(IDEX Online) - The most expensive piece of jewelry in the history of Tiffany & Co, a diamond necklace valued at up to $30m, made its debut appearance when Beyonce wore it for an Oscars after-party.It's a a modern take on the jeweler's iconic 1939 World's Fair Necklace, and it features a total of 578 diamonds, with a total weight of 180 carats set in platinum.At is center is an 80-carat oval shape, D-color, IF-clarity gem called The Empire Diamond, which can readily be removed and mounted on a ring.Beyonce became the first person to wear the necklace at a party she hosted, together with husband Jay-Z at the Chateau Marmont hotel in Los Angeles last week.The original necklace, an American Art Deco highlight of the 1939 World's Fair in New York, was set with an aquamarine stone weighing over 200 carats and 429 diamonds. It was priced at $28,000 (or about $557,000 by today's value).