Far East Gold Ltd (ASX:FEG) has reported encouraging preliminary metallurgical testwork from the Sua prospect within its Idenburg Project in Indonesia, with results pointing to high gold recoveries from conventional processing routes.
Testwork on three composite drill core samples returned total gold recovery of about 95% under combined gravity and carbon-in-leach (CIL) conditions, supporting the potential for a relatively straightforward processing flowsheet at Sua.
The program tested low-grade, average-grade and high-grade composite samples prepared from FEG drill holes at the prospect. The average-grade sample was designed to reflect the 3.7 g/t gold grade of the current inferred Sua resource.
Results showed gold recoveries were consistently high across all sample types and test conditions, with diagnostic leach work indicating that 94% to 96% of the gold is present as free cyanidable gold. That suggests most of the metal can be extracted using standard cyanidation rather than requiring more complex treatment methods.
The work also identified low silver, copper and arsenic levels in the samples tested, indicating minimal impact on gold extraction and reagent consumption, although further work is needed to confirm those assumptions across the broader resource.
Diagnostic leaching results indicate that gold in both AG and LG samples is predominantly present as free cyanidable gold, with over 90% of the gold readily amenable to cyanidation.
Note: The metallurgical test results reported do not imply that an Ore Reserve has been established and do not constitute a development or production decision.
“The preliminary metallurgical test work results on samples of Idenburg Gold Project are highly encouraging and indicate that the ore should respond well to conventional gravity / carbon-in-leach gold processing. The initial test work indicates that gold recoveries in the range 90-96% were achieved, of which about 50% was gravity recoverable gold. These early results indicate a relatively straightforward processing route for the project, which will need to be confirmed with additional metallurgical test work as the resource is better defined,” expert metallurgist Dr Mark Steemson, who reviewed the metallurgical test work, said.
Gravity and CIL emerge as preferred route
Bench-scale gravity recoverable gold tests delivered recoveries above 50% for the high-grade and low-grade samples, indicating a meaningful portion of the gold could be recovered early through gravity separation before leaching.
Follow-up bottle roll leach tests on the gravity tails then lifted overall recovery to 95%, reinforcing the case for a gravity plus CIL processing route.
Whole-of-ore bottle roll testing also produced strong results, with the average-grade sample exceeding 95% recovery, although the combined gravity and CIL approach still delivered the better overall outcome.
By contrast, intermittent bottle roll tests assessing a potential heap leach route returned materially lower recoveries, with the low-grade sample recovering about 60%. That result suggests heap leaching may be less suitable than a conventional gravity and leach circuit for Sua mineralisation.
The metallurgical work was carried out at PT Geoservices in Bekasi, Indonesia, under the supervision of Mining One Consultants, and confirms historical testwork completed by PT Iriana Mutiara Idenburg in 2007.
The latest results remain preliminary and are based on limited composite samples, meaning more detailed metallurgical work will be required as drilling continues and the resource is further defined.
What's next
Additional testwork will be carried out to refine the optimal process route, validate recovery assumptions and better understand reagent consumption as the company advances the Sua prospect toward future development studies.
The company also recently resumed diamond drilling at its Mount Clark West (MCW) copper-gold target in Queensland after wet-season rainfall disrupted operations in December and January.