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Why does gold's high density make gravity concentration effective?
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gold processing
The Tanami gold mine, Northern Territory, Australia.
Gravity concentration is highly effective for gold processing because it exploits the significant difference in density between gold particles and the surrounding waste material, or gangue.1
In various gravity separation methods, this physical property allows for efficient mechanical sorting:
- Jigging: By pulsing a water stream through a bed of material, the oscillating motion causes the mixture to stratify by density. The heavy gold particles settle into the lowest layer, while lighter sand and gravel are carried away.12
- Tabling: Using grooved or ridged tables, a slurry is passed over an inclined surface. The denser gold particles are retained by the table's features, while the less dense materials are washed away by the flow of water.12
- Spirals: As ore pulp flows down a spiral channel, the higher density of gold causes the particles to concentrate toward the inner side of the stream, where they can be systematically removed.1
Because gold is significantly denser than the sand, gravel, or other minerals typically found in alluvial deposits or crushed ore, gravity techniques provide a simple and cost-effective way to recover coarse gold particles.12