Overview This stunning boat-shaped sapphire and diamond cluster ring features a central oval brilliant-cut blue sapphire that is not only a huge 4.60 carats but also exhibits the much coveted and rare 'Royal Blue' colour, the most prized blue of all blue sapphires. With excellent saturation of colour it is exceptionally pleasing to the eye. Surrounded by bright and lively round brilliant-cut diamonds in a classic border cluster style. French assay marks to the shank. This ring is fantastic value.