O&G Australia genuine opal doublet stud earrings set in 925 Sterling Silver and plated with Rhodium to prevent tarnishing. Stud earrings measure 4x6mm. Earrings have 1 CZ round stud. Earrings have midnight blue and flashes of neon green coloring. 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.