Opals & Gems of Australia natural Opal Doublet (2.37cts) pendant set in 925 Sterling Silver (0.90gms) and plated in Rhodium to prevent tarnishing.. Size of pendant is 16x21mm, irregular gemstoneshape. Opal gemstone measures 10x13mm. Bail fits up to 2mm. Opal gemstone has beautiful midnight blue and neon green coloring. This pendant will showcase its beautiful coloring in natural sunlight. Opal, a precious gemstone, was called the Queen of Gems by the ancient Romans because it included the colors of all other gems. Opal is prized for its unique play of color, the ability to diffract light into flashes of rainbow color. Opal is the October birthstone.