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.
Consolidated report summaries
The following former standalone pages about this operation were consolidated here on October 25, 2026. They are retained for source traceability; dates and figures reflect each report’s own effective date and may be superseded by the current information above.
Inside the Altar Project: A Deep Dive into the 60,000 tpd Copper-Gold Flotation Circuit
Overview
Nestled in the mineral-rich province of San Juan, Argentina, the Altar Project represents a significant undeveloped copper-gold porphyry deposit poised to contribute to the global supply of critical metals. Owned and operated by Aldebaran Resources Inc., a Canadian mineral exploration company headquartered in Vancouver, this advanced-stage project is the focus of a comprehensive Preliminary Economic Assessment (PEA) detailed in a September 2025 NI 43-101 Technical Report. The project is strategically important due to its substantial scale and location in a mining-friendly jurisdiction, targeting the production of a gold-bearing copper concentrate. The envisioned operation plans to process a massive 60,000 tonnes of ore per day (tpd), leveraging a conventional but optimized flotation circuit to extract copper and gold from a blend of supergene and hypogene mineralization. With an effective date of September 1, 2025, the technical report outlines a path forward for Aldebaran Resources to develop a major, long-life mining operation, emphasizing not only the robust metallurgical process but also the economic and environmental considerations essential for modern resource projects. The Altar Project underscores the ongoing global demand for copper, a cornerstone metal for electrification and renewable energy infrastructure.
Key Process Stages
The proposed mineral processing plant for the Altar Project is designed as a high-capacity, single-line concentrator utilizing industry-proven flotation technology. The circuit is engineered to handle the specific ore characteristics, including variable arsenic content, to produce a saleable copper concentrate. The flowsheet follows a logical sequence from coarse ore reduction to fine mineral separation.
- Stage 1: Primary Crushing: Run-of-mine (ROM) ore, averaging 0.47% Cu and 0.08 g/t Au, is delivered by truck. It is either direct-dumped or stockpiled before being fed to a primary gyratory crusher. The crusher reduces the ore to a target size of approximately -6 inches (about -150 mm). The crushed product is then conveyed to a live stockpile, which acts as a buffer and feed source for the grinding circuit.
- Stage 2: SAG/Ball Mill Grinding: This two-stage comminution circuit is the heart of the size reduction process. Crushed ore is fed into a large 40 ft x 26 ft EGL (Effective Grinding Length) Semi-Autogenous Grinding (SAG) mill. The SAG mill discharge is screened; oversize (“pebbles”) are recirculated back to the SAG mill feed, while the undersize reports to a cyclone cluster. The cyclone underflow (coarse material) feeds a 26 ft x 40.7 ft ball mill operating in closed circuit with the cyclones. The final product, the cyclone overflow, is ground to a target primary grind size of P80 180 µm, liberating the copper and gold minerals for recovery.
- Stage 3: Rougher Flotation: The ground slurry enters the rougher flotation circuit at a pH of 10.5, adjusted with lime to depress pyrite. A collector, potassium amyl xanthate (PAX), is added to render the copper sulphide minerals hydrophobic. In a series of rougher flotation cells, air is introduced, causing the valuable mineral particles to attach to bubbles and float to the surface as a concentrate. The rougher tailings, containing the worthless gangue, are sent to the tailings management system, while the rougher concentrate proceeds for upgrading.
- Stage 4: Regrinding & Cleaner Flotation: The rougher concentrate is not yet pure enough for smelting. It is first reground in a stirred media regrind mill (like a tower mill) to an ultra-fine P80 of 18-20 µm to further liberate locked particles. This reground slurry then undergoes three sequential stages of cleaner flotation. Each stage (Cleaner-1, Cleaner-2, Cleaner-3) re-floats the concentrate, with middlings recirculated, to progressively increase the grade. Reagent additions are carefully staged, and pH is controlled to achieve a final concentrate grade of 26-32% Cu and 3-5 g/t Au.
