Overview
The R-42B mineral processing facility represents a cornerstone in modern metallurgical engineering, designed to optimize the extraction and recovery of precious and base metals from high-complexity ore bodies. Situated in a geologically diverse region, the R-42B project is a multi-phase development spearheaded by a consortium of industry leaders including Aris Mining Corporation and strategic partners involved in large-scale metallurgical optimization. The significance of the R-42B mine lies not only in its substantial throughput capacity—modeled at over 3,024 tonnes per hour (tph) for its primary circuits—but also in its integration of advanced semi-autogenous grinding (SAG) and ball milling technologies to achieve superior liberation of minerals.
The project is characterized by its strategic location and its role as a primary driver of regional economic stability. Geologically, the deposit consists of both oxide and fresh rock footwalls, requiring a versatile processing circuit capable of handling varying ore hardness and competency. The current operational focus at R-42B involves the transition from Phase 1 operations (targeting approximately 60,000 tonnes per day) to an expanded Phase 2 capacity, which is projected to double the total throughput to 120,000 tonnes per day by Year 5. This expansion is supported by a comprehensive technical framework that emphasizes capital efficiency, staged infrastructure deployment, and the implementation of autonomous haulage systems (AHS) to streamline feed delivery to the processing plant. The R-42B mine serves as a benchmark for high-volume, low-margin deposit management, utilizing industry-leading recovery algorithms and state-of-the-art comminution circuits.
Key Process Stages
The R-42B processing circuit is a sophisticated multi-stage system designed for maximum efficiency and mineral liberation. The flowsheet incorporates two-stage crushing, specialized grinding, and multi-stage flotation. Key stages include:
- Primary Crushing and Stockpiling: Ore is discharged via parallel streams of vibrating feeders onto a massive run-of-mine (ROM) stockpile with a 45,425-tonne capacity, providing over 52 hours of continuous feed storage.
- Grinding Circuit (SAB): The primary comminution stage features a 34′ x 18.25′ SAG mill powered by a 12.5 MW motor. This mill operates in a closed circuit with a pebble crusher (20 mm screen size) to ensure consistent feed for the secondary mills.
- Secondary Grinding: A high-capacity ball mill (28′ x 48′) operates in a closed circuit with a hydrocyclone cluster. The system is designed to achieve a target P80 grind size of 45-53 µm, essential for optimal downstream flotation.
- Classification and Desliming: Cyclone overflows are deslimed to remove ultra-fine particles that can interfere with flotation kinetics. The underflow reports to the coarse rougher stages.
- Flotation and Concentration: The circuit utilizes rougher flotation followed by regrinding of concentrates. High-grade products are further refined through three stages of cleaner flotation to produce a final bulk concentrate.
- Tailings and Filtration: Final tailings are processed through high-rate thickeners (55m diameter) and pressure filters to achieve 84-85% solids, facilitating sustainable dry-stack tailings management.
Critical Data
| Parameter | Value | Unit |
|---|---|---|
| Nominal Throughput (SAG Mill) | 3,024 | tph |
| SAG Mill Power | 12.5 | MW |
| Ball Mill Power (Primary) | 20.5 | MW |
| ROM Stockpile Capacity | 45,425 | tonnes |
| Target Grind Size (P80) | 53 | µm |
| Gold Recovery (Phase 1) | 95.1 | % |
| Tailings Filter Cake Solids | 85.3 | % w/w |
| Phase 2 Target Throughput | 120,000 | tpd |
| Flocculant Addition (Tailings) | 20 | g/t |
Technical Details and Sustainability
The technical architecture of the R-42B mine is built upon rigorous metallurgical testwork and advanced simulation modeling. Comminution tests indicate that the ore exhibits medium to hard resistance to impact breakage, necessitating the high power draw provided by the 12.5 MW SAG mill and the 20.5 MW primary ball mill. This energy-intensive process is optimized through variable speed drives (VSD), which allow operators to manage energy input based on the specific lithology of the feed—whether processing the clay-heavy footwall material or the harder rock footwall ores. The integration of pebble crushers within the SAG circuit ensures that critical-sized material is effectively reduced, preventing mill overload and maintaining a steady-state throughput of approximately 3,024 tph.
Recovery methods at R-42B leverage complex flotation chemistry. The rougher and cleaner flotation stages are governed by grade-recovery algorithms that adjust reagent dosages—including copper collectors and antimony-specific reagents—in real-time based on weightometer data located at critical points like the mill feed and crushing conveyors. The project targets a weighted average recovery of 95.1% for gold, with a significant portion of the value recovered early in the circuit via gravity concentrators, which treat a split of the secondary cyclone underflow. This “early recovery” strategy reduces the load on the downstream leaching and flotation stages, improving overall plant efficiency and reducing chemical consumption.
Sustainability is a core pillar of the R-42B operation. The facility utilizes a high-rate thickening system to manage process water, achieving a 60% w/w solids discharge from the 55m diameter thickeners before final filtration. This enables the plant to recycle a high percentage of process water, significantly reducing its environmental footprint in water-stressed regions. Furthermore, the use of dry-stack tailings, achieved via belt and pressure filters reaching 85.3% solids, eliminates the need for traditional wet tailings dams, thereby mitigating geotechnical risks and enhancing long-term environmental safety. The project’s future outlook includes further automation of the grinding and flotation circuits, which is expected to lower specific energy consumption and further enhance the project’s ESG (Environmental, Social, and Governance) profile.
Source: R-42B
Source: NI 43-101 Technical Report
This article provides an overview of mineral processing developments based on publicly available technical reports and industry analysis.
