Vintage best Arts & Crafts Boulder Opal silver hand crafted pendant necklace

One-of-a-kind handmade polished boulder opal pendant set in silver alloy. I'm not sure of the metal content. The leaves are highlighted with green and blue enamel. There is a 24" braided black string necklace on it at the moment which can easily be replaced or wear as is. From what I can gather I believe this is an Australian boulder opal? Has good weight best to it and a good setting, nice and tight. Most likely from the 1970's to 1980's? It's very hard to tell and I don't see a signature anywhere.