" move to BFS is a fait bit more metallurgical work..."
The Hillgrove gold mine in New South Wales, Australia, has faced several metallurgical challenges over its operational history. These challenges have affected the efficiency of gold and antimony recovery and have required specialized processing techniques to optimize extraction. Some of the key metallurgical challenges include:
1. Complex Ore Mineralogy
The Hillgrove ore contains a mix of gold and antimony minerals, primarily stibnite (antimony sulfide) and arsenopyrite (arsenic sulfide). The presence of both gold and antimony in the same ore complicates the processing, as each mineral requires different conditions for optimal recovery. This complexity often results in lower recovery rates for both gold and antimony if not managed properly.
2. Refractory Nature of the Ore
A significant portion of the gold at Hillgrove is found in association with sulfide minerals, making it refractory. Refractory gold ores are resistant to standard cyanide leaching because the gold is encapsulated in sulfide minerals or forms solid solutions with them. This necessitates additional processing steps, such as flotation, roasting, pressure oxidation, or bio-oxidation, to liberate the gold before it can be recovered.
3. Fine Gold Particles
The gold at Hillgrove is often found in very fine particles, which can be difficult to recover using conventional gravity or flotation methods. Fine particle gold is more challenging to concentrate and can result in lower recovery rates unless specialized processing techniques are employed.
4. Antimony Interference
The presence of antimony, primarily in the form of stibnite, poses challenges for gold recovery. Stibnite can interfere with the cyanidation process, as antimony reacts with cyanide, reducing its availability for gold dissolution and leading to higher cyanide consumption. Additionally, antimony can form stable complexes with gold, making it harder to separate the two.
5. Arsenic Management
Arsenopyrite, a common sulfide mineral at Hillgrove, contains arsenic, which poses environmental and metallurgical challenges. Arsenic must be carefully managed to prevent environmental contamination and to comply with safety regulations. The treatment of arsenopyrite requires additional processing steps to remove or stabilize arsenic before it can be safely disposed of or used in other processes.
6. Oxidation and Roasting Requirements
To address the refractory nature of the ore, oxidation processes such as roasting or pressure oxidation may be required. These processes are costly and energy-intensive, and they need careful control to prevent the release of harmful gases like sulfur dioxide and arsenic trioxide.
7. Tailings Management
The processing of complex ores generates tailings that may contain residual gold, antimony, arsenic, and other potentially harmful substances. Effective tailings management is essential to prevent environmental contamination and to meet regulatory standards.
These metallurgical challenges have required Hillgrove operators, including Straits Resources and later Red River Resources, to invest in specialized processing facilities and develop tailored metallurgical processes to optimize the recovery of both gold and antimony while minimizing environmental impact.
LRV Price at posting:
40.0¢ Sentiment: None Disclosure: Not Held
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