Vintage Diamond & Onyx Cocktail Ring in PlatinumVintage Diamond Onyx Cocktail Ring in Platinum. This antique Art Deco cocktail ring features 3. 37 carats of Old European cut diamonds set in platinum and surrounded by pieces of square cut onyx. The three diamonds sit north south along the finger in milgrain adorned bezel settings that appear to be floating inside their onyx frames. This ring is a great example of the fabulous angular style of the Art Deco era and is a perfect piece to accompany you