Rings › 18ct Yellow Gold Opal & Diamond Cocktail Ring Image 1 of 1 18ct Yellow Gold Opal & Diamond Cocktail Ring £3,950.00 Vintage 18ct Yellow Gold Opal & Diamond Cocktail Ring. Size S, however, this ring can be resized in our workshop if needed. Quantity: Add To Cart Added! Vintage 18ct Yellow Gold Opal & Diamond Cocktail Ring. Size S, however, this ring can be resized in our workshop if needed.