Hi there,
For the room w/ the blocked off crystal, there's two paths to that room. If you're in the central chamber and head left, you'll be in a room with a small body of water, and three exits. One to the right, which takes you back to the central chamber, one to the left, which takes you to the room w/ the blocked off crystal, and one to the bottom, which is the path that loops back around to that blocked off crystal. :)
Thank you for the post! I've been concerned about the caves, so things like this help guide me in what to change in the future.