Antique Swedish Import Sterling Silver Green Onyx Clip On Earrings

These are beautiful. I'm not entirely sure what the stone is. I saw another similar listing that called them green onyx. They might be glass or some other type of stone. The stone is a very unique piece that transforms with shades of green. The earrings are marked on the side with 3 crowns in an oval and the letter s in an octagon. The crowns is a mark for Swedish imports and the S signifies sterling silver. they measure approx. 7/8" x 1/2".