UBC Theses and Dissertations

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UBC Theses and Dissertations

Extracting gold from gravity concentrates using grinding and sieving Clarkson, Gavin


This thesis presents a novel, chemical-free method of extracting Yukon placer gold from various secondary and tertiary gravity middlings. This method exploits the differences in relative malleability rather than density. At a certain point in gravity gold processing, the middling material contains too many high density minerals to be amenable to further gold extraction through gravity separation. Yukon miners only use gravity extraction methods and low grade gold concentrates are stockpiled for later processing through tedious hand picking, which is rarely completed. An 8-inch diameter batch rod mill was field tested throughout the Yukon placer fields to demonstrate a chemical-free extraction alternative which exploits the resistance of gold to grinding and allows the separation of free gold particles from the finer grind products with sieving. Physical assays often indicated recoveries greater than 90% of the contained gold particles on the oversize portion of the screens, while losses reported to the undersize. The gold remaining in the fine and evenly classified loss material is now amenable to gravity processing. Furthermore, this paper reviews the importance of maximizing gold extraction in the modern Yukon placer environment, followed by reviews of gravity based upgrading equipment, the high malleability of gold, the justification for rod mill use over other comminution methods, and finally field testing methodology and preliminary results.

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Attribution-NonCommercial-NoDerivs 2.5 Canada