have you looked inside the band to see if it has any hallmarks? Precious metals are usually hallmarked, but not always, say, if it what made by a studio jeweler, then it might not be marked. The stone is beautiful - whatever it is!
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Grandma's ring by: Marga
Hallo, very nice ring. It could also be a fine ring but you need to know the material. Are there any hallmarks (use a loupe please to see better)? And if so please what do you see? If it's a gold ring there could also be some diamonds. Have they an open setting under the stone? Make, if possible a photo of the mark (also taken through a loupe) so we can see what there is. Awaiting to see you anwers and photos, succes!