Black Opal Diamond Necklace in Yellow Gold.  This modern opal and diamond necklace features an amazing black opal and a bright pear shaped diamond in a simple yellow gold design. The 2.13 carat black opal contains a spectacular red flash with green and blue coming through and creating a terrific color pallet. Above the opal sits a .57 carat pear shaped diamond that is bezel set with subtle milgrain edge detail.