During the erosive cycle, the heavier and more durable gold is concentrated into rich deposits, even though the original rock may have contained low values. Residual deposits of gold are found close to the gold bearing outcrop after the other rock fragments have weathered and been carried away. Alluvial deposits are formed by the concentration of gold particles within stream systems, under the action of running water. Beach placers , where gold is concentrated in beach sands by wave action, are a type of alluvial deposit. Leads are former stream courses, containing gold, where barren sands have covered the original passage of the stream.
Deep leads are gold deposits in former stream beds which have been covered with basaltic lava.
Nuggets are formed, either as rich fragments of primary deposits which have been transported and deposited in a sedimentary environment, or a chemical accretion of small gold particles into larger fragments. Some nuggets may have formed through the chemical action of host soils or sediments on a gold solution. 1063 degrees Celsius. Very high can be drawn into a thin wire without breaking. Although the international gold standard backing trading nation currencies was abandoned in 1971, gold still remains an important part of official asset reserves.