The Golden Fleece of legend, sought by the Argonauts, was probably a sheepskin that had been similarly employed. Gold amalgamates with mercury on contact. Further, mercury is strongly attracted to itself. These properties are joined in the amalgamation process. First, ore is finely ground to free the gold mechanically from the gangue.
Water is added to form a pulp.
Then mercury is added to the pulp, and the fluid is passed over mercury-coated copper plates. The mercury unites with the gold in the pulp, and the amalgam adheres to the plates. At intervals the accumulation is removed. Mercury was often placed behind the riffles in sluices to improve gold collection. The cyanide process, invented near the end of the 19th century, was first employed to treat the gangue, or tailings, from amalgamation plants.