An Art Deco single stone black opal ring, An Art Deco single stone black opal ring, with diamond set shoulders. A circular tallow cabochon cut black opal, milligrain set to each shoulder, to a ridged shank. Tested and valued as platinum. Head 27.50mm x 14.80mm, 3.87g. Ring case by B J Tully, 10A New Bond Street, W1 Finger size K/L Buying this gemstone ring at auction could save up to 0.42 tonnes of CO2e compared to buying new. Condition Report: 1x circular cabochon black opal. Very shallow crown, cabochon back. Navy blue body colour to the underside, possibly N4/N3. Mixed colours to the crown, red, orange, electric blue, green, mauve, yellow. Rolling flash. Possibly floral or floral harlequin. 13.90 x 12.98 x 5.00mm NB - the milligrain setting edge conceals any possible join to determine if this is a doublet, however the body colour suggests probably natural.