Do the fossils in the ground break? Oh, my gosh, and HOW! A lot of it depends on the conditions that they’re found in. You see, the thing that makes them fossils is that the organic parts of bone get replaced over time with whatever minerals are already in the ground. If there’s not a lot of mineral content, or not that much geological time has passed, they can end up sort of swiss-cheesed, with only the non-organic bits like hydroxyapatite and calcium carbonate present, but not a lot of the organic cells and collagen.
So, sometimes, they’re very stable and essentially rocks themselves (full replacement of organic with minerals), other times, they’re very brittle, or even chalky (little or no organic and incomplete replacement; sometimes de-calcified to boot). Great care must be taken to preserve fossils so that they don’t disintegrate upon handling or after they’re removed from the environment they’ve been in.