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Editorial: Eldorado dredge part of town's history
A MARVEL of its time it may have been but the Cock’s Eldorado gold dredge had a profound effect on the local community.
Built in 1936, the behemoth weighed about 2000 tonnes, making it the largest floating dredge in the Southern Hemisphere.
Witnesses said the machine dominated the town, running seven days a week, creating a noise which could be heard 20 kilometres away.
At the time the state-of-the-art dredge was the largest constructed in Australia, made by Thompson’s Engineering and Pipe Company in Castlemaine.
Its inception was brought about when the price of gold more than doubled in the early 1930s, creating a strong incentive to mine deeply buried gold.
The dredge was built in an old mining paddock left by the hydraulic sluicing plant of the earlier Cock’s pioneer mine.
It was 64 metres long, 20 metres wide at the stern and 50 metres wide at the bow.
A conveyor belt carried 118 buckets, each weighing 1.4 tonnes, which took the raw earth into the body of the dredge for processing.
Running on electricity, it was the third largest user of power in Victoria after the cities of Melbourne and Geelong.
Using 14 motors of varying capacity, the dredge required 900 horsepower to operate.
Dirt was lifted 30 metres from the bottom of the lake the dredge created as it was winched along by two cables fixed to the land on either side.
The raw earth was processed through a revolving tumbler containing thousands of small holes to separate the larger stones from the sand and clay that contained the gold.
Sand and clay were tipped into vibrating jigs to separate the heavier material, with the gold then extracted through amalgamation with mercury.
Tin was recovered with a magnetic separator.
It operated until 1954, producing 70,000 ounces of gold — valued at about $28 million in today’s values.
The dredge was listed on the State Register of Historic Buildings and the National Estate Register in 1975.