This item is a black faceted beaded necklace that exhibits an iridescent sheen, likely an Aurora Borealis (AB) finish, which gives the beads a colorful blue and purple flash when they catch the light. These types of necklaces are often made with glass or crystal beads and are a popular style in vintage costume jewelry. The necklace is a long, loopable or double-strand design, allowing it to be worn in different lengths. The beads are faceted, which enhances their sparkle. They are likely glass or crystal, possibly with an Aurora Borealis (AB) coating that creates the iridescent effect. The base color is black, but the finish gives it an oil slick or rainbow-like flash, most notably blue.