925 Sterling Silver Single Opal Earring By EFFY (?)

Classic stud earring with a shimmering fire opal centerpiece. Single earring, suitable for a third hole, or an asymmetric look. The back is stamped 925 EFFY. The earring post is not stamped. Don't know what the metal is. Could be 925 sterling silver, or white gold / gold plated, or platinum / rhodium plated. The opal stone is natural and has good fire, as shown in the video. It has a tiny surface hairline,c which I can't capture on camera, and also one small imperfection on the edge (last picture, bottom right).