I recently took a trip to Sanibel island, and Key Marco. I brought back some lightning whelk shells. My first tool project was to make a shell hammer. Based on the blade, I call it an ax. I am still learning about these shell tools, so calling it a hammer seems kind of goofy for what it really seems to do.
Shell: Busycon perversum
Handle: Osage orange
Wrap: rawhide
Once it is good and dry I will find a tree to chop and see how it does.