54.3 71.0 on lost island look to find a massive cave with little entrance go past boat.

If you play on extinction break the trees with white leaves, they give blue crystilized sap which works like this. Becareful because corrupted creatures hurt. Would recommend going near the desert some because worst thing is corrupted rex

Tip for first time getting these things:

There’s a little “staircase” down to the bioluminescent on abberation (it’s the only land entrance that doesn’t require a jump, iirc) which is a transition zone. There’s a fair amount of blue gems for the taking. Be prepared to fight off various creatures on the way and while there (rock drakes, too).

Roll rats sometimes drop blue gems as well if you are on abberation. Only works if they are wild though.

Don't know where to find on fjordur, I assume in the aberration caves

Can you find them on the island