Overview
The D31 mineral processing facility, technically identified within the framework of the Cordero Silver Project development in Chihuahua, Mexico, represents one of the most significant silver-lead-zinc-gold processing operations currently in the development pipeline. Managed by Discovery Silver Corp., the project is situated in the prolific Silver Belt of Mexico, a region renowned for its world-class carbonate replacement deposits and epithermal systems. The D31 project is defined by its massive scale and a multi-phased expansion strategy designed to optimize capital efficiency while maximizing the recovery of silver, lead, and zinc concentrates. The strategic importance of the D31 mine lies not only in its significant silver reserves—placing it among the largest undeveloped silver resources globally—but also in its sophisticated metallurgical approach to processing complex, polymetallic ores.
Located approximately 35 kilometers northeast of the city of Parral, the project benefits from excellent existing infrastructure, including proximity to power grids, roads, and a skilled mining labor force. The processing philosophy for the D31 mine involves a phased approach, starting with a robust initial throughput that doubles in subsequent years to capture economies of scale. Phase 1 is engineered for a throughput of 25.5 kilotonnes per day (kt/d), specifically targeting higher-grade starter zones to ensure rapid capital payback. As the operation matures, Phase 2 and 3 expansion will see this capacity increase to a nominal 51.0 kt/d. This scale of operation necessitates a highly efficient comminution and flotation circuit, leveraging modern automation and large-scale equipment to maintain competitive operating costs in a fluctuating global metal market.
Key Process Stages
The D31 mineral processing flowsheet is a refined polymetallic circuit optimized for the sequential recovery of lead and zinc concentrates, with silver reporting primarily to the lead concentrate. The following stages represent the core of the processing operations:
- Primary Crushing: The Run-of-Mine (ROM) ore is reduced in size using a large-scale primary gyratory or jaw crusher. The design considers a primary crushing availability of 75%, ensuring a consistent feed to the downstream grinding circuits despite the mechanical demands of high-tonnage throughput.
- Grinding and Comminution: The circuit utilizes a standard SAG (Semi-Autogenous Grinding) and Ball Mill configuration (SABC) to achieve the target grind size. The grinding and flotation section is designed with a high operational availability of 91.3%, reflecting the robust nature of the equipment selection.
- Lead Flotation: The ground slurry enters the lead flotation circuit first. This stage uses specialized collectors and depressants to selectively float galena (lead sulfide) while depressing zinc and iron sulfides. Silver is highly associated with the lead and is recovered here as a high-value lead-silver concentrate.
- Zinc Flotation: Following lead recovery, the tailings are conditioned to activate sphalerite (zinc sulfide). The zinc flotation circuit produces a separate zinc concentrate. Phase 3 of the project specifically includes an expansion of the zinc cleaning circuit to handle higher feed grades as the mine matures.
- Concentrate Dewatering: Both lead and zinc concentrates undergo thickening and filtration. The filtration circuit is designed for 82.2% availability, producing a dry filter cake suitable for transport to smelters.
- Tailings Management: Process tailings are managed through thickening and subsequent storage, with a focus on maximizing water recovery for reuse within the plant, a critical factor in the semi-arid climate of Chihuahua.
Critical Data
The technical performance of the D31 circuit is governed by rigorous design criteria focused on throughput stability and metallurgical recovery. The following table summarizes the key operational parameters derived from recent feasibility analysis:
| Parameter | Value | Unit |
|---|---|---|
| Phase 1 Throughput Rate | 25.5 | kt/d |
| Phase 2 & 3 Throughput Rate | 51.0 | kt/d |
| Primary Crushing Availability | 75.0 | % |
| Grinding and Flotation Availability | 91.3 | % |
| Concentrate Filtration Availability | 82.2 | % |
| Primary Grind Size (P80) | Variable (150-200) | µm |
| Estimated Mine Life | 15+ | Years |
| Target Concentrate – Silver | High-Grade | g/t |
Technical Details and Sustainability
The technical sophistication of the D31 mine is most evident in its approach to metallurgical variability and sustainability. Polymetallic deposits often present challenges due to the intergrowth of minerals; however, the D31 circuit addresses this through a robust sequential flotation regime. By prioritizing lead flotation in the first stage, the plant maximizes silver recovery, as silver at Cordero is predominantly hosted within the lead-bearing minerals. The expansion in Phase 3 is a strategic response to the geological model, which predicts an increase in zinc grades in later years of the mine life. This “future-proofing” of the zinc cleaning and dewatering circuits ensures that the project can maintain high recoveries even as the ore characteristics evolve over time.
Sustainability is a core pillar of the D31 project design. Water management is the primary environmental consideration, given the project’s location. The facility incorporates high-capacity thickeners for both concentrates and tailings to reclaim as much process water as possible. By recirculating water from the tailings storage facility (TSF) back to the grinding circuit, the D31 operation significantly reduces its reliance on fresh groundwater sources. Furthermore, the selection of energy-efficient grinding technology, such as large-scale variable speed drives for the mills, helps minimize the carbon footprint of the operation. The use of high-efficiency flotation cells also reduces the overall reagent consumption per tonne of ore processed, aligning the project with modern ESG (Environmental, Social, and Governance) standards.
The future outlook for the D31 mine is centered on the potential for further resource expansion and process optimization. The current phased approach allows the operator to refine the metallurgical parameters during Phase 1, applying “lessons learned” to the much larger Phase 2 expansion. This iterative approach to processing design reduces technical risk and provides a clearer path to achieving nameplate capacity. As Discovery Silver continues to de-risk the project through advanced engineering and community engagement, the D31 circuit stands as a benchmark for large-scale, efficient, and sustainable silver production in the 21st century. The integration of advanced automation and real-time monitoring within the flotation circuit is expected to further enhance recoveries and provide a stable supply of critical metals to global markets for decades to come.
Source: D31 | Reports_256 (Cordero Silver Project)
Source: NI 43-101 Technical Report
This article provides an overview of mineral processing developments based on publicly available technical reports and industry analysis.
