Well, well... I learn something new every time you post. I did not know the turtle shell was considered a bone. Also, as evidence by the inside of the shell you were enhancing, it incorporates the turtle's spine. I wonder how the alcohol inks would work on horseshoe crab shells. They are not bone but are a cellulose-like material called chitin (not to be confused with the world-famous blues singer Blind Melon Chitlin) Anyhow, if you want to experiment with them, I can gather a few hundred off the beach tomorrow and ship 'em up to ya. Cheers.