Noble metal, of a characteristic gold colour, flexible and malleable. It is found in its natural state in primary deposits (of eruptive origin) and secondary deposits (or alluvial deposits) of sedimentary origin, in threads or nuggets mixed in with sand or gravel. Even though for thousands of years it has been appreciated for its inalterability and strength, it melts in aqua regia, chlorine water, bromine water and in solutions of cyanide in the presence of oxygen. For its use in pictorial techniques, see gilding and gold leaf.