Overview
The Lexindin (H Zone) project represents a significant milestone in the development of high-grade polymetallic assets, specifically focused on the extraction and processing of silver, lead, zinc, copper, and gold. Located in a geologically complex region characterized by Volcanogenic Massive Sulphide (VMS) and epithermal mineralization, the H Zone has emerged as a primary focus for metallurgical optimization and production scaling. The project is currently managed with an emphasis on maximizing metal recoveries through a sophisticated sequential flotation circuit, which is essential for handling the diverse mineralogical associations present within the orebody.
The significance of the Lexindin (H Zone) lies not only in its robust metal grades—boasting an average head grade of 2.9% Lead and 4.6% Zinc—but also in its potential to serve as a long-term supplier of critical and precious metals. With a design throughput of 800,000 tonnes per annum (t/a), the processing facility is engineered to balance high availability with the precision required for ultra-fine grinding. The H Zone mineralization typically requires a primary grind size of 80% passing (P80) 40 micrometers (μm) to achieve adequate liberation of galena, sphalerite, and chalcopyrite from the host pyrite and gangue minerals. This technical complexity necessitates a multi-stage comminution and flotation strategy that incorporates advanced filtration and tailings management systems to ensure both economic viability and environmental sustainability.
From a strategic perspective, Lexindin’s processing philosophy centers on the production of high-value concentrates. By utilizing sequential flotation, the plant can effectively separate lead and copper into a combined silver-lead concentrate while producing a separate, high-grade zinc concentrate. This approach maximizes the payable metal content and reduces the impact of penalties associated with cross-contamination in the smelting process. As the global demand for base and precious metals continues to grow, the technical successes demonstrated at the Lexindin (H Zone) provide a blueprint for the efficient exploitation of complex polymetallic deposits worldwide.
Key Process Stages
The Lexindin (H Zone) mineral processing circuit is a robust, integrated system designed for continuous operation and high metal recovery. The flowsheet follows a standard yet highly optimized sequence of comminution, classification, flotation, and dewatering. Below are the primary stages of the processing circuit:
- Primary and Secondary Crushing: The Run-of-Mine (ROM) ore, with a feed size of 100% passing 600 mm, undergoes a multi-stage crushing process. The design throughput for the crushing circuit is 290 tonnes per hour (dry), producing a final crushed ore product with a P80 of approximately 7.12 mm. This stage ensures a consistent feed for the downstream grinding circuit.
- Grinding and Classification: The grinding circuit is designed for a throughput of 100 tonnes per hour. It features a ball mill operating in closed circuit with hydrocyclones to achieve a fine primary grind of 80% passing 40 μm. The circuit maintains a high circulating load of 250% to prevent over-grinding of heavy sulphide minerals.
- Sequential Polymetallic Flotation: This is the core of the Lexindin recovery process. The circuit utilizes sequential flotation to separate the various metallic components:
- Silver-Lead-Copper Flotation: In the first stage, copper and lead minerals are co-floated along with silver. Advanced reagents are used to depress zinc minerals (sphalerite) while floating galena and chalcopyrite.
- Zinc Flotation: The tailings from the first stage are conditioned to activate the zinc minerals, which are then recovered into a high-grade zinc concentrate.
- Concentrate Cleaning and Regrinding: Each rougher concentrate is subjected to multiple stages of cleaning. A regrind stage may be employed for the zinc rougher concentrate to further liberate fine-grained sphalerite from pyrite, ensuring the final product meets smelter specifications.
- Filtration and Dewatering: The final silver-lead and zinc concentrates are sent to dedicated filtration units. The lead concentrate filtration has a design capacity of 10 t/h, while the zinc concentrate filtration handles up to 12 t/h. These stages reduce the moisture content to approximately 8-10% for shipping.
- Tailings Management: The final plant tailings are processed for disposal. A portion of the tailings is converted into paste aggregate fill (100% passing 12 mm) or cemented aggregate fill (100% passing 75 mm) to be used as underground backfill, while the remainder is sent to a secure tailings storage facility.
Critical Data
The following table summarizes the key operational parameters and metallurgical performance metrics for the Lexindin (H Zone) processing plant.
| Parameter | Value | Unit |
|---|---|---|
| Annual Throughput Capacity | 800,000 | t/a (dry) |
| Design Throughput – Crushing | 290 | t/h (dry) |
| Design Throughput – Grinding & Flotation | 100 | t/h (dry) |
| Operating Availability – Grinding | 8,000 | h/a |
| Bond Ball Mill Work Index (BWi) | 9.5 | kWh/t |
| Primary Grind Size (P80) | 40 | μm |
| ROM Head Grade – Lead (Pb) | 2.90 | % |
| ROM Head Grade – Zinc (Zn) | 4.60 | % |
| ROM Head Grade – Copper (Cu) | 0.50 | % |
| ROM Head Grade – Gold (Au) | 1.37 | g/t |
| ROM Head Grade – Silver (Ag) | 159.0 | g/t |
| Lead Recovery to Ag-Pb Concentrate | 87.4 | % |
| Zinc Recovery to Zn Concentrate | 80.2 | % |
| Copper Recovery to Ag-Pb Concentrate | 81.2 | % |
| Silver Recovery to Ag-Pb Concentrate | 75.0 | % |
| Ag-Pb Concentrate Grade (Lead) | 47.4 | % Pb |
| Ag-Pb Concentrate Grade (Silver) | 2,266 | g/t Ag |
Technical Details and Sustainability
The technical success of the Lexindin (H Zone) processing plant is rooted in its ability to manage complex mineral chemistry and physical ore characteristics. One of the most critical aspects of the operation is the comminution circuit. With a Bond Ball Mill Work Index of 9.5 kWh/t, the ore is classified as relatively soft to medium hardness; however, the requirement for a 40 μm P80 product necessitates a high power-to-throughput ratio. The grinding circuit’s closed-loop configuration with high-efficiency cyclones allows for precise size control, which is paramount for the subsequent sequential flotation. In this stage, the fine-grained nature of the minerals requires careful reagent dosing to prevent misplaced metals, particularly zinc reporting to the lead concentrate, which can lead to economic penalties.
Sustainability is a core pillar of the Lexindin (H Zone) operation. The facility employs a comprehensive water recycling system, aiming to recover over 80% of process water from the thickening and filtration stages. This reduces the project’s reliance on external water sources and minimizes the environmental footprint. Furthermore, the tailings management strategy is highly progressive. By utilizing a significant portion of the tailings for underground cemented backfill, the project reduces the volume of material stored on the surface and enhances the geomechanical stability of the mine workings. This “paste fill” technology not only mitigates the risk of surface contamination but also allows for more efficient extraction of the mineral resource by providing support for adjacent mining blocks.
Looking toward the future, the Lexindin (H Zone) is poised for further optimization through the implementation of advanced process control (APC) and real-time analyzers. On-stream analyzers (OSA) are being integrated into the flotation circuit to provide instantaneous feedback on pulp chemistry and metal grades, allowing operators to adjust reagent dosages dynamically. This is expected to improve recovery rates by 1-2% and reduce reagent consumption. Additionally, exploration continues to define further extensions of the H Zone, with metallurgical testing ongoing to ensure that the existing flowsheet remains compatible with potential variations in ore mineralogy. The project’s commitment to technical excellence and environmental stewardship ensures its continued relevance in a competitive global market.
Source: Lexindin (H Zone)
Source: NI 43-101 Technical Report
This article provides an overview of mineral processing developments based on publicly available technical reports and industry analysis.
