NickelSearch’s testwork has proved that nickel sulphide from its Carlingup project is well suited to ore sorting, a finding which could improve its economics and unlock value.

Best results were returned from stringer mineralisation sourced from the RAV8 and RAV1 targets, which achieved 94% recovery with 63% mass reduction and 96% recovery with 44% mass reduction respectively.

RAV4 West disseminated material yielded 84% nickel recovery with the removal of 23% of the mass though only waste rock rejection was possible for RAV8 disseminated material due to it being finely and evenly disseminated.

The result is hugely positive for NickelSearch (ASX:NIS) as it offers a low-cost method of upgrading the abundant low-grade secondary nickel sulphides for commercial development.

Metallurgical test work has also returned excellent results with seven-day nitric acid digests on historical RAV8 ore returning nickel recoveries of 79% and 86% at crush sizes of 12.5mm and 8mm respectively.

The company also highlighted the isolation of an active bacteria culture from the site that delivered final nickel recoveries of 83% and 82% on milled ore when tested on historical whole ore.

“The results achieved to date with ore sorting and leaching test work are encouraging and increase our confidence that NickelSearch’s current nickel sulphide deposits can be commercially developed,” managing director Nicole Duncan said.

Company processing manager and bacterial leach specialist Tamsin Senders added that its Carlingup tenements host known nickel sulphide deposits with low-grade secondary nickel sulphides, primarily in the form of violarite.

“Historically these sulphides have not responded well to traditional processing methods, so we are thinking outside the box and investigating ore sorting followed by heap leaching to process our ores,” she added.

“Heap leaching has been used for decades in the USA and South America to recover copper from low-grade sulphides. I’m very positive on this processing pathway because this is a proven option for metal recovery from low-grade ores.”


Ore sorting

Carlingup nickel mineralisation occurs in different forms as disseminated, stringer, and massive sulphides across the Carlingup tenements.

Recent developments in ore sorting by Steinert, an ore sorting technology provider, have resulted in the ability to use up to five different sensors in combination to sort and upgrade ore.

This has found that stringer material at the project is highly amenable to ore sorting, retaining over 90% of the nickel.

It also found that while no gains were observed from sorting within the disseminated zones, the disseminated ore sorts well from waste material.


Bacteria for nickel recovery

The isolation of the bacterial culture is also massively important as some species ‘glue’ themselves to nickel sulphide with a slime they make.

This slime contains organic substances that attack the mineral which then releases the nickel in a process called ‘direct leaching’ while other bacteria take soluble iron from direct leaching to make ferric, a powerful oxidising agent that can break sulphide bonds in the ore to release nickel.

Using a local culture is advantageous as the microbes are already adapted to site conditions including saline water, elements in the ore and climatic variation.

Further amenability testing is currently underway on sorted low grade ore from RAV8, RAV1 and RAV4- West.


This article was developed in collaboration with NickelSearch, a Stockhead advertiser at the time of publishing.

This article does not constitute financial product advice. You should consider obtaining independent advice before making any financial decisions.