These necklaces are unique and make quite a statement! Made using sterling silver and antique uranium glass, each is one of a kind. Set on either sterling silver or black enamel/gold chain - you choose! The Ourobouros piece is the only piece cast in bronze Uranium glass was popular in the late 1800s and early 1900s when a small amount of uranium was added to glass to strengthen it. Safe to humans and black light reactive, it went out of favor in the 1930s, but pieces can still be found today! Al