Chalice Mining Ltd’s (ASX:CHN) (OTCMKTS:CGMLF) (FRA:C8U) Phase 2 metallurgical test-work at its Julimar Nickel-Copper-Platinum Group Element (PGE) Project, in Western Australia, has shown high palladium-nickel-copper recoveries.
The test-work has also displayed the ability to produce two commercially attractive concentrates using conventional flotation techniques:
- Copper-PGE concentrate grading 24.7% copper, 173 g/t palladium, 22 g/t platinum, with metal recoveries of 80.9% copper, 60.2% palladium, 37.6% platinum; and
- Nickel-PGE concentrate grading 12.2% nickel, 24.1 g/t palladium, 6.9 g/t platinum, with metal recoveries of 70.7% nickel, 26.1% palladium, 36.3% platinum and an iron:magnesium oxide ratio of around 8:1 – with cobalt assays pending.
The copper concentrate is considered to have sufficient copper and precious metal grades to be attractive to a diverse range of customers and the nickel concentrate is also considered to have sufficient nickel and precious metal grades to be commercially attractive.
“Commercially attractive concentrates”
Chalice managing director Alex Dorsch said: “Our Julimar discovery hosts a significant amount of critical, clean energy metals such as palladium, platinum, nickel, copper and cobalt.
“In such a diverse metal deposit, the ability to produce high-value, commercially attractive concentrates using a simple processing flowsheet is critical.
“The results from our second phase of metallurgical test-work have confirmed our hypothesis that widely used, simple flotation concentration techniques would be applicable for the deposit.
“The two concentrates produced in the locked-cycle test appear to be high quality, and are therefore expected to be very commercially attractive to a range of customers – a very promising result and another important de-risking step for Julimar.
“Variability test-work continues on the other mineralisation styles found at Julimar, with promising initial results from base metal concentration.”
Phase 2 program
Mineralogical and metallurgical work completed to date in the Phase 2 program includes:
- Sulphide flotation test-work on seven composite samples compiled from drill samples collected from the Gonneville G1, G2, G3, and G5 sulphide zones (awaiting precious metal assay results);
- Locked-cycle sulphide flotation test-work (LCT) on a composite metallurgical sample (JSG1) compiled from the Gonneville G1 and G2 sulphide zones;
- Leach test-work at different grind sizes and temperatures on two composite metallurgical samples compiled from oxide mineralisation overlying the Gonneville Intrusion; and
- QEMSCAN and laser ablation analysis of concentrates to identify the location and deportment of the platinum group minerals (awaiting results).
LCT test-work on composite sample JSG1 produced the two commercially attractive concentrates and optimisation work is now underway to refine the flowsheet and additional variability test-work and optimisation of grind size, temperature, and reagent use.
LCT is planned for the G6-11 Zones - which were discovered after the Phase 2 program commenced.
Variability sulphide flotation
Initial sulphide flotation tests have been completed on a further six composites (JSG3, JSG5, JSG6 and yearly composites, JSMC1-4) indicating that commercially attractive concentrates may be produced even at low copper and nickel head grades.
Copper concentrate grades generally ranged between 13% and 27% copper, with copper recoveries ranging from 58% to 87% (dependent on head grade).
Except for the low head grade composites (JSG5 and JSG6), nickel concentrate grades ranged between 4.5% and 17.3% nickel, with recoveries ranging from 54% to 79% (dependent on head grade).
All other assays (palladium, platinum, and gold, as well as potential deleterious elements) in the variability concentrates are pending.
Oxide test results
Variability test-work on two oxide samples has indicated that palladium and gold can be extracted using a leach process.
Results from the northern area JON1 (head grade 1.37 g/t palladium, 0.06 g/t gold) indicated extraction of 76% palladium and 95% gold at a P80 grind size of 10µm.
Results from the southern area JOS1 (head grade 2.02 g/t palladium, 0.59 g/t gold) at a coarser grind indicated extraction of 76% palladium and 95% gold at a P80 grind size of 26µm.
The leach results continue to demonstrate that the oxide mineralisation at Gonneville may impact overall project economics, and while platinum and other metals within the oxide zones are not amenable to the leach process, the company believes they would likely have minimal impact on project economics given the low grades in the oxide zone.
Further test-work is underway to determine the effect on PGE recovery over a range of grind sizes and temperatures, as well as the optimal techniques to recover metals from solution.
Locked cycle testwork results from cycles 1-5 on JSG1.
Forward plan
Chalice is fully funded to continue its 6-rig resource drill-out and comprehensive metallurgical test-work program at Julimar with around $132 million in cash (as of January 31, 2021).
Ongoing and planned activities include:
- A 160,000-metre resource definition drilling program is underway with three RC and three diamond rigs;
- Down-hole EM Geophysics is planned to identify potential high-grade targets for follow-up drilling;
- The Phase 2 metallurgical test-work program is continuing on additional sulphide composites and optimisation work is continuing on the oxide leach process. Further test-work is planned for the new zones identified after the program began;
- The company has engaged the Geological Survey of WA (GSWA) and a specialist consultant to conduct initial geochemical analysis and metallogenesis studies with the aim of improving its geological and mineralogical understanding of the discovery and enhancing targeting capability as it searches for similar discoveries; and
- Initial wide-spaced soil sampling and Moving Loop EM programs have commenced at the Hartog EM Anomaly with results expected to assist in determining whether Julimar has the potential to host multiple nickel-copper-PGE mineralised systems.
Dorsch said: “There is a lot more work do to in order to fully understand the deposit’s mineralogical, metallurgical, processing and marketing outcomes, and we continue to build that understanding ahead of the maiden mineral resource estimate, targeted for mid-2021.”
