As stated above it is indeed an insulator.
Some of the prcelains are worth a a bit, but it is hard to tell what you have here from the view. Can you describe it a bit better? It looks like is call a multipart...which means it has more than one part cemented together.
More than likely it is a very common piece, and worth little to nothing considering the shape its in, but you never can tell until we see the whole thing. If you can get a better pic and take notes of any markings on it I can give you a value.