Hand hammered Vintage Brooch

This is such an unusual brooch and one that I first thought as being enamelled but research has brought up a gemstone called Ruby Zoisite which does look identical. The piece has been set in a hammered metal frame with overall dimension 5cms across. There is a firm roll over safety clasp to the back. No provenance, so not sure of the age but certainly a little different and the purple and green surface is beautiful. The catch would suggest not a lot of age to the piece.  In excellent condition, gift boxed by Vintageonline.