Hi Stephany,
it is a pendant made of two shells of chitons, which are polyplacophoran mollusks having a shell formed by eight plates. I bought one identical in Dominican Republic one dozen years ago.
Giorgio
I thought they might be plastic, but they're too beautiful...
So glad you posted these, Stephany, and thank you, Giorgio!
I would run down the my studio to get a photo, but that will have to wait a few more weeks. Somebody bug me in a month!