There is a bug with the legendary pickaxe and vampirism. If you kill an enemy with the vampirism tick of your pickaxe attack, the pickaxe actually gives you the gem twice. Pretty fun bug. Encountered it a couple times on a pickaxe run where I had two vampirism stones. The amount of times enemies dies to the final 2 vamp damage and I got to pick gems twice was noticeable. Encountered it a couple days ago so not sure if fixed, but haven't seen anyone else mention it when scrolling the comments.