The process of alluvial mining involves digging and sifting through mud, sand and gravel using shovels, sieves, or even bare hands. Typically, gold, diamonds, and sapphires come from specific geologic rock formations. These rock formations have evolved over millions of years and are continuing to evolve. Over time the land is eroded by rivers and streams, which is when the alluvial minerals are brought to the surface, deposited, into the sediments.
The minerals are carried by those streams farther downstream from the original source rocks. These deposits are called alluvial deposits. The locations of any alluvial deposit is controlled by the surrounding topography, drainage patterns, and some impact from previous mining efforts. Alluvial deposits are often mined and exploited by small-scale miners using artisanal mining techniques.