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How does a sluice box trap gold-bearing material?
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mining
Typical development workings of an underground mine.
A sluice box is a rectangular, inclined trough used in placer mining to recover heavy minerals like gold from alluvial deposits.12
The device traps gold-bearing material through the following process:
- Gravity Separation: The method relies on the high density of gold compared to lighter siliceous waste materials.2
- Water Flow: A mixture of water and placer dirt is introduced at the upper end of the inclined box. As the slurry flows downward, the water transports the lighter material while allowing the heavier gold to sink.12
- Riffle Action: The bottom of the sluice is lined with riffles—transverse bars made of wood, stone, iron, or rubber. These riffles agitate the current and create small basins or eddies that retard the water's flow.12
- Retention: By slowing the current, these basins allow the dense gold particles to settle and be trapped behind the baffles, while the lighter waste matter is washed away by the stream.32