In
geology, a
placer deposit or
placer is an accumulation of valuable minerals formed by gravity separation during sedimentary processes. The name is from the
Spanish word
placer, meaning "
alluvial sand".
Placer mining is an important source of
gold, and was the main technique used in the early years of many gold rushes, including the
California Gold Rush. Types of placer deposits include
alluvium,
eluvium, beach placers, and paleoplacers.