AMN - DRC: “Outstanding” tin, tantalum and niobium test results

AVZ Minerals has produced high-grade cassiterite concentrate from alluvial material at Manono Lithium and Tin Project in the DRC with strong recoveries of tin, tantalum and niobium. The company’s managing director Nigel Ferguson has described the test-work results as being “simply outstanding”.

Effective liberation and separation show amenability to conventional metallurgical processing methods for tin and tantalum.

The tests show that a high-grade, low-impurity cassiterite concentrate can be produced grading 71.7% to 73.2% tin, which equates to 91% to 93% cassiterite.

A separate high-grade tantalum product of between 17% to 21% Ta2O5 was also produced.

The tantalum product streams are predominantly coltan (columbite-tantalite) and returned niobium grades of between 17% to 21%.

The metallurgical test program was designed to assess a conceptual process flowsheet for the treatment of alluvial tin and tantalum minerals from Manono.

The program employed conventional metallurgical processes specifically targeted to separate tantalum minerals, predominantly coltan from the tin, which resides entirely as cassiterite.

Two master composites were prepared using hand-selected artisanal concentrate samples from six alluvial zones across the Manono licence.

The two composite samples were screened at 0.5mm with the high-grade products residing in the coarser (+0.5mm) fraction. The coarse fraction was then sent for magnetic separation and conducted at two different magnetic intensities.

The low-intensity magnetic stream contains predominantly iron-bearing waste minerals, such as haematite, while the high-intensity stream contains tantalite, columbite and other tantalum bearing minerals. Cassiterite, if well liberated, reports to the non-magnetic stream.

The finer fraction (-0.5mm) reported for a gravity separation step to remove low-density gangue minerals before undergoing the same magnetic separation process.

The broad intent of the metallurgical program was to prove the amenability of conventional, low-cost process equipment to separate tin and tantalum products which offer maximum value when sold as individual product streams.

Ferguson said: “The company has been 100% focused on developing the hard rock assets of the Manono project and presenting the recently completed definitive feasibility study.

“Some test work on the substantial Manono alluvial tin fields was able to be included in the DFS, however, we purposely left any detailed work on the alluvial tin fields until a later stage in the project.

“We have previously announced some encouraging results from our alluvial test-work program but this latest set of results are simply outstanding with regards to recovery of not only tin but tantalum and niobium.”

He said: “Given the excellent results reported from our first two composite samples, the company will embark on more detailed test-work programs to define the potential benefit of metals within the alluvial fields at Manono and what they can add to the project revenue stream.

“Gross revenue in the DFS included that from alluvial tin contributes approximately US$126 million over life of mine and is a conservative 0.8% of the total gross revenue of US$15.242 billion LOM.

“Given these excellent results, the company will now look to maximise these potential revenue streams including any potential revenue credits from recovered tantalum and niobium.”

Investigation will also be undertaken into beneficiation of the concentrates into ingots through establishing a furnace at Manono, such as was present during previous tin operations.

www.avzminerals.com.au