Antique 20 Carat Amethyst Cocktail Ring in 18k Yellow Gold.  This beautiful Mid-Century cocktail ring features a spectacular 19.97 carat oval cut amethyst set in 18 karat yellow gold. The mounting is made of a wonderful lattice of gold wires overlapping and creating lovely open spaces. Held by four prongs, the focal point of this ring is obviously the amethyst and this vintage mounting does a perfect job of highlighting its natural beauty.