Oklo Resources Ltd’s (ASX:OKU) (FRA:JYA) positive results from metallurgical test work on samples from Seko within the flagship Dandoko Gold Project in Mali have highlighted simple processing options.
Work completed to date has shown that Seko exhibits straightforward, non-refractory metallurgical characteristics with a likely processing route incorporating a simple, industry-standard cyanide leach circuit.
The program included gravity separation, bond abrasion and mill work indices, leach kinetics and basic grind size variability, and initial flotation test work on three composite samples collected from SK2 prospect.
These samples represent soft oxide, transitional and fresh/hard rock gold mineralisation.
Oklo’s managing director Simon Taylor said: “The metallurgical test work results are highly encouraging in confirming the likelihood of a simple gold processing flowsheet at Seko.”
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The three separate metallurgical samples represented soft oxide mineralisation grading around 4.0 g/t gold, transitional mineralisation of around 6.5 g/t and a fresh/hard rock mineralisation grading about 3.0 g/t.
The test work was undertaken by ALS Metallurgy in Perth, Western Australia under the supervision of Lycopodium Minerals.
Seko cyanide leach and flotation recovery results.
There were cyanide leach gold recoveries of around 94% for oxide, with about 85% and 88% gold recoveries for transitional and fresh mineralisation respectively.
Leach kinetics and rapid leach times were also encouraging, with at least 96% of extractable gold dissolution within eight hours.
The oxide mineralisation is amenable to gravity concentration to recover free gold within the milling circuit.
Tests also showed flotation gold recoveries to concentrate of around 95% and 91% for transitional and fresh mineralisation respectively.
Ball mill work indices of 10.2 kWh to 16.0 kWh per tonne are comparable to other gold operations in the region.
There was moderate bond abrasion index (Ai) for oxide and fresh mineralisation of 0.05 Ai and 0.20 Ai respectively and 0.31 Ai for transitional mineralisation.
Oxide zone “particularly favourable”
Taylor said: “The results for the oxide zone, which comprises a large proportion of the mineralisation intersected to date at Seko, are particularly favourable.
“The test work results complement the excellent progress that the company is making with its resource definition drilling program at the SK1 North discovery, both of which will be essential elements in informing the forthcoming scoping study.”
As part of head grade assay analysis for the samples, multi-element ICP was undertaken with results as follows:
- Organic carbon content is low, indicating that the gold mineralisation does not contain mineral phases that are able to re-adsorb the gold cyanide in competition with activated carbon;
- Tellurium content is low, indicating that there should be no material issue with slow leaching telluride gold;
- Arsenic and antimony contents are low, indicating that these elements should not adversely affect leach kinetics;
- Silver content is low, which is advantageous for plant design in requiring a smaller elution circuit and less electrowinning capacity; and
- Mercury content is low, which is favourable for industrial hygiene.
Further test work will be conducted on samples from the SK1 and SK3 prospects.
Resource estimate upcoming
All metallurgical results will be incorporated into a scoping study, which will begin following delivery of the company’s maiden mineral resource estimate.
Drilling is ongoing at SK1 North in order to define the extents of mineralisation and this will be incorporated into the estimate.