Couldn't find much about korund on the forum, but just to clarify - is it really this difficult to acquire?
With a 350 pickaxe and close to 800 strength, I "can't even mange to scratch that (what looks like korund) rock."
Just trying to drop the next level minehole. The korund is all I lack (except the pink brick, but I'm working on potter now)
I certainly don't expect to find any stones laying around this late in the game