This is a gorgeous sterling silver Genuine Rainbow Moonstone pendant.
It is rare to find a Moonstone pendant that is round like this and this big.
The stone measures 32 mm across the diameter.
The sterling silver filigree work on this is amazingly detailed! It's beautiful craftsmanship.
The total length across the diameter of the pendant is 2 1/8 inches.
The moonstone is bezel set and raised in the setting to make it very 3-dimensional.
This appears to have originally had a pinback that was removed, and it was converted into a pendant.
The pendant is stamped 925 on the back and "Plata De Jalisco, JFCM Guad Mex".
I have photographed this in the best light to show its rainbow flash. Depending on how the light catches it, the flash of colors will vary - which adds to the mystery of the rainbow moonstone.
It's an impressive piece of jewelry!