heavy metal, a metallic element with a specific gravity five or more times that of water. The heavy metals include antimony, arsenic, bismuth, cadmium, cerium, chromium, cobalt, copper, gallium, gold, iron, lead, manganese, mercury, nickel, platinum, silver, tellurium, thallium, tin, uranium, vanadium, and zinc. Small amounts of many of these elements are common and necessary in the diet. Large amounts of any of them may cause poisoning.
