This is a beautiful vintage Art Deco filigree pendant necklace with a rhodium finish. The rectangular filigree pendant is set with a small blue glass stone in the center and it has gold colored highlights (most likely gold plating but it isn't possible to test this). It is suspended from a filigree station and it is attached to a fancy chain. It fastens with a slide catch which is marked Sterling. It also has a maker's mark which I can't identify. The rhodium finish is not on the chain, just the pendant.
The chain measures about 17 inches and the pendant is about 1 1/4 inches by 3/4 inch. It is in very nice condition.