What gemstone would make the strongest sword?

I have been wondering... For a while I had been thinking that the most epic sword would be a "Diamond Sword". However I recently found out it would be a poor material to put in a blade. So I have not given up hope that you could make a awesome sword out of some precious material. (Not metals that are usually used in swords, such as Steel, and Iron. Of course Or even Gold, or Platinum.) I mean such as Jade, or Sapphire, or Ruby. Something of the sort of a gemstone. I have just been wondering haha! A interesting thought huh?