Seven Planets of the Week and Seven Alchemical Metals.

From antiquity up until the mid-eighteenth century, the number of metals known and recognized as such was seven. They were: lead, tin, iron, gold, copper, mercury and silver. Belief in a linkage of these seven metals with the seven Planets reaches back into prehistory: there was no age in which silver was not associated with the Moon, nor gold with the Sun. These links defined the identities of the metals. Iron, used always for instruments of war, was associated with Mars, the soft, pliable metal copper was linked with Venus, and the chameleon metal mercury had the same name as its planet. Then, around the beginning of the 18th century these old, cosmic imaginations were swept away by the emerging science of chemistry. The characters of the metals were no longer explained in terms of their cosmic origins but instead in terms of an underlying atomic structure.