Orichalcum
Orichalcum or aurichalcum, ὀρείχαλκος is the name of a metal or two different metals.  Old writings from ancient Greece talk about orichalcum and the Romans made coins out of a metal they called orichalcum, but they might not have been the same metal.  People were not sure exactly what it was, until 2015 a shipwreck was found whose cargo contained ingots of orichalcum.