Gold dredge

A large gold dredge uses a mechanical method to excavate material (sand, gravel, dirt, etc.)

On large gold dredges, the buckets dump the material into a steel rotating cylinder (a specific type of trommel called "the screen") that is sloped downward toward a rubber belt (the stacker) that carries away oversize material (rocks) and dumps the rocks behind the dredge.

The cylinder has many holes in it to allow undersized material (including gold) to fall into a sluice box.

The original methods to perform placer mining involved gold panning, sluice boxes, and rockers.

Massive floating dredges scooped up millions of tons of river gravels, as steam and electrical power became available in the early 1900s.

[2][4] A New Zealand born mining entrepreneur, Charles Lancelot Garland, bought the technology to New South Wales, Australia, launching the first dredge there, in March 1899, resulting in a major revival of the alluvial gold mining industry.

[10] From Australia, in turn, gold dredging technology spread to New Guinea, at the time an Australian territory, in the 1930s.

[14] Large dredges are still operating in several countries of South America (Peru,[15] Brasil, Guyana,[16] Colombia), Asia (Russia, China, Mongolia[17] Papua-New Guinea) and Africa (Sierra Leone).

[21] Small scale suction dredging in rivers and streams remains a controversial land management topic and the subject of much political turmoil.