Vintage Onyx Diamond Cocktail Ring 18k Yellow Gold. This breathtaking Mid-Century ring features .54 carats of diamonds and black onyx finished in polished 14 karat yellow gold. The deep black center onyx is cabochon cut and set in four prongs. Eighteen (18) single cut diamonds are pave set in stylish cuffs on the shoulders of the band. A bubbly, rounded vintage mounting in 14k yellow gold gives this ring a unique and beautiful character!