Platinum Natural Black Opal and Diamond Ring. The ring is set with an oval cabochon black opal measuring 20.12 x 16.70 x 8.83mm., weighing apprx. 17.00cts. with AGL #1087659, natural with no treatment, further set with two half moon diamonds, apprx. .45cttw., and 12 full cut diamonds, apprx. .30cttw., G/VS, size 8.