Moonstone Ring Rhode Island What Is The Difference Between A Moonstone And An Opal?

What is the difference between a moonstone and an opal? - moonstone ring rhode island

I have this ring very comfortable in my mother's house, but the seller was not really sure, was what kind of stone ring. She said it was either a moonstone or opal, but since the ring is quite old, it's hard to say. Thank you.