12x10mm opal triplet set in sterling silver with an 18" sterling silver chain. Dimensions: .66 by .4 inches. This is a genuine opal from Australia. It has good play of color in green, red, blue and orange. Opal triplets are thin opals that have been backed for strength and then a clear crystal placed over the front for protection. When done, they are stronger than a full opal because they are totally protected.