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Metallurgical tests confirm high-grade spodumene at Portugal project

5th March 2018

By: Schalk Burger

Creamer Media Senior Deputy Editor

     

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JOHANNESBURG (miningweekly.com) – Aim-listed Savannah Resources on Monday reported that Phase 2 metallurgical test work at the Mina do Barroso lithium project, in Portugal, has confirmed that conventional metallurgical processes will produce a spodumene concentrate.

“Test work confirms high-grade spodumene mineralisation with a lithium content of around 1.7% lithium oxide (Li2O) and low impurities and less than 0.5% ferric oxide, well below the 1.4% demanded by most off-takers,” Savannah CEO David Archer said.

Specifically, the heavy liquid separation (HLS) testing and the small-scale pilot testing confirm that low-iron, 6% Li2O concentrate can be produced through low-cost gravity processing.

Further, the test work suggests that at least 40% of the contained lithium can be recovered through gravity processing.

“Mina do Barroso continues to shape up as a European near-analogue to the highly successful Western Australian spodumene producers. Globally, all significant hard-rock lithium mines currently supplying the makers of lithium carbonate extract spodumene,” he said.

“An overall head grade of 1.7% Li2O was obtained for the composite sample, which was higher than expected, based on the past rock-chip results. The results established that the dominant lithium mineral is spodumene, there are low impurities, a low iron content and very little petalite (a light mineral that has a lower lithium content).

“Conventional processing techniques will produce an industry-benchmark product with low contaminants at good recoveries.”

The second series of test results confirmed the findings of the HLS tests and indicated that 30% to 40% of the lithium can be recovered by gravity as 6% concentrates. The tests also indicated that significant mass rejection of low-grade lithium residue of around 60% may be possible by using upfront gravity separation.

This work is far from optimised and further improvements are expected, Savannah added.

“The intermediate fractions still contain 3% to 4% Li2O and represent around 50% to 55% of the contained lithium.

“Further work is required to follow up on the favourable Phase 1 results to determine the best way to process this material and improve the overall lithium recovery to over 80%.”

Savannah is considering several approaches to improve overall recovery, including by recrushing the middlings material and sending it back through the dense media separation (DMS). This technique has been successfully implemented by other operators.

It is also investigating fines DMS, which is a new technique that uses gravity separation down to 0.3 mm. The technology is advanced and one plant in Australia is about to install a circuit.

“The well-established, conventional method of flotation to process fines can be used. This requires milling to less than 180 microns, which is a well-established practice.

“A preliminary unoptimised flotation test was done on the ore to determine whether could be used to recover the lithium from the middlings material. At a grind size of 180 microns, a very high figure of 71.4% of the lithium was recovered into a mass yield of 31% at a grade of 6.04% Li2O.”

This is a very encouraging result and, moving forward, the use of flotation for further lithium recovery and for feldspar recovery will be studied in greater depth, the company said.

Edited by Chanel de Bruyn
Creamer Media Senior Deputy Editor Online

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