborwa Project in South Africa.

  • Inferred mineral resource estimate of 38.3 million t at 0.43% total rare earth oxides (TREO) is larger than the original 35 million t expected from the gypsum stacks.
  • High value neodymium (Nd) and praseodymium (Pr) oxide, the essential metals for permanent magnets powering the green revolution, represent 29.1% of the total contained rare earth oxides, with an in-situ value of US$95/t gypsum.
  • Economic dysprosium (Dy) and terbium (Tb) oxide credits, with an in-situ value of US$28/t gypsum, enhance the overall value of the rare earth basket contained in the stacks, with the in-situ value of these four high value rare earth elements totalling US$123/t gypsum.
  • Very low levels of radioactive elements confirmed in the inferred mineral resource estimate confirm the 'green' credentials of this project.

George Bennett, CEO, said: “The maiden mineral resource estimate for Phalaborwa marks an important milestone for Rainbow, underpinning the opportunity for the rapid development of a low capital and operating cost, high value processing facility in South Africa to provide the essential metals to power the green revolution from an extremely environmentally beneficial project.

“The fact that the rare earths are present in a chemical rather than mineral form in the gypsum stacks removes the need, as with the majority of global rare earth projects, to firstly produce a mineral concentrate before undertaking a complex and energy intensive 'cracking' process. The initial Phalaborwa process will deliver a high value cracked rare earth carbonate and studies are ongoing to investigate whether the valuable rare earth metals can be delivered as separated rare earth oxides for direct sale to industrial users. This gives us confidence that Phalaborwa will become the cornerstone of Rainbow's business in the near term.

“Alongside the recently announced metallurgical test work results, which have confirmed that the gypsum stacks are amenable to simple, direct leaching with low-cost sulfuric acid at ambient temperature and pressure, the road map to commercialising the Phalaborwa deposit is now clear. We look forward to announcing further metallurgical test work results ahead of completing an initial scoping study/preliminary economic assessment in 3Q21.

Further metallurgical test work is ongoing with ANSTO Minerals in Australia to define a preliminary processing flow sheet to support a scoping study/preliminary economic assessment for the Phalaborwa project, which is expected to be completed in 3Q21.

The maiden JORC mineral resource has been estimated based on the assay results received from 1056.3 m of auger drilling completed in December 2020. The auger drilling was independently assayed by SGS South Africa on the basis of 1.5 m interval samples with appropriate duplicate, standards and blanks used for QAQC purposes. A further programme of sonic drilling was undertaken in April 2021 primarily to recover samples for bulk density estimation – the assay results from this drill programme were not available at the time of the initial resource estimation and will be used for a further resource update ahead of a formal feasibility study for Phalaborwa. Further drilling/assay samples will also be required to upgrade the mineral resources to the measured and indicated categories required for a formal feasibility study.

The surface topography of the gypsum stacks was calculated by use of a LIDAR survey. The mineral resource estimate uses a 1.5 t/m3 estimate for the bulk density of the gypsum stacks, being the average of the bulk density calculated for competent samples collected from the sonic drilling programme (1.66 t/m3) and the bulk density calculated from more porous/weathered material near the surface of the stacks (1.33 t/m3). Further work is planned to validate the overall bulk density of the stacks to upgrade the mineral resources to the measured and indicated categories required for a formal feasibility study.

Mineral resources were estimated using a block model with a panel size of 50 x 50 x 3 m with block volume resolution down to 5 x 5 x 0.5 m. Grades, including rare earth oxides, thorium and uranium, were estimated by ordinary kriging.

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