This profile is based on the NI 43-101 Technical Report with an effective date of 6 June 2025. The processing route comprises conventional crushing, grinding, and flotation to produce a copper-gold concentrate, with cyanide leaching of flotation tailings to recover additional gold and copper as doré and precipitate.
Report context
The Boda-Kaiser Copper-Gold Project in New South Wales, Australia, comprises two porphyry deposits with similar mineralogy but different metallurgical responses. The most substantial metallurgical testwork program was conducted in 2023, forming the basis for a preliminary engineering design completed in April 2024. This profile draws on two source documents: the Boda-Kaiser Metallurgical Development Program (Scott Dalley Francks, 2024) and the GRES North Molong Porphyry Scoping Study (GRES, 2024). The 2023 program used half-HQ core to generate 21 variability samples and two master composites from 11 Boda and 10 Kaiser drillholes.
Processing route
Comminution and grinding
The scoping-study flowsheet envisions run-of-mine material fed into a two-stage crushing circuit comprising one primary gyratory crusher and two secondary cone crushers, producing a final crushed product of 45 mm onto a crushed ore stockpile. Material is reclaimed to two high pressure grind rolls in closed circuit with four screens. Ground material reports to two 24 MW ball mills in closed circuit, targeting a grind size of 106 µm.
Comminution testing of 21 samples indicates relatively hard ore with average abrasiveness. The design basis uses 85th percentile values for most parameters: a ball mill work index of 21.4 kWh/t, rod mill work index of 26.9 kWh/t, and a crushing work index of 18.5 kWh/t (estimated from SMC testing). The SAG mill comminution (SCE) design value is 14.6 kWh/t at the 85th percentile. Average ore specific gravity is 2.85 kg/L.
Flotation circuit
A substantial program of 130 small-scale flotation tests identified a rougher-regrind-cleaner-recleaner circuit as optimal. Primary grind is 106 µm, with regrind of rougher concentrate to 30 µm. Kaiser ore requires a finer primary grind than Boda for equivalent performance.
Locked cycle testing (10 kg samples, 5–6 cycles) was conducted on both master composites. For the Boda master composite, final concentrate represented 0.72% mass, grading 24.5% copper and 43.7 g/t gold, with recoveries of 84.5% copper and 75.4% gold. For the Kaiser master composite, final concentrate was 0.75% mass, grading 26.9% copper and 26.8 g/t gold, with recoveries of 78.7% copper and 66.5% gold.
In the scoping-study flowsheet, ground material reports to two lines of rougher flotation. Rougher concentrate is reground to a P80 of 27 µm in two HiG mills, then reports to cleaner and re-cleaner circuits. Final copper concentrate reports to a concentrate thickener.
Analysis of cleaner flotation tailings indicates the remaining copper-bearing minerals are fine-grained and, when not liberated, are strongly associated with silicates. The report notes further optimisation may be possible with additional cleaning stages or technologies such as Jameson cells. Only fluorine was measured above penalty limits (>150 ppm) in concentrate analysis.
Cyanide leaching of tailings
The flowsheet incorporates cyanide leaching of both cleaner and rougher flotation tailings. Cleaner flotation tailings contain approximately 5–7% of feed gold and 3–4% of feed copper. Testwork on these tailings showed 70–80% gold leach recovery and 40–55% copper extraction. Rougher flotation tailings contain 10–25% of feed gold, with 60% gold recovery observed in leaching.
In the proposed design, cleaner circuit tailings report to a hybrid carbon-in-leach circuit comprising two leach tanks followed by six CIL tanks. Loaded carbon reports to an elution circuit. CIL tailings are thickened and filtered, with solution reporting to a precipitation circuit via addition of peroxide and sodium hydrosulphide. The precipitate is thickened via a 1 m thickener. CIL tailings are combined with rougher tailings, thickened, and cyanide removed via a detoxification circuit. The report states that testing in respect to the copper precipitate has not yet occurred.
Overall recoveries
The scoping study used a blended design basis of 82% copper and 75% gold total recovery. Individual deposit estimates from the preliminary metallurgical study are:
- Boda: 87% copper and 81% gold to saleable concentrate
- Kaiser: 80% copper and 71% gold to saleable concentrate
Key reported parameters
| Parameter | Unit | Basis | Value |
|---|---|---|---|
| Primary grind P80 | µm | Design | 106 |
| Regrind P80 (rougher concentrate) | µm | Design | 27 |
| Ball mill work index (design) | kWh/t | 85th percentile | 21.4 |
| Rod mill work index (design) | kWh/t | 85th percentile | 26.9 |
| SCE (design) | kWh/t | 85th percentile | 14.6 |
| Crushing work index | kWh/t | Estimated (SMC) | 18.5 |
| Boda copper recovery to concentrate | % | Locked cycle testwork | 84.5 |
| Boda gold recovery to concentrate | % | Locked cycle testwork | 75.4 |
| Kaiser copper recovery to concentrate | % | Locked cycle testwork | 78.7 |
| Kaiser gold recovery to concentrate | % | Locked cycle testwork | 66.5 |
| Boda final concentrate copper grade | % | Locked cycle testwork | 24.5 |
| Boda final concentrate gold grade | g/t | Locked cycle testwork | 43.7 |
| Kaiser final concentrate copper grade | % | Locked cycle testwork | 26.9 |
| Kaiser final concentrate gold grade | g/t | Locked cycle testwork | 26.8 |
| Overall copper recovery (design blend) | % | Scoping study basis | 82 |
| Overall gold recovery (design blend) | % | Scoping study basis | 75 |
| Gold leach recovery (cleaner tailings) | % | Testwork | 70–80 |
| Gold leach recovery (rougher tailings) | % | Testwork | 60 |
| Whole-of-ore gold leach (P80 106 µm) | % | Testwork | ~75 |
| Whole-of-ore copper leached | % | Testwork | 20–25 |
| Gravity gold recovery (Boda master composite) | % | Testwork | 64 |
| Gravity gold recovery (Kaiser master composite) | % | Testwork | 25 |
Project website: https://www.listcorp.com/asx/alk/alkane-resources-limited/news/boda-kaiser-regional-exploration-update-3211249.html
Technical qualifications
The metallurgical data in this profile is drawn from testwork conducted in 2023 on drill core samples, supplemented by a 2022 program that showed significantly different gravity gold recovery results (0–3%). The processing flowsheet described is from a scoping study (GRES, April 2024) and represents a preliminary engineering design, not an operating plant. Cyanide leaching of flotation tailings and copper precipitate production are proposed unit operations; the report explicitly states that testing for copper precipitate has not yet occurred. The scoping study design basis of 82% copper and 75% gold recovery is a blended assumption; individual deposit testwork results differ (Boda 84.5% Cu, 75.4% Au; Kaiser 78.7% Cu, 66.5% Au to concentrate). Variability samples showed results similar to the master composites. This profile does not include resource estimates, economic analysis, or current project status.
Source: Boda-Kaiser Copper-Gold Project, New South Wales, Australia – NI 43-101 Technical Report, effective date 6 June 2025, Version 2.0. Sections 13 (Mineral Processing and Metallurgical Testing) and 17 (Recovery Methods).
