As gold prices continue to surge to new highs, Astral Resources NL (ASX:AAR) has reported “outstanding” metallurgical testwork results for the Hestia, Eos and Iris deposits at its 100%-owned Mandilla Gold Project in Western Australia. Results included gold recoveries of up to 99.5%, reconfirming the exceptional metallurgical characteristics of the Mandilla project.
The metallurgical results at Hestia, Eos and Iris demonstrate extremely high gold recoveries, fast leach kinetics and low reagent consumptions. These were consistent with the results previously achieved at the Theia — Astral’s flagship deposit at Mandilla.
Astral reported extremely high gravity gold recoveries and very rapid leaching across the three deposits. At a 212µm grind size, it achieved final gold recoveries after only eight hours of leaching of:
- 96.5% gravity recovery, 99.5% final recovery for Hestia;
- 17.9% gravity recovery, 98.8% final recovery for Eos; and
- 66.8% gravity recovery, 96.5% final recovery for Iris.
Astral Resources managing director Marc Ducler explained the significance of the results and how they work to de-risk the project:
“The exceptional metallurgical results for Hestia, Eos and Iris continue to highlight the outstanding metallurgical characteristics of the Mandilla Gold Project. Typically, gold project studies in the Eastern Goldfields report initial metallurgical results based on 1,000ppm cyanide concentrations and 75µm grind sizes. The confidence in the Mandilla Gold Project gained from prior studies allowed us to successfully test much lower cyanide levels at much coarser grind sizes that would deliver very low processing costs yet still achieve sector-leading gold recoveries.
“To date, we have conducted 20 gravity and leach tests at Mandilla, with the gold remaining in the assayed tail averaging 0.02g/t of gold. This demonstrates that the 95.7% gold recovery assumption used in the Scoping Study, while considered high by industry standards, is potentially conservative when considering the excellent metallurgical properties being demonstrated at Mandilla.
“These new results significantly de-risk Mandilla, confirming the ability to generate high gold recoveries in easily achievable, real-world processing plant conditions.
“This will positively impact the metrics and economics of the Mandilla Gold Project Pre-Feasibility Study which is expected to be completed in the June quarter 2025.
“I note that, in the Scoping Study announced on 21 September 2023, no contribution was included for Iris where a Mineral Resource of 115,000 ounces is currently mapped.
“However, in light of these metallurgical results as well as the increase in gold price since the Study was released, it is anticipated that ore from Iris may be included as part of the Pre-Feasibility Study.
Drilling progressing well
Astral also reported that the first phase of an in-fill RC program at the Theia deposit was recently completed with 70 holes drilled for 6,500 metres of drillling.
The drill rig has since relocated to the Feysville Gold Project to undertake a 34-hole (3,750 metres) program to test for extensions to the Kamperman deposit, with seven of the 34 holes completed. Notably, the first three holes — including a 200-metre step-out to the north and the two most north-eastern step-outs — all intersected significant quartz and sulphide mineralisation, a characteristic of the lithologies that host mineralisation elsewhere at Kamperman.
Ducler commented, “Turning to exploration, drilling activities are progressing well, with the latest phase of in-fill RC drilling at Theia completed. The drill rig has since been relocated to Feysville to complete further extensional and in-fill drilling at Kamperman with seven holes already completed.
“Importantly, step-out holes up to 200 metres further north of the current known extents of gold mineralisation have intersected significant quartz and sulphide mineralisation which is similar in characteristic to the lithologies which host gold mineralisation at Kamperman.
“With mineral resource estimation work currently underway at Feysville, the team has also taken the opportunity to refine the geological models for the Hestia and Eos deposits.
“Updated MRE’s are now expected later this month for Think Big, Rogan Josh and Kamperman at Feysville, with Hestia and Eos to follow later in the December Quarter.”
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