Amethyst geodes generate so frequently that they can generate inside of each other. Geodes being able to do this is not mentioned in any sort of changelog.

How to reproduce:

1. Generate a world with the seed 736346737306014324
2. Go to the coordinates -2594 42 1043
3. Change your gamemode to spectator and look down
4. You can see two geodes that generated inside of one another.