They say: "you can see the whole universe in black opals." Our Nebula ring captures the beauty of opals. With 10mm in diameter, the big round black opal shines in beautiful, vivid red, green and even blue, which change depending on the light and angle. Set in massive gold, the sleek yet robust design emphasizes the centerpiece and brings full attention to this mysterious gem. bling. gems stand for sustainability and are 100% conflict-free. Our revenue funds projects in Africa to support communities that have been hurt by the natural diamond industry. Click here for more information. bling. opal ~ 10mm diameter Sustainable lab-grown black opal, identical to its natural counterpart, galaxy fire Recycled yellow gold Solid 18k (750) Sustainably sourced, exquisitely crafted All bling. diamonds with sizes 0.5ct and above are certified by the world's largest third-party gemological institute.