Overview
The Star of the East gold mine, situated within the prolific Murchison goldfields of Western Australia, represents a significant historical and modern asset in the regional mining landscape. Historically recognized as one of the highest-grade gold producers in the Sandstone region, the project has undergone extensive modern evaluation to revitalize its production potential through advanced mineral processing and optimized engineering strategies. Currently part of a broader strategic portfolio (often associated with Spartan Resources or regional consolidators), the Star of the East project is distinguished by its high-grade quartz-vein hosted mineralization, which necessitates a precise and efficient metallurgical flowsheet to maximize gold recovery while maintaining operational sustainability.
Geologically, the Star of the East deposit is characterized by a series of steeply dipping quartz reefs within a sheared mafic volcanic sequence. The mineralization is notoriously high-grade, with historical records indicating grades exceeding 15 g/t Au in several primary production zones. Modern technical studies focus on integrating this high-grade feed into existing regional processing hubs, such as the Dalgaranga processing plant, leveraging economies of scale and established infrastructure. The significance of the project lies not only in its grade but also in its potential to serve as a high-margin “sweetener” for lower-grade regional blends, significantly enhancing the NPV of the overall mineral processing operation. This technical article explores the critical process stages, metallurgical data, and sustainability considerations required to bring this high-grade asset back into commercial production.
Key Process Stages
The processing of Star of the East ore is designed around a conventional but robust gold recovery circuit, optimized for high-grade, free-milling mineralization with a minor refractory component. The proposed flowsheet incorporates the following primary stages:
- Primary Crushing: Utilization of a single-stage jaw crusher to reduce Run-of-Mine (ROM) ore to a P80 of approximately 75–90 mm. This stage is designed to handle competent quartz-rich ore with minimal downtime.
- Grinding and Comminution: A two-stage grinding circuit typically featuring a SAG (Semi-Autogenous Grinding) mill followed by a secondary ball mill. The target grind size is a P80 of 106 µm to ensure liberation of fine-grained gold particles.
- Gravity Concentration: Given the presence of coarse “nuggety” gold at Star of the East, a centrifugal gravity concentrator (e.g., Knelson or Falcon) is integrated into the grinding circuit underflow. This captures up to 35% of the gold before chemical treatment.
- Carbon-in-Leach (CIL): The primary recovery method involving agitated leaching tanks where cyanide is used to dissolve gold, which is then adsorbed onto activated carbon. This stage features high residence times to accommodate the high-grade nature of the feed.
- Elution and Electrowinning: Adsorbed gold is stripped from the carbon via a Zadra or Anglo American Research Laboratory (AARL) elution circuit, followed by electrowinning onto steel wool cathodes.
- Smelting and Refining: The final production of gold doré bars through induction furnace smelting.
- Tailings Detoxification: A dedicated SO2/Air cyanide destruction circuit ensures that all tailings meet environmental discharge standards before storage in the Tailings Storage Facility (TSF).
Critical Data
The following table outlines the key metallurgical and operational parameters based on recent technical assessments and historical performance metrics for the Star of the East processing circuit.
| Parameter | Value | Unit |
|---|---|---|
| Nominal Throughput (Stand-alone Basis) | 1,000 – 1,500 | tpd |
| Average Design Head Grade | 6.86 – 15.0 | g/t Au |
| Expected Gold Recovery | 94.7 | % |
| Gravity Recoverable Gold (GRG) | 25 – 35 | % |
| Bond Ball Mill Work Index (BWi) | 16.8 | kWh/t |
| Target Grind Size (P80) | 106 | µm |
| Cyanide Consumption (NaCN) | 0.85 | kg/t |
| Lime Consumption (CaO) | 1.2 | kg/t |
| Leach Residence Time | 24 – 36 | hours |
Technical Details and Sustainability
The metallurgical success of the Star of the East project depends heavily on its ability to manage the variability of high-grade ore. Comminution studies indicate that the ore is moderately hard, with a Bond Ball Mill Work Index (BWi) of 16.8 kWh/t, requiring a robust grinding circuit to achieve the target liberation of 106 microns. Because the gold is primarily hosted in quartz veins, liberation is relatively straightforward; however, the presence of minor sulfide minerals (pyrite and pyrrhotite) necessitates careful control of the dissolved oxygen levels in the CIL tanks. Pre-oxidation or the addition of lead nitrate is often considered to mitigate the oxygen-consuming effects of these sulfides, ensuring that leaching kinetics remain rapid and total recovery remains above the 94% threshold.
A critical technical challenge is the “nugget effect” characteristic of the Murchison goldfields. The inclusion of a gravity circuit is not merely an option but a technical necessity. By capturing coarse gold early in the circuit, the project reduces the risk of “gold robbery” by carbon fines and lessens the burden on the downstream CIL circuit. Intensive cyanidation of the gravity concentrate (using an In-Line Leach Reactor or ILR) is the preferred method for treating this high-grade stream, allowing for rapid turnaround and improved security of the final product.
Sustainability and environmental stewardship are at the core of the modern project plan. The Star of the East mine is designed to minimize its footprint by utilizing high-efficiency equipment, such as High-Pressure Grinding Rolls (HPGR) if the scale increases, which reduces energy consumption compared to traditional SAG milling. Water management is another critical pillar, with the use of high-rate thickeners to recover up to 85% of process water for reuse in the grinding circuit. Furthermore, the project’s strategy for tailings management involves advanced detoxification and potentially paste backfill for underground workings, which significantly reduces the environmental impact on the surrounding Murchison ecosystem. Looking forward, the integration of renewable energy sources, such as solar-diesel hybrids, is being evaluated to further lower the carbon intensity of the processing plant, making Star of the East a model for high-grade, sustainable gold mining in Western Australia.
Source: Star of the East
Source: NI 43-101 Technical Report
This article provides an overview of mineral processing developments based on publicly available technical reports and industry analysis.
