My question is, does the whole gravel pocket need to be within levels 20 and 50 for the fossil to spawn?
I've found one fossil so far (and it was pretty random) but now I'm branch mining for them. If the whole gravel pocket needs to be within both levels then it will change my search quite a bit because there will no longer be point in mining on level 20 due to the high chance of a single block in the pocket being in level 19..
So if anyone who knows the answer (hopefully a coder who implemented fossil spawn rules) I would love to hear it