Vaseline Glass Ashtray

I have a vaseline glass ashtray. I have been told that it appears to be either slag glass, jadeite glass, and I have had one antique dealer tell me that it appears to be jadeite with a hint of old milk glass (she looked around the edge of the glass and said it had a "fire" that old milk glass had). I don't know anything about it and would like to learn more about it. Any information about it would be nice, including the price if possible. Thank you.