I'm a terrarian since around 2012, when Terraria was still in version 1.1.
I forged my Excalibur a long time ago from the good old cobalt, mythril and adamantite swords. Once Terraria 1.2 got introduced, I used that exact sword for the Terra Blade. And now in Terraria 1.4, I used that Terra Blade for my Zenith. So my Zenith technically contains cobalt, mythril and adamantite.