The Welcome Stranger is the biggest alluvial gold nugget that has ever been found, which had a calculated refined weight of 97.14 kilograms (3,123 ozt). It measured 61 by 31 cm (24 by 12 in) and was discovered by prospectors John Deason and Richard Oates on 5 February 1869 at Moliagul, Victoria, Australia, about 14.6 kilometres (9 miles) north-west of Dunolly.

Alluvium (from the Latin alluvius, from alluere, "to wash against") is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluvium is also sometimes called alluvial deposit. Alluvium is typically geologically young and is not consolidated into solid rock. Sediments deposited underwater, in seas, estuaries, lakes, or ponds, are not described as alluvium.Floodplain alluvium can be highly fertile, and supported some of the earliest human civilizations.