The specific gravity of gold is 19.3, which means that gold is 19.3 times heavier than an equal volume of water. The greater density of gold also leads to its concentration in nature as a placer deposit. Obviously as a recreational miner, our level of economic importance is much lower than company who have to turn a profit. Generally, placer deposits form as heavy, robust minerals are freed from the parent rock through erosion and weathering and then are transported, sorted and collected into workable deposits by the action of water. There are several types of placer deposits.
Eluvial deposits are placers that are found close to the parent rock.
Thus free gold found in the ground on a hillside below the outcrop of a gold-bearing vein is eluvial. Alluvial deposits are the broad term applied to placers formed by the mechanical action of moving water of streams, lakes, or oceans. One can tell how close the alluvial deposits is to the source vein by the appearance of the gold. As gold is trasported, the flakes become rounded and flat. Therfore, the more angular the gold flakes, the closer the deposit is to the original source.