Damascus steel
Damascus steel - “It is said that when Damascus made swords were first encountered by Europeans during the Crusades it garnered an almost mythical reputation — a Damascus steel blade was said to be able to cut a piece of silk in half as it fell to the ground, as well as being able to chop through normal blades, or even rock, without losing its sharp edge. Recent metallurgical experiments, based on microscopic studies of preserved Damascus-steel blades, have claimed to reproduce a very similar steel via possible reconstructions of the historical process.”
I don’t know about cutting through rock, but it is interesting how the process of fabrication of this alloy was lost and found throughout time.