While in true mythology silver has many powers nothing is ever said of it in greek mythology.

In greek mythology it is true that people defeat monsters with common weapons however majority of common weapons were forged from bronze and copper which if mined from mount Olympus wound make them celestial bronze weapons. Hercules was able to kill beast with his bare hands because he was immortal having drunk the breast milk of Hera.

When civilization moved on the sacred metals were left behind but in the times greece they would have been considered common and it would have been unnessesary to mention what the weapon was made with.