Alluvial Gold Mining
Alluvial gold deposits form over time where a river runs, or has previously run through ground which is rich in gold. The erosive power of the water removes the surrounding rock due to its comparative low density while the heavier gold resists being moved. Alluvial gold usually takes the form of dust, thin flakes or nuggets.
The first stage in alluvial gold mining is to take the dredged river bed material and separate the small sand faction (where the gold is found) from the larger mineral fraction. In a typical alluvial mining process physical separation methods such as screening and gravity separation are employed to separate the gold from the mineral fraction.