Test work was done by ADV, but it's being repeated by GT1. The test work by ADV was very successful with a very clean division - most of the waste rock had a low lithia grade (0.11 / 0.24%) while a smaller volume was 6.05% and grades up to 6.92% were produced although this impacted recoveries. Back in 2017 high grade sold. As proven by PLS auctions, what currently sells is getting as much lithia to the customer as possible hence PLS is able to sell 5.5% grade at excellent prices.
From this ADV link:
- The 500kg sample used had a head grade of 1.29% (By implication 6.450kg lithia)
- The fines were 13.54% of this which would make them 67.7kg. The fines grade was 0.84% (0.569kg lithia)
- This implies the remaining 432.3kg at 0.5mm-6mm crush would have 5.881kg lithia. This is 1.36% so rounding has emerged somewhere as the article references 1.37%.
The test work then achieved 85.58% recovery on the crushed product (432.3kg). Before further optimization, 5.033kg of the lithia was recovered through to Spod @ 6.05%. 5.033/6.450 = 78.0% recovery. GT1 have conservatively assumed 75% recovery in their June 2022 JORC update. Those familiar with Core's DMS case which used 71.7% may be assuming the use of 75% is optimistic, when it may be the reverse!!
A recent GT1 slide deck showed material in a person's purple gloves. Unless this person has incredibly small hands, that crush was larger than 6mm so GT1 looks to be following the same pathway that A11 followed in finding that they could achieve acceptable DMS recovery rates at a 10mm crush. I suspect one of the advantages of a larger crush size is less loss as fines (can someone confirm this?)
The reference to "need for back-end flotation plant" in a recent GT1 slide may be noting that although excellent DMS results exist, there's still a significant proportion of the lithia content being lost as fines (8.8% in the example above). If a flotation circuit was added, this might take recovery rates out of the 70%'s to an industry best in class area of the 80%'s recoveries. It would add more capex but mean that more spod could be produced from a given quantity of ore processed. As GT1 are also proposing Hydroxide there's no point in pretending that this is a low-capex proposition.
Link to Ardiden Nov 2017 announcementhttps://www.ardiden.com.au/wp-content/uploads/2019/09/6860597.pdf
