Sun Opal and silver necklace

Sparkling faceted sun opal (I think) and silver necklace. It's very shiny and hangs beautifully. Stamped as sterling, but it feels light to me, and I've priced it to reflect that. I bought this year's ago, and I've never worn it, but I believe the stones are sun opals. They're not moonstone, though they often get mislabeled as such.