Looks like it was once mud on the sea floor. Interesting. A friend of mine once found a a giant fossilized shark tooth on the coast of SC after Hurricane Hugo. That thing was about 6" wide at the base. We had never seen anything like it. Years later, we find out from watching TV it was from an extinct species, Mega-something, anyway, a giant shark. The storm surge had apparently uncovered it, or washed it ashore.