Vintage 1930s Art Deco, estate purple amethyst oval, framed with marcasite stones, sterling silver pendant, on a 16" white gold filled chain.  Bail is stamped STERLING.  Pendant measures 1"L x 3/4"W, and weighs 5.7 grams.  Chain necklace spring ring clasp is stamped 1/20 12 Kt G F, the fastener ring is stamped NS in a diamond shape hallmark, and it weighs 2 grams.  Pre-owned. Missing one marcasite stone, on the left side.  The necklace may not be original to the pendant.  Thank you for looking.