Today I went driftwood hunting and found a ton at the local beach. However, I have no clue what's safe to be use and what isn't. How do I tell? And is it all safe to use if I boil it to death? I also noticed some of the pieces I got are a bit crumbly (e.g. flecks of wood come off into the water). As long as I soak it to the point that this doesn't happen anymore, is it still good to use?