A boulder opal dress ring, claw-set with a triangular polished boulder opal, displaying vibrant play-of-colour mainly ranging from green to purple, on a dark ground and ironstone matrix to the base, 13.6 x 9.5 x 3.1 mm, adorned with a diamond accent, between crossover shoulders to flat shank, yellow metal marked '18ct', size O, 3.5 grams.