Saturn Metals Limited (ASX:STN) has obtained announce significant results from metallurgical test work on samples of mineralised material collected from RC drilling at the Apollo Hill deposit within its 100%-owned Apollo Hill Gold Project, 60km south-east of Leonora in the Western Australian Goldfields.
This test work is a key part of the company’s ongoing strategy to grow the Apollo Hill Mineral Resource, which was upgraded to 944,000 ounces on 28 January 20211.
Management says results demonstrate the clear potential to consider lower processing costs through simpler and scalable treatment options. Lower unit costs can in turn lead to lower cut off grades to allow for the processing of additional mineralised material, improved stripping ratios and more efficient mining processes/economies of scale.
Highlights
Exceptional Overall Recovery from Free Milling Gold
- Excellent overall gold recovery of 96.8% was obtained at typical commercial grind sizes (75 micron)
a) in intermittent bottle roll tests (IBRT) and bulk leach extractable gold (BLEG) tests of RC samples for Apollo Hill’s major material types
b) and across the deposits full grade range. Major Gravity Gold Component
- The average gravity component of the overall recovery was a very high 65.9% demonstrating the potential for efficient physical processing and lower reagent usage.
First Rate Recovery for Lower Grade Samples
- Gold recovery is consistently high across the full grade range (recovery of 97% noted for key rock types grading only 0.24g/t). This indicates the capacity for recovery from material which would normally be considered more marginal and importantly raises the potential for the use of lower cut off grades in resource calculations.
Easy Liberation
- At a coarse commercial grind size of 250 micron, average gold recovery was still impressive at 91.3% and the gravity component was very strong at 56%.
Lower Capital and Process Route Optionality
- Even at a 2mme crush, average gold recovery was an excellent 80.3%, with strong gravity recovery 47.8% showing the potential for other lower capital and simple processing methods such as early recovery of gold through screening with gravity recovery, vat leach and/or heap leach techniques.
Rapid Leach Times – Efficient Cyanidation
- At the 75 microna size fraction the majority of gold recovery (+95% of the final 24 hour recovery) was completed within only four hours, and full recovery within only eight hours, highlighting the opportunity for quick leach kinetics (throughputs) and improved capital cost efficiency.
Low Reagent Use
- Cyanide consumption was considered consistently low at an average of only 0.33kg/t. Lime addition was minimal at an average rate of only 0.13 kg/t highlighting the clean nature of the tested material types and the potential for lower reagent use (all tests completed in good quality water). Uniform Characteristics by rock type and geography
- Consistent and strong performance was noted across geography, rock type and material type suggesting the potential for simple ore scheduling. Normal Rock Processing Characteristics
- Results of the Bond Ball work index and grindability values are in line with most Archaean lode gold systems in Western Australia.
Next Steps
- The Company has recently completed a four hole, 470m, metallurgical diamond drill programme to provide additional material for the next phase of test work already underway. This work is focussing on mill-based grind size and recovery optimisation, and heap/vat leach metallurgical processing alternatives. Positive Information for inclusion in the next Resource Upgrade
- These results, and the results of the ongoing metallurgical drill core test work, will be utilised to provide important cost information for open pit optimisation studies, used as part of the planned early 2022 resource upgrade, alongside the results of Saturn’s successful 2021 drilling campaigns.