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
