amethyst geode generating fully uncovered

What I expected to happen was...:

I expected the geode to be covered in stone, but it was totally uncovered

What actually happened was...:
Geode fully discovered in cave

Steps to Reproduce:
1. Enter in an map in this pre release
2. find an cave, then find an amethyst geode
3. Probably the geode will be discovered

World creation:

World type: Default

Generate structures: On

Bonus Chest: Off

Seed: in an print

Coordinates: In an print