An
alluvial deposit is an accumulation of a valuable
ore,
gemstones, or simply
gravel or
clay in the bed or former bed of a
river. Valuable materials such as
gold may be extracted using techniques of
placer mining[?]. Gems historically were found in the gravels of
India particularly
diamonds and continue to be mined from alluvium in
Myanmar and
Sri Lanka.
Glaciers may also deposit alluvium known as
till.
See also: list of minerals