This is a spectacular vintage Art Deco 14K gold pendant necklace made of reverse carved rock crystal layered over carnelian with a small diamond in the center. The setting is 14K white gold filigree. It is in the same style as the rock crystal and camphor glass pendants that were popular in this era, however I have never seen one made this way. It is unmarked, but the stones have been tested with a gemstone tester and the metal acid tests to at least 14K.
The chain measures 16 inches and the pendant itself measures 1 inch by 3/4 inch and the bail is an additional 1/2 inch. It is in excellent condition with no visible damage.