From Greek words Oros (mountain) and chalcos (copper), which means "obsidian" (a kind of stone that used to be a cash-equivalent at that time and was replaced by the spondylus shell around 5500 BC.). Moreover, it is a legendary metal described by Plato. According to him, it was used by Atlanteans for its mysterious power. The word Greek has a number of meanings relating to Greece, including: Architecture of Ancient Greece Art in Ancient Greece Greek alphabet Greek colonies Cuisine of Greece Greek salad Ethnic Greek Greco-Turkish relations Greece The Greek People Greek-Americans History of Greece History of Mycenaean Greece History of Ancient... Species many; for examples see text Spondylus is a genus of bivalve mollusks, the only genus in the family Spondylidae. ... Statue of a philosopher, presumely Plato, in Delphi. ...
In Greek the root "püro" was used to denominate to the "same fire" and all the resemblance and derivative.
As it demonstrates it in another fragment of the dialogue of Kritias, where it clarifies that the "oreichalcos" or "mountain copper" were obtained directly from mosntañas.
So, based upon the etymology of the Greek word "oreichalcos" we should conclude that Plato was referring to one of the two meanings found above - either "mountain copper", as Georgeos suggested, or "mountain metals", the more 'generic' meaning that I have suggested.