Is it even a fossil?

[HeatherMF]

[ynot]

It could be a fossil, but it is also an extant species of sea snail, so hard to be sure.

[HeatherMF]

I was debating the same question. My main thought was that I don't recall seeing a shell so thick before. 

[caldigger]

Heather, is this from a specific deposit or found loose on the beach?  I have some seashells that are from a Pliocene deposit near me that is from a site some 8- 10 feet above sea level. If you know where these are coming from, it might help to aid in identification.

[izak_]

Without further information, I doubt it is fossil. The non-uniform colours are a tell-tale sign. The best way to tell is putting it in vinegar for a couple of minutes, then show us the result. That will get rid of the white layer on the shell's surface. 

[HeatherMF]

I'll try that, but after my visit today, I don't think it's a fossil either,  since I saw some similar ones crawling around with little crabs in them. Quite cute little blueish crabs.