Overview
The Ruby No. 5 mine represents a cornerstone of modern polymetallic mineral extraction, characterized by its high-grade ore profile and a sophisticated processing architecture designed to maximize value from complex sulfide mineralogy. Located in a geologically prolific district, the Ruby No. 5 project has emerged as a benchmark for sequential flotation efficiency, targeting the recovery of lead, zinc, copper, silver, and gold. The project is strategically significant due to its ability to process 800,000 dry tonnes per year (t/a) of mineralized material, producing high-value concentrates that meet stringent global smelting specifications.
The significance of the Ruby No. 5 mine lies in its integrated approach to comminution and beneficiation. With a Run-of-Mine (ROM) head grade boasting an average of 2.9% lead, 4.6% zinc, and 0.5% copper, alongside precious metal credits of 1.37 g/t gold and 159 g/t silver, the economic viability of the project is robust. To unlock this value, the metallurgical team developed a process flowsheet that addresses the challenges of fine-grained mineralization and mineral intergrowth. The primary objective of the circuit is the production of two distinct products: a silver-lead-copper bulk concentrate and a high-grade zinc concentrate. By utilizing advanced sequential flotation techniques, the facility achieves high recovery rates while maintaining the selectivity required to minimize deleterious elements. This technical overview explores the engineering and operational parameters that define the Ruby No. 5 processing plant, from primary crushing to the final dewatering of concentrates and tailings.
Key Process Stages
The mineral processing circuit at Ruby No. 5 is a multi-stage operation designed for continuous performance and maximum availability. The following stages outline the flow from raw ore to refined concentrate:
- Primary and Secondary Crushing: The crushing plant is designed with a nominal feed rate of 290 tonnes per hour (t/h). It processes ROM ore from an initial size of 100% passing 600 mm down to a crushed product size of 80% passing 7.12 mm. This stage utilizes a primary jaw crusher and secondary cone crushing in an open circuit to prepare the feed for the grinding section.
- Grinding and Classification: The grinding circuit is the heart of the liberation process, operating at 100 t/h with a target product size (P80) of 40 µm. This fine grind is achieved through a ball mill circuit, which operates with a design circulating load of 250%. The Bond Ball Mill Work Index (BWi) for the ore is established at 9.5 kWh/t, reflecting a relatively moderate hardness that facilitates efficient comminution at the required fineness.
- Sequential Flotation: The beneficiation process employs a sequential flotation strategy. The first stage involves the flotation of a silver-lead-copper bulk concentrate. During this stage, specific depressants are used to inhibit zinc minerals while collectors target galena and chalcopyrite. This is followed by a zinc flotation circuit where copper sulfate is added to activate sphalerite for recovery.
- Concentrate Dewatering: Concentrates are thickened in high-rate thickeners to an underflow density of approximately 68% solids. Following thickening, the concentrates undergo pressure filtration. The lead-silver concentrate filtration system is designed for 10 t/h, while the zinc concentrate filtration handles 12 t/h.
- Tailings Management and Backfill: Final flotation tailings are thickened to a slurry density of 59% solids. A portion of the processed material is diverted for use as underground backfill, with crushing products specifically sized for paste aggregate (12 mm) and cemented aggregate fill (75 mm).
Critical Data
| Parameter | Value | Unit |
|---|---|---|
| Annual Throughput (Design) | 800,000 | dry t/a |
| Milling Capacity (Design) | 100 | t/h |
| Mill Operating Availability | 8,000 | h/a |
| Crushing Plant Feed Rate | 290 | t/h |
| Grinding Product Size (P80) | 40 | µm |
| Lead Head Grade (Average) | 2.9 | % Pb |
| Zinc Head Grade (Average) | 4.6 | % Zn |
| Silver Head Grade (Average) | 159 | g/t Ag |
| Copper Recovery to Ag-Pb Conc. | 81.2 | % |
| Lead Recovery to Ag-Pb Conc. | 87.4 | % |
| Silver Recovery to Ag-Pb Conc. | 75.0 | % |
| Zinc Recovery to Zn Conc. | 80.2 | % |
| Bond Ball Mill Work Index | 9.5 | kWh/t |
| Bond Abrasion Index | 0.168 | g |
Technical Details and Sustainability
The metallurgical complexity of the Ruby No. 5 mine necessitates a rigorous technical approach to reagent management and circuit control. The requirement for a P80 of 40 µm is particularly significant, as it indicates that the valuable minerals are finely disseminated within the host rock. Achieving this grind size efficiently is paramount to ensuring high recovery rates; any deviation toward a coarser grind would likely result in poor liberation, leading to excessive metal loss in the tailings or lower concentrate grades due to mineral locking. The relatively low Bond Ball Mill Work Index of 9.5 kWh/t is an operational advantage, allowing the plant to reach this fine target size without excessive energy consumption compared to harder ore bodies found in other polymetallic districts.
From a chemical perspective, the sequential flotation circuit relies on precise pH control and the selective use of collectors. In the silver-lead circuit, the challenge is to recover over 87% of the lead and 81% of the copper while ensuring the zinc remains depressed. This is typically managed using zinc sulfate or other depressants in a pH-regulated environment. The subsequent zinc circuit requires the “activation” of sphalerite using copper sulfate, which modifies the mineral surface to allow for xanthate-based collection. The resulting silver-lead concentrate is exceptionally high-grade, with silver values reaching 2,266 g/t, making it a highly desirable product for smelters.
Sustainability and environmental stewardship are integrated into the Ruby No. 5 design through efficient water management and tailings disposal strategies. The processing plant operates with a focus on maximizing water recycle from the concentrate and tailings thickeners, significantly reducing the requirement for fresh make-up water. The use of thickened tailings (59% solids) and the integration of backfill production facilitate a reduced environmental footprint. By converting a significant portion of the waste material into paste and cemented aggregate fill (sized at 12 mm and 75 mm respectively), the mine can stabilize underground workings while minimizing the volume of material sent to surface tailings storage facilities. This circular approach to material handling not only improves the structural integrity of the mine but also aligns with modern ESG (Environmental, Social, and Governance) standards by mitigating the risks associated with large-scale surface tailings dams.
Looking toward the future, the Ruby No. 5 operation is well-positioned to adapt to fluctuations in ore grade. The design capacities for filtration (10-12 t/h) provide a buffer for processing higher-grade zones, ensuring that the plant can maintain steady-state production even when encountering variability in the mine plan. The robust data set generated during the initial phases of the project provides a solid foundation for further optimization of the flotation kinetics and reagent dosages, ensuring long-term technical and economic success.
Source: Ruby No. 5
Source: NI 43-101 Technical Report
This article provides an overview of mineral processing developments based on publicly available technical reports and industry analysis.
