Auric Mining Ltd (ASX:AWJ) has released results of metallurgical testwork from composite samples taken from the Jeffreys Find deposit, part of the Jeffreys Find Project in WA.
Of the results, AWJ technical director John Utley said, “These results confirm the amenability of Jeffreys Find mineralisation to conventional CIL treatment. This is another critical step in our progression towards mining at Jeffreys Find.”
CIL treatment is carbon-in-leach treatment, a gold extraction process called cyanidation where carbon is added to the leach tanks (or reaction vessel) so that leaching and absorption take place in the same tanks.
According to 911metallurgist.com: “The CIL process was developed for processing gold ores that contain preg-robbing materials such as natural absorptive carbon. These reduce the gold yield by attracting gold meant for the activated carbon. Simultaneous leaching and absorption help minimise the problem.”
The principal findings of AWJ’s testwork are encouraging and are highlighted below:
- Gravity separation and subsequent leaching of gravity tails yielded overall gold extraction between 90.16% and 94.99% by the 24-hour mark. This is the most representative interval as per toll treatment leaching residence times. It is noted that leach recovery improves to 92.78% and 96.19% after 48 hours.
- Comminution test work showed that Jeffreys Find is a relatively soft ore (Bond Ball Work Index of 14.6kWh/t) and has a very low Bond abrasion index (0.0544).
- Silver content in all samples is low. This in line with what would be expected for the Jeffreys Find deposit.
- The arsenic content is moderate, particularly in the fresh zone. However, there do not appear to be any issues with gold liberation.
- Organic carbon concentrations are low, indicating that Jeffreys Find does not have preg robbing qualities.
- Sulphur concentrations are low in the oxide/transitional composite, and high in the fresh composite. Despite this, there do not appear to be any issues with gold liberation.
- Gravity recovery was exceptionally high for the fresh composite, at 50.46%, with lower gravity recovery of 19.27% for the oxide/transitional composite. The high variability in gravity recovery is possibly due to the presence of coarse nuggetty gold.
- Reagent consumption (cyanide, lime and oxygen) are low for both oxide and fresh composites.
About the testwork
AWJ started the Jeffreys Find testwork program to determine various metallurgical parameters relevant to gold extraction through a typical toll treatment facility.
Two composite samples were prepared using percussion chips from Auric’s September 2021 RC drill program, with the first representing oxide material. This was tested primarily for leach recovery. The second composite represented transitional to fresh material and was separated into two further composites for both comminution and recovery testwork.
About the project
The Jeffreys Find Project comprises mining lease M63/242 and miscellaneous licence L63/97 and is approximately 45 kilometres northeast of Norseman in Western Australia.
Jeffreys Find drilling over a magnetic image.
Gold mineralisation identified at the Jeffreys Find Project includes the Jeffreys Find deposit and the Neo prospect around 550 metres to the northwest of the Jeffreys Find deposit.
Jeffreys Find has an Indicated and Inferred gold resource estimate at 0.5g/t cut-off grade of 1.22 million tonnes @ 1.22g/t for 47,900 ounces gold.
Jeffreys Find Mineral Resource estimate.
What’s next for AWJ
The latest testwork confirms the amenability of Jeffreys Find gold mineralisation to toll treatment, a critical step in the progression toward development.
Another key step was the grant on March 18 of miscellaneous licence L63/97 linking Jeffreys Find to the Eyre Highway, approximately 14 kilometres to the south.
The metallurgical results will contribute to a scoping study into toll treatment with completion expected in the June quarter.