The Altar Project preliminary economic assessment proposes a 60,000 tpd flotation concentrator to recover copper and gold from a porphyry deposit, based on extensive metallurgical testwork.
Report context
This report is a Preliminary Economic Assessment (PEA) Technical Report for the Altar Project, dated September 2025 and prepared by SRK Consulting (U.S.), Inc. The recovery methods section describes metallurgical testwork results and a proposed processing flowsheet for a copper-gold flotation concentrator.
Processing route
Proposed concentrator flowsheet
The preliminary flotation concentrator flowsheet includes primary crushing followed by grinding in a SAG mill/ball mill grinding circuit, rougher flotation, regrinding of the rougher concentrate and three stages of cleaner flotation. The proposed design capacity is 60,000 tpd, operated on a 365 day/year, 24 hour/day schedule with 92% operating availability.
Crushing (proposed design)
Run of mine (ROM) material will be trucked to the primary gyratory crusher and either direct dumped into the crusher feed bin or dumped on a stockpile. Stockpiled material would be rehandled with a front-end loader. ROM material will be crushed to about -6 inches and conveyed to the crushed stockpile.
Grinding (proposed design)
Material reclaimed from the crushed material stockpile will be fed to a 40 ft x 26 ft EGL SAG mill. The SAG mill discharge will pass across a pebble screen, with oversize conveyed back to the SAG mill feed. The need for a pebble crusher will be assessed during the next phase of study. Screen undersize will be classified in a cyclone cluster. Cyclone underflow feeds a 26 ft diameter x 40.7 ft ball mill operating in closed circuit with cyclones. Cyclone overflow, classified at 80% passing P80 180 µm, advances to copper rougher flotation.
Flotation (proposed design)
Cyclone overflow flows to the rougher flotation conditioner where slurry is conditioned with potassium amyl xanthate (PAX) at pH 10.5 adjusted with lime. Rougher flotation produces a rougher concentrate and a final rougher tailing. Rougher tailing is pumped to the tailing storage facility. Rougher concentrate is reground to about P80 18–20 µm in a stirred media regrind mill (tower mill) in closed circuit with cyclones. The reground rougher concentrate is upgraded in three stages of cleaner flotation to produce a final concentrate.
Rougher flotation retention time is 23 minutes, based on laboratory retention time multiplied by 2.5. Cleaner-1 retention time is 15 minutes, Cleaner-2 is 12.5 minutes, and Cleaner-3 is 10 minutes.
Concentrate thickening and filtration (proposed design)
Final flotation concentrate will be pumped to a thickener and thickened to about 55–60% solids, then filtered in a filter press to about 9% moisture. Filtered concentrate will drop into a covered load-out area for truck transport. Thickener overflow and filtrate will be recycled to the process water tank.
Tailings thickening and TSF (proposed design basis with alternative)
Rougher flotation tailings and cleaner-scavenger flotation tailings will be combined in the tailing thickener and thickened to about 55% solids, then pumped to the tailing storage facility (TSF). Thickener overflow is pumped to the process water tank. Water will also be reclaimed from the TSF. Alternatively, tailings could be disposed in a dry stack TSF, with thickened tailings filtered in a filter press to about 15% moisture. The report notes dry stack disposal would increase capex and opex.
Key reported parameters
| Parameter | Units | Value | Basis |
|---|---|---|---|
| Production schedule | Design | ||
| Operating days per year | days | 365 | Design |
| Hours per day | hours | 24 | Design |
| Ore tonnes per day | tpd | 60,000 | Design |
| Ore tonnes per hour | tph | 2,717 | Design |
| Operating availability | % | 92 | Design |
| Ore grade (LOM) | Testwork/LOM estimate | ||
| Cu | % | 0.47 | Testwork |
| Au | g/t | 0.08 | Testwork |
| Estimated average recovery (LOM) | Testwork | ||
| Cu | % | 85–87 | Testwork |
| Au | % | 55 | Testwork |
| Estimated concentrate quality | Testwork | ||
| Cu | % | 26–32 | Testwork |
| Au | g/t | 3–5 | Testwork |
| As | % | 0.98–1.3 | Testwork |
| Comminution | Testwork | ||
| SMC, Axb | kWh/t | 41.5 | Testwork |
| CWi (Porphyry) | kWh/t | 7.89 | Testwork |
| CWi (Rhyolite) | kWh/t | 5.86 | Testwork |
| Ai | g | 0.11 | Testwork |
| BWI (75th percentile) | kWh/t | 16.6 | Testwork |
| Primary grind size | P80 µm | 190 | Design |
| Conc regrind size | P80 µm | 18 | Design |
| Rougher flotation reagents | Testwork | ||
| Lime | g/t | 1,000 | Testwork |
| Potassium amyl xanthate | g/t | 7 | Testwork |
| MIBC | g/t | 16 | Testwork |
| pH | 10.5 | Design | |
| Flotation retention time (lab x 2.5) | minutes | 23 | Testwork |
| Cleaner-1 flotation reagents | Testwork | ||
| Lime | g/t | 400 | Testwork |
| Potassium amyl xanthate | g/t | 7 | Testwork |
| MIBC | g/t | 8 | Testwork |
| pH | 11 | Design | |
| Retention time (lab x 2.5) | minutes | 15 | Testwork |
| Cleaner-2 flotation reagents | Testwork | ||
| Potassium amyl xanthate | g/t | 2 | Testwork |
| MIBC | g/t | as needed | Testwork |
| pH | 11 | Design | |
| Retention time (lab x 2.5) | minutes | 12.5 | Testwork |
| Cleaner-3 flotation reagents | Testwork | ||
| Potassium amyl xanthate | g/t | 1 | Testwork |
| MIBC | g/t | as needed | Testwork |
| pH | 11 | Design | |
| Retention time (lab x 2.5) | minutes | 10 | Testwork |
| Concentrate thickening & filtration | TBD | Not yet determined | |
| Tailing thickening & filtration | TBD | Not yet determined |
Project website: https://aldebaranresources.com/projects/altar-copper-gold/overview/
Technical qualifications
The report states that metallurgical testwork demonstrated copper and gold values can be effectively recovered using industry-accepted flotation technologies. Due to expected high arsenic grades in the concentrate, it is likely the copper concentrate will incur penalties and will require blending with low arsenic concentrates prior to smelting.
Concentrate grade will vary depending on whether supergene or hypogene material is being processed. Supergene material contains secondary copper sulphide minerals (chalcocite and covellite) with higher copper content, while hypogene material consists primarily of chalcopyrite with lower copper content. Arsenic in concentrate is expected to range from about 0.5–2.2% As, with the highest levels expected when processing supergene material due to the arsenic-bearing copper mineral enargite (Cu₃AsS₄).
The report notes concentrate thickening and filtration, and tailing thickening and filtration, are designated as TBD (to be determined). Flotation retention times are based on laboratory retention time multiplied by 2.5.
Source: Altar Project PEA Technical Report, September 2025, SRK Consulting (U.S.), Inc., Sections 17 Recovery Methods and 17.1 Process Description.