- Stage 5: Concentrate & Tailings Handling: The final high-grade concentrate is thickened to 55-60% solids and then dewatered in a filter press to approximately 9% moisture for transport. All process water from thickening and filtration is recycled. Rougher tailings are thickened to ~55% solids and pumped to a conventional Tailings Storage Facility (TSF), with an alternative dry-stack filtration option noted for further study. Water is also reclaimed from the TSF for reuse, minimizing freshwater intake.
Critical Data
The following table summarizes the key design criteria and performance metrics for the Altar Project’s processing circuit, as outlined in the PEA. These figures form the basis of the project’s economic and technical viability.
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Design Throughput | 60,000 | tpd | Operating 24/7/365 |
| Hourly Throughput | 2,717 | tph | Based on 92% operating availability |
| Life of Mine (LOM) Head Grade – Cu | 0.47 | % | |
| Life of Mine (LOM) Head Grade – Au | 0.08 | g/t | |
| Estimated Average Recovery – Cu | 85 – 87 | % | |
| Estimated Average Recovery – Au | ~55 | % | |
| Target Primary Grind Size (P80) | 180 | µm | Cyclone overflow from SAG/Ball mill circuit |
| Target Regrind Size (P80) | 18 | µm | For rougher concentrate, using a tower mill |
| Final Concentrate Grade – Cu | 26 – 32 | % | Varies with supergene/hypogene ore blend |
| Final Concentrate Grade – As | 0.98 – 1.3 | % | Will incur smelter penalties; requires blending |
| Bond Ball Mill Work Index (BWI) | 16.6 | kWh/t | 75th percentile value for hardness |
| SMC Test A×b Value | 41.5 | kWh/t | Indicates moderate SAG ore competence |
Additional Interesting Data and Summary
The Altar Project’s PEA reveals several fascinating technical and strategic layers beyond the core flowsheet. A primary operational consideration is the variable arsenic (As) content in the final concentrate, projected between 0.5% and 2.2%. This is attributed to the mineral enargite (Cu3AsS4), particularly present in the supergene ore zones. High arsenic levels trigger significant penalties from copper smelters and may restrict marketability. The project plan explicitly acknowledges this challenge, noting that the concentrate will likely require blending with cleaner, low-arsenic concentrates from other sources—a common industry practice for managing deleterious elements—which will impact net smelter returns.
From a sustainability and risk management perspective, the report gives serious consideration to tailings disposal methods. The base case assumes a conventional slurry tailings storage facility (TSF) with water reclaim. However, it explicitly evaluates the alternative of a filtered “dry stack” facility. While dry stacking significantly reduces long-term environmental liability and water consumption by creating a stable, stackable tailings cake, it comes with higher capital (capex) and operating (opex) costs due to the need for large filter presses and additional material handling. This evaluation reflects the industry’s post-Brumadinho shift towards safer tailings management and the increasing importance of ESG (Environmental, Social, and Governance) factors in project design.
Economically, the scale is immense. Processing 60,000 tpd equates to nearly 22 million tonnes per year, placing Altar among the world’s larger proposed copper operations. The design recovery rates of 85-87% for copper and ~55% for gold are robust for a porphyry deposit, especially given the gold’s often refractory nature. The use of a SAG/Ball mill circuit for primary grinding and a tower mill for concentrate regrind indicates a design tailored for high throughput and efficient fine grinding, balancing energy consumption with liberation needs. The project’s location in San Juan, Argentina, offers established mining infrastructure and a provincial government supportive of responsible resource development, enhancing its execution potential. In summary, the Altar Project presents a technically sound, large-scale flowsheet that must navigate specific metallurgical challenges (arsenic) and modern environmental imperatives (tailings management) to unlock its substantial copper-gold value.
Source: NI 43-101 Technical Report | Preliminary Economic Assessment | Project: Altar Project | Date: September 2025
