.99 Mid-Century Marquise Diamond Ring in 18k Yellow Gold and Platinum.  This fabulous Mid-Century ring features a .99 carat marquise cut diamond set in 18 karat yellow gold and platinum. The chunky marquise is wrapped in a halo of channel set emeralds, and also a halo of round diamonds. The emerald accents are set in a channel of milgrained yellow gold with a slight gap of open space separating it from the center stone. The shank of this ring is made of 18 karat yellow gold which contrasts nicely with the platinum securing each of the diamonds. A bold and colorful vintage ring with a wide marquise diamond that is truly stunning.