JOHANNESBURG (miningweekly.com) – ASX-listed Northern Minerals said on Thursday that the pilot scale testwork at its Browns Range project, in the Northern Territory, had delivered “excellent” recovery of heavy rare earths oxide (HREO) and that it had confirmed two simple and robust flowsheet options.

Testwork, in conjunction with earlier bench testing, had confirmed up to 90% improved HREO recoveries, and reinforced the processing advantages of the Browns Range xenotime mineralisation, the company stated.

The pilot plant testwork was completed in January, using a 90 t bulk sample collected from the Wolverine and Gambit West deposits. The testing was undertaken at the SGS Lakefield Oretest facility, in Perth, on the two preferred flowsheet options: magnetic separation followed by cleaner flotation circuit and the whole ore flotation circuit.

“The outcomes from the pilot plant testing have exceeded our expectations and built even more confidence in the Browns Range project. These results, and the significant increase in our Joint Ore Reserves Committee-compliant resource estimate announced earlier this week, are very positive steps forward, which we expect will have a direct and positive impact on the economics and life of our proposed mining operation.”

“The pilot plant has proven both flowsheet options are robust and are suitable to be scaled up to a commercial operation. Final selection of the beneficiation flowsheet will be done in conjunction with cost and operating data from the Browns Range prefeasibility study (PFS),” said MD George Bauk.

Data from the pilot plant testwork would be modelled within the Browns Range PFS, which is due for completion by mid-2014. The mineral concentrate from the pilot run would now be used for hydrometallurgical pilot plant testing at the Australian Nuclear Science and Technology Organisation, or ANTSO, which is due to start in March.