18-karat yellow gold Faceted and cabochon oval, round and pear-shaped bezel-set and prong-set London blue topaz, green gold citrine over pyrite doublet, peridot and green amethyst gemstones = 37.00 ct. tw. Shepherd's hook backs It is customary to treat most gemstones to achieve enhanced color and durability. Some of these treatments may not be permanent, and may require special care.