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26/06 - Gold in the ‘Mundic’: The Saga of Dargue’s Reef, Majors Creek

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Looking for photos of the early operations at Dargue's reef and I am sure there must have been some taken, particularly of the chlorination plant. If you come across any please let me know.

 

Thanks Cheers Ken
 

 

From : Journal of Australasian Mining History, Vol. 12, 2014

BY KEN MCQUEEN IAE, University of Canberra

Gold is found in bedrock reefs and lodes, generally in its elemental form, as well as in secondary deposits formed by weathering and erosion of these primary occurrences (for example, alluvial gold). After quartz, the mineral most commonly associated with gold is pyrite (iron sulphide) also known colloquially as ‘fools gold’ or ‘mundic’. This association has guided prospectors to new lode gold deposits, but also plagued attempts to extract the gold where the two minerals are rather too intimately associated. In these refractory ores the gold is commonly locked in the pyrite as small, in some cases sub-microscopic, inclusions or even dissolved in the pyrite host. Up until the end of the nineteenth century refractory gold ores, including those at such famous deposits as the Golden Mile, Kalgoorlie, and some of the ores on the Witwatersrand in South Africa, posed a major challenge to metallurgists. In many cases, some gold could be released by fine grinding, but a significant proportion was lost with the pyrite in the tailings. Various methods of roasting and chemical treatment, particularly using chlorination and cyanidation, were ultimately developed to recover this ‘lost’ gold.1

Dargue’s Reef, near Majors Creek in southern New South Wales (Fig. 1), is a pyritic gold deposit and the history of its mining and exploitation highlight some of the challenges and developments in extracting gold from the ‘mundic’. The deposit was discovered in 1868 by Joseph Dargue while he was mining alluvial gold in Spring Creek and it is still the largest known bedrock gold deposit in the Majors Creek area. Natural surface weathering had broken down the pyrite in the upper part of the deposit to release its contained gold. Much of the fine alluvial gold in the Majors Creek and surrounding goldfields of Jembaicumbene, Bells Creek and Araluen was probably derived from the weathering and oxidation of similar pyritic bedrock deposits.2 Within the upper oxidised zone it was relatively easy to extract the free gold by gravity separation or grinding of consolidated material and mercury amalgamation, but below this zone the difficulties of extracting gold from the unweathered ‘mundic’ soon became apparent. Over the next 140 years numerous attempts were made to profitably work the ‘mundic’ at Dargue’s Reef. All failed, although not just because of the metallurgical difficulties. Modern gold extraction methods can effectively treat pyritic ores and now a new attempt is being made to mine Dargue’s Reef. An extensive drilling program has indicated a viable resource and against some local opposition, approval has been granted to establish an underground mine. A new chapter in the history of Dargue’s Reef may be beginning. 

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