This is a deeply saturated Opal stone which is predominately blue. It is @9 mm by 10 MM measured in the setting so @2.5 CT. The ring is size 6.5 and weighs 6.5 grams. It has interesting detail and the @0.25 CT Brilliant cut Diamond helps draw the eye.
It is in excellent estate condition with richly hued gold setting and is a unique style in Opal. Gorgeous.