This huge emerald is set in an art deco diamond and platinum pendant designed by Cartier. In 1931, Clarence Mackay gave the necklace as a wedding gift to his wife, Anna Case– a prima donna at the New York Metropolitan Opera from 1909 to 1920. The Mackay emerald, with a weight of 167.97 carats, was mined in Muzo, Columbia, and is the National Gem Collection's largest cut emerald. The emerald is set in a pendant-style platinum necklace, accented by an additional 35 emeralds and 2,191 diamonds. Mrs. Anna Case Mackay donated the necklace to the Smithsonian Institution National Museum of Natural History in 1984.