NickelSearch Ltd (ASX:NIS) has delivered ‘exceptional’ metallurgical test-work results, unlocking value at the Carlingup Nickel Project near Ravensthorpe, Western Australia.
Notably, the company’s preliminary ore sorting test-work has indicated nickel sulphides at Carlingup can be sorted based on magnetic induction and density.
Nickel recoveries from seven-day nitric acid digests on RAV8 ore have resulted in nickel recoveries of 79% and 86% at crush sizes of 100% passing 12.5mm and 8.0mm respectively.
Importantly, an active bacterial culture has been isolated from the site and tested on historical whole ore, giving final nickel recoveries of 83% and 82% on milled ore at 35°C and 40°C respectively.
Looking ahead, NickelSearch remains focused on greenfield exploration for high-grade nickel sulphides, with a major exploration program underway this quarter.
“Unlocking value”
NickelSearch managing director Nicole Duncan said: “We are focused on unlocking value across our asset portfolio for our shareholders.
“We do that through pursuing high-grade nickel sulphide exploration targets while investigating the development of our current mineral deposits through heap leaching.
“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.”
Test-work highlights
Preliminary ore sorting test-work has now been carried out on samples of ore from seven metallurgical drill holes within RAV8, RAV4-West and RAV1.
The results from the preliminary test-work are:
- RAV8 stringer mineralisation is highly amenable to ore sorting with ~ 94% nickel recovery and removing 63% of the mass, based on sorting on density alone.
- RAV4-West disseminated material yielded 84% nickel recovery and removed 23% of the mass, sorting on both induction and density
- RAV1 stringer material gave 96% nickel recovery and removed 44% of the mass, sorting on induction alone.
- RAV8 disseminated material is finely and evenly disseminated so rejection of only waste rock is possible, but there appears to be little possibility of upgrading within the disseminated zone.
Nitric acid digestion delivered recoveries of 79% and 86% respectively and show that nickel liberation is directly proportional to crush size.
NickelSearch processing manager Tamsin Senders said: “Our Carlingup tenements host known nickel sulphide deposits.
“These contain 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.
“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 lowgrade ores.”
Next steps
NickelSearch has outlined the forward plan at Carlingup:
- The next round of bacterial oxidation tests is underway on the metallurgical samples collected earlier this year as part of the drilling campaign. Results are expected by mid-December.
- Results from completed nitric acid digests will determine the crush size of the ore and agglomeration trials will commence. Agglomeration is the process of binding fine particles to coarse particles, so that leach solution and air can pass uniformly through the heap resulting in even leaching. Results from the agglomeration trials are expected by the end of November.
- Conventional processing of nickel sulphides often considers concentrate production either through flotation or heavy media separation. Historical flotation testing on the secondary nickel sulphides has shown that these minerals respond poorly to conventional flotation, with nickel recoveries of 20% for a concentrate grade of ~9.8% nickel and heavy media separation giving nickel recoveries between 43% to 53%. Both results compare poorly to the bacterial oxidation amenability testing of +80% nickel recovery. However, a single flotation test will be conducted as part of the scoping study work, in order to confirm that flotation is not a suitable processing route for the NIS ore even with advancements in technology.
- Bacterial column tests are scheduled to commence in November.