Large opal and diamond cluster ring

This unusual ring features a large oval cabochon cut opal set within multi-claw 18ct yellow gold mount, surrounded with a row of round eight-cut diamonds. The diamonds are set within 18ct white gold with an 18ct white gold under-bezel. Chénier shoulders and tapered shank of 18ct yellow gold. 
The opal measures 19mm x 13mm. 
The cluster measures 25mm x 20mm.