Placer deposit

A concentration of valuable, dense minerals formed when flowing water separates them from lighter sediment. Placer deposits accumulate where currents lose enough energy to leave heavy grains behind.

Hydraulic sorting: The separation of sediment grains by differences in how they move through flowing water. It explains how currents separate dense valuable grains from lighter sediment.
Gold: A dense, malleable chemical element with symbol Au and atomic number 79. Its high density, resistance to chemical weathering, and economic value make it a classic placer mineral.
Gold panning: A manual method of separating gold from sediment by swirling water in a shallow pan. Panning exploits the same density sorting that formed gold placers.
Alluvial deposit: Sediment deposited by rivers and streams. Placer deposits commonly form within alluvial sediment where flowing water sorts mineral grains.
Klondike Gold Rush: A gold rush to Canada's Yukon Territory that began in 1896. Many prospectors sought placer gold in Klondike creeks and river gravels.
Settling velocity: The speed at which a particle falls through a fluid under specified conditions. Dense grains settle faster than similarly sized light grains, enabling placer concentration.
Cassiterite: The mineral tin oxide, SnO₂, and the principal ore of tin. Its density and durability allow it to accumulate in stream and coastal placers.
Hydraulic mining: A mining method that uses high-pressure water jets to dislodge and transport sediment. It was used to mine extensive placer gravels, especially during the California Gold Rush.
Eluvial deposit: A mineral concentration formed by weathering and gravity near its source, with little transport. It contrasts with placers formed after water transports and sorts mineral grains.
Gold mining: The extraction of gold from geological deposits. Placer working is one of the principal methods within the broader history of gold mining.

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