The Cullinan Blue Diamond Necklace is a historic piece of jewelry that was presented by Thomas Cullinan, then-chairman of the Premier Mine in South Africa, to his wife Annie, around 1910. The gift was to commemorate the largest rough diamond ever mined -- the 3,106-carat Cullinan diamond, discovered in 1905. Cullinan did not keep this gem for himself. Instead it was presented to King Edward VII of England by the Transvaal government, and Cullinan was subsequently given knighthood. Nine major pieces were cut from the original Cullinan rough; the two largest stones are in the British Crown Jewels, and the other seven stones are in the private collection of Queen Elizabeth II. The necklace was temporarily exhibited at the Smithsonian in 1994 and was formally donated by Mr. Stephen Silver, a jeweler from California, to the National Gem Collection in 2010.

Hall Sapphire Necklace, posted earlier: