Sterling Silver and Black Onyx Necklace with Round Pendant/Enhancer

Wear it with a pendant or without. Sterling silver and black onyx necklace with round pendant/enhancer holder. Faceted black onyx 6mm beads with sterling silver decorative front with circle pendant/enhancer holder with security clasp as seen in image 6. Necklace measures 18.5 inches long plus a 2 inch extender, marked BC and 925.