Viridis sets new bar for magnet rare earths recoveries

Viridis Mining & Minerals says it has achieved world-record bulk sample recoveries for ionic-adsorption clay (IAC) magnetic rare earth oxides (MREO) after ANSTO tested drill-core material from the company’s Colossus project in south-eastern Brazil.

Management today confirmed the metallurgical breakthrough that produced 76 per cent recoveries for neodymium-praseodymium (NdPr) and 65 per cent for the more valuable dysprosium-terbium (DyTb) heavy rare earth oxides.

ANSTO – the Commonwealth Government’s widely-renowned Australian Nuclear Science and Technology Organisation – was charged with the detailed work in a bid to optimise a flowsheet design to best produce a mixed rare earths carbonate (MREC) product from the bulk composite sample. The phase-one MREC test program used a 40kg bulk composite sample from Viridis’ Northern Concessions area within the Colossus operation that sits in the State of Minas Gerais.

The sample was comprised of 85 per cent drill core that produced an average grade of 4472 parts per million total rare earth oxides (TREO), with an impressive 32 per cent MREO.

To assess optimal desorption conditions, various diagnostic leach tests were conducted by ANSTO to determine the impact of reagent selection, pH levels and residence time in the solution to outline maximal operating conditions for both recoveries and operating expenditure. ANSTO produced further refinements from slurry leach testing and impurity removal, in addition to improving the separation and precipitation phases.

The company says ANSTO’s testing produced the world’s highest ionic recovery levels for MREO using a standard ammonia sulfate (AMSUL) test in a 30-minute leach cycle.

What an outstanding start to this critical work program for Colossus. The metallurgical recoveries have exceeded our expectations and to have such high recoveries across all testing conditions, highlights the robustness of the front end of the flowsheet design, which is paramount for quality control of our final product. These are significant breakthroughs which will greatly assist in providing a lower CAPEX and OPEX operation.

Moreno added that completing the remainder of the program will support the finalisation of the project’s flowsheet design and the capex and opex estimates to be used in the upcoming scoping study.

Viridis says sensitive testing on the bulk composite sample proved material savings could be made during the recovery process of the MREO and still produce output at similar levels with the benefit of reduced gangue elements and a decrease in impurity removal required in the processing steps that follow. It said notable improvements made were higher pH levels that allowed for quicker and cheaper precipitation from the leached slurry, culminating in a high basket-value MREC product.

The company is now continuing its work with ANSTO in a bid to optimise the processing details of the flowsheet and is conducting infill drilling at its promising Cupim South Extension prospect to support an updated mineral resource, which is estimated for release later this year. Work is also progressing on its scoping study, which it plans to complete in the next few months.

Viridis recently obtained a mining licence for its Cupim South deposit that contains what it says is the highest-grade IAC deposit globally and an exploration license for its Centro Sul prospect. The Colossus project has an existing mineral resource of 201 million tonnes at 2590ppm TREO and 668ppm MREO on ground comprising 239 square kilometres.

Interestingly, the resource is defined in just a 16sq km area, representing just 7 per cent of the company’s ground.

Rare earths are used in the production of many devices used in modern society including smartphone screens, computers, medical equipment, new generation light bulbs and batteries used in electric vehicles (EVs) and hybrid motor vehicles.

With continued drilling and an improved metallurgical process taking shape, Viridis is determined to prove to the market that a bigger Colossus translates into a better Colossus.

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