Why do alluvial gold deposits usually need little crushing or grinding?

Alluvial gold deposits typically require little to no crushing or grinding because the gold already exists as discrete, liberated particles within gravel beds and streams. Unlike endogenetic deposits, where gold is finely disseminated within hard rock or sulfide minerals and necessitates extensive comminution to release the metal, alluvial gold has been naturally weathered and separated from its host rock.123

Because these deposits are essentially mixtures of loose mineral particles, they do not require the intensive mechanical crushing stages used for hard rock ores. Instead, the gold is recovered using gravity concentration techniques, such as jigging or tabling, which exploit the high density of gold to separate it from lighter sand and gravel. Any necessary preparation for these materials is minimal, often involving simple processes like using log washers to break up the placer material.123