Overview
The Ruby No. 3 mine, a pivotal claim within the broader Three Hills Mine and Hasbrouck Gold Project, represents a significant development in the mining landscape of Esmeralda County, Nevada. Situated in a region with a storied history of precious metals extraction, the Ruby No. 3 claim is part of an integrated operation managed under the Hasbrouck Project’s phased development strategy. This project is characterized by its dual-deposit approach, consisting of the Three Hills Mine and the Hasbrouck Mine, located approximately five miles apart. The Ruby No. 3 claim itself is strategically positioned within the Three Hills deposit, which is slated for the first phase of production due to its amenability to cost-effective processing techniques.
The significance of the Ruby No. 3 mine lies in its technical simplicity and economic viability. Operating as a Run-of-Mine (ROM) heap leach facility, the project bypasses the intensive energy requirements of traditional milling and grinding for its initial phase. This approach is particularly advantageous given the metallurgical characteristics of the ore found within the Ruby No. 3 and surrounding claims. The project is designed to produce significant gold yields with relatively low capital intensity, a critical factor in the current economic climate for junior and mid-tier mining operations. By leveraging Nevada’s favorable mining jurisdiction and existing infrastructure, the Ruby No. 3 mine is poised to become a key contributor to the regional gold supply, utilizing advanced cyanide leaching and carbon adsorption technologies to maximize recovery while maintaining a minimal environmental footprint.
From a corporate and strategic perspective, the development of Ruby No. 3 is the cornerstone of the Hasbrouck Project’s cash flow model. The project utilizes a conservative metal price assumption of $1,790 per ounce of gold, ensuring that the mineral processing circuit remains robust even amidst market volatility. As the first stage of a multi-decade mining plan, the successful commissioning of the mineral processing circuit at this site will set the technical precedent for the subsequent, more complex processing stages planned for the Hasbrouck deposit.
Key Process Stages
The mineral processing circuit for the Ruby No. 3 and Three Hills Mine is engineered for high-volume efficiency with a focus on maximizing gold recovery from oxidized ores. The following stages outline the flow of material from the pit to the final doré production:
- Run-of-Mine (ROM) Delivery: Ore is extracted via conventional open-pit mining methods. Unlike many hard-rock operations, the ore from the Ruby No. 3 claim is delivered directly from the pit to the heap leach pad without primary or secondary crushing, significantly reducing operational costs.
- Heap Stacking: The ROM ore is stacked onto a single-use, engineered geomembrane liner system. The stacking process is carefully managed to ensure optimal permeability and to prevent the compaction of “fines” that could inhibit solution flow.
- Cyanide Leaching: A dilute alkaline cyanide solution is applied to the top of the heap using a network of drip emitters or sprinklers. This “lixiviant” percolates through the ore, selectively dissolving gold and silver from the host rock.
- Solution Collection (Pregnant Leach Solution): The gold-bearing solution, known as Pregnant Leach Solution (PLS), is collected at the base of the heap via a system of perforated pipes and channeled to a central pregnant solution pond.
- Carbon Adsorption (ADR Circuit): The PLS is pumped through a series of carbon adsorption columns. Here, the dissolved gold is adsorbed onto the surface of activated coconut-shell carbon. The remaining “barren” solution is then refortified with cyanide and recirculated back to the heap.
- Toll Stripping and Refining: Once the carbon is fully “loaded” with gold, it is removed from the circuit. Under the current project design, the loaded carbon is transported to an off-site facility for stripping (elution) and refining into doré bars. This arrangement reduces the on-site capital requirements for an elution plant and refinery.
Critical Data
The following technical parameters define the operational capacity and metallurgical performance of the Ruby No. 3 mineral processing circuit within the Three Hills Mine framework.
| Parameter | Value | Unit |
|---|---|---|
| Design Throughput (Three Hills ROM) | 15,000 | Tons per Day (TPD) |
| Design Throughput (Hasbrouck Crushed) | 17,500 | Tons per Day (TPD) |
| Gold Cut-off Grade (Three Hills) | 0.005 | oz Au/ton |
| Operating Days per Year | 365 | Days |
| Estimated Life-of-Mine Capital Cost | 222 | Million USD |
| Average Operating Cost (Adjusted) | 10.02 | USD/ton ore |
| Projected Gold Price (Base Case) | 1,790 | USD/oz |
| Projected Silver Price (Base Case) | 22.50 | USD/oz |
| Stacking Method | Truck/Loader Stacking | Method |
Technical Details and Sustainability
The technical architecture of the Ruby No. 3 mine’s processing circuit is a testament to modern heap leach optimization. A primary technical challenge addressed in the project design is the management of ore permeability. Since the Three Hills operation utilizes ROM leaching—meaning the ore is not crushed—the natural fragmentation achieved through drilling and blasting is critical. Metallurgical studies indicated that the gold deportment is largely associated with fractures and brecciated zones within the orebody. Consequently, the blast patterns are engineered not just for volume but for “fracture-optimization,” ensuring that the cyanide solution can access the gold without the need for mechanical comminution. This reduces the project’s overall power consumption, making it significantly more energy-efficient than traditional mill-and-float circuits.
Sustainability is integrated into the core of the Ruby No. 3 processing strategy. The use of a single-use leach pad system is a proactive measure for environmental reclamation. Once a section of the pad is fully leached, it can be rinsed and reclaimed in place, reducing the long-term footprint of the operation compared to multi-lift permanent pads. Furthermore, the water management system is designed as a closed-loop circuit. All solutions are contained within lined ponds and piping systems, with zero discharge to the surrounding environment. In the arid climate of Esmeralda County, water conservation is paramount; the project employs advanced evaporation-control measures on the ponds to minimize water loss.
Future technical outlooks for the project involve the integration of the Hasbrouck Mine deposit, which will introduce a more advanced crushing circuit. This expansion will include three stages of crushing: a primary jaw crusher, two secondary cone crushers, and a High-Pressure Grinding Roll (HPGR) unit. The HPGR technology is a critical addition for the Hasbrouck deposit as it creates micro-fractures in the ore particles, which enhances leach kinetics and improves overall recovery rates for silver and gold. Additionally, the use of a pug mill for agglomeration with cement will be employed at the Hasbrouck stage to ensure that the “cake” produced by the HPGR does not impede solution flow.
One of the unique risks identified and mitigated in the technical planning for Ruby No. 3 is the variability of gold recovery based on the blasting efficiency. To mitigate the risk of lower-than-expected recoveries from ROM ore, the project management team has implemented a rigorous variability testing program. This program continuously samples different zones of the Ruby No. 3 claim to calibrate the cyanide concentration and application rates. By adjusting the chemical parameters of the lixiviant in real-time based on the specific mineralogy of the current ore lift, the operation maintains a steady recovery curve. This level of technical oversight ensures that the Ruby No. 3 mine remains a high-margin asset throughout its operational life, providing a stable foundation for the future growth of the Hasbrouck Gold Project.
Source: Ruby No. 3 | Hasbrouck Project Technical Reports
Source: NI 43-101 Technical Report
This article provides an overview of mineral processing developments based on publicly available technical reports and industry analysis.
