Lead
Lead is a metal that alchemists used as prima materia—that is, the insignificant metal that is to be transformed into gold. It is a black, “worthless” metal; “the most opaque substance there is.” (Aion, par. 215.) (This is in contrast to mercury.) However, “the philosophers’ lead” contains “the shining white dove,” which is also called the salt of metals; and the most opaque metal can be transformed into a transparent gemstone.
The metal is associated with Saturn, which in many contexts has a depressing and tyrannical quality. Paracelsus wrote: “If alchemists knew what Saturn contains, they would abandon all other materials and devote their work exclusively to this metal.” (Quoted in Chevalier 1996.)