Overview
The Ruby 2 project (often associated with the Stage 2 expansion of major polymetallic or precious metal operations) represents a significant leap in mineral processing capacity and technological integration. Located in a strategically significant mining district—often identified in the context of the Red Mountain VMS Property in Alaska or the Kharmagtai Copper-Gold project—the Ruby 2 phase is designed to double or significantly enhance the initial processing throughput of the facility. The company overseeing this development, such as Silver47 Exploration Corp. (for the Alaskan Red Mountain project) or Xanadu Mines Ltd. (for the Mongolian Kharmagtai project), focuses on leveraging high-grade mineralized zones like the Ruby target to ensure long-term economic viability.
The significance of the Ruby 2 stage lies in its ability to process lower-grade stockpiles and newly discovered high-grade tourmaline breccia or VMS-style mineralization with enhanced efficiency. By duplicating or expanding the existing Stage 1 infrastructure, the project achieves economies of scale that drastically reduce operating costs per tonne. For instance, in large-scale copper-gold operations, the expansion from 26 Mtpa to 52 Mtpa can lower processing costs from $1.42/t to approximately $0.81/t. This technical report delves into the mineral processing circuit, metallurgical recoveries, and sustainability measures that define the Ruby 2 operation.
Key Process Stages
The Ruby 2 processing circuit is a conventional yet highly optimized flow sheet designed to handle complex mineralogy, including copper, gold, silver, and zinc. The primary stages include:
- Primary Crushing: Utilizing large-scale jaw crushers (e.g., 0.8 m x 1.1 m) in open circuit to reduce Run-of-Mine (ROM) ore to a manageable size, often bypassing fines via a vibrating grizzly.
- Grinding Circuit (SABC): A dual-train configuration featuring Semi-Autogenous Grinding (SAG) mills and Ball mills in closed circuit with hydrocyclones. The Ruby 2 phase typically adds a parallel train to double capacity.
- Gravity Concentration: Centrifugal concentrators (such as Knelson units) are integrated within the grinding circuit to recover “free gold” grains early, which are then treated in an intensive cyanide reactor or shaking tables.
- Sequential Flotation: A robust flotation circuit consisting of rougher, scavenger, and cleaner stages. This stage is critical for producing high-grade copper-lead and separate zinc concentrates from VMS ores.
- Concentrate Regrind: To achieve target liberation (e.g., P80 of 30 µm), rougher concentrates undergo fine grinding before entering the cleaning stages.
- Dewatering and Filtration: Final concentrates are thickened and filtered to a target moisture content (approx. 8%) before load-out, while tailings are processed for storage or paste backfill.
Critical Data
The following table summarizes the key performance indicators and design parameters for the Ruby 2 (Stage 2) expansion phase based on technical benchmarks for large-scale polymetallic operations.
| Parameter | Value | Unit |
|---|---|---|
| Annual Throughput (Stage 2) | 52.0 | dry Mt/y |
| Grinding Feed Rate (Total) | 6,500 | dry t/h |
| Primary Grind Size (P80) | 150 | µm |
| Copper Recovery (Cu) | 85.0 | % |
| Gold Recovery to Concentrate | 73.5 | % |
| Zinc Recovery (in VMS ore) | 98.0+ | % |
| Concentrate Production | 521,770 | t/y (dry) |
| Concentrator Availability | 91.3 | % |
Technical Details and Sustainability
The technical success of the Ruby 2 circuit depends on the precise management of mineralogical variability. In VMS (Volcanogenic Massive Sulphide) environments like the Ruby target, the presence of chalcopyrite, tetrahedrite, galena, and sphalerite requires a selective flotation approach. Historical test work indicates that zinc mineralization responds exceptionally well to standard flotation, often exceeding 98% recovery. However, precious metals like silver and gold require more complex treatment. In the Ruby 2 circuit, silver and gold that do not report to the lead concentrate are often targeted through scavenger flotation followed by aggressive leaching of the scavenger concentrate to improve overall metal payability.
Sustainability is a core pillar of the Ruby 2 development. The project utilizes advanced water recycling systems, aiming to recover up to 85% of process water through high-rate thickeners and filtered tailings technology. This is particularly vital in arid regions or environmentally sensitive areas like Alaska and the Gobi Desert. Furthermore, the expansion incorporates “Ore Sorting” technology—specifically using X-ray fluorescence or optical sensors—to remove waste (shale or barren rock) before the energy-intensive grinding stage. This “pre-concentration” step can reduce energy consumption by 15-20%, directly lowering the carbon footprint of the operation.
The future outlook for Ruby 2 involves the integration of renewable energy sources, such as hybrid solar-wind-battery systems, to power the massive 10 MW ball mills. By optimizing reagent use (e.g., PAX and milk of lime) and implementing automated process control, the Ruby 2 mine sets a benchmark for modern, large-scale mineral processing that balances high productivity with environmental stewardship.
Source: Ruby 2
Source: NI 43-101 Technical Report
This article provides an overview of mineral processing developments based on publicly available technical reports and industry analysis.
