Guanin is the name given to a metal alloy with a high gold content found in West Africa that some see as the explanation for Plato’s reference to the mysterious orichalcum. It is interesting that the when Columbus arrived in the Caribbean the natives displayed spears tipped with a yellow metal which they called guanin. On his return to Spain these were shown to be of the same composition as artefacts from Guinea in West Africa(a).
A paper(b) by Ana María Falchetti, in which she discusses copper based alloys in pre-Columbian America, should be read in connection with this subject.
*(b) http://www.humanas.unal.edu.co/colantropos/files/5414/7422/2423/The_seed_of_life__Falchetti.pdf *