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How are endogenetic gold deposits processed differently from alluvial deposits?

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A worker in safety gear walks beside a conveyor belt carrying ore at the Tanami gold mine in the arid, expansive landscape of the Tanami Desert. — gold processing The Tanami gold mine, Northern Territory, Australia.

The processing of gold depends heavily on the nature of the deposit. Alluvial and endogenetic deposits require distinct approaches due to the physical state of the gold within them.

Alluvial Deposits

Alluvial deposits consist of unconsolidated material where gold is typically found in its elemental form. Because these deposits require little to no comminution (crushing or grinding), they are primarily processed using gravity concentration techniques. Methods such as jigging, tabling, or traditional placer mining exploit the high density of gold, allowing lighter sand and gravel to be washed away while the denser gold particles are retained.12

Endogenetic Deposits

Endogenetic deposits, which form within the Earth, often contain gold that is finely disseminated within sulfide minerals. Processing these deposits is more complex:13
* Comminution: The ore must first be crushed and ground to liberate the gold particles.1
* Gravity Separation: This is often used as a preliminary step to recover coarse, native gold particles.1
* Froth Flotation: Because the remaining gold is often too finely dispersed for traditional methods, froth flotation is employed to concentrate the sulfide mineral fraction containing the gold for further extraction.13