Historians can only speculate on how metals were first discovered and worked. Since most metals must be softened by heat in order to be extracted from their ores, campfires and hearths may have been where metals were initially observed and subjected to experimentation. Some observant individual might have noticed that rocks near the heat softened and rehardened. Eventually, someone learned to manipulate the metal ore and searched for ways to obtain more of the new material. The same act of discovery of any single metal may have been repeated in different parts of the world.

Simultaneous discoveries in metallurgy occurred in more recent times with such inventors as William Kelly and Sir Henry Bessemer, the Siemens brothers and Pierre-Emile Martin; and Charles Martin Hall and Paul-Louis-Toussaint Héroult. It seems reasonable to suppose similar multiple discoveries occurred even more often in prehistory or early historical...