In addition to the Tiffany Diamond, the necklace also features 16 cushion-cut diamonds and 46 round brilliant diamonds. But it’s not just the size and provenance of the stone that makes Lady Gaga’s accessory so special. The last time this piece of jewelry left the Tiffany vaults was for a promotional shoot Breakfast at Tiffany’s—which makes Audrey Hepburn the last person to wear it publicly.

At 128.54 carats, the Tiffany Yellow Diamond is the world’s second-largest Canary Yellow diamond.

The Tiffany Yellow Diamond is the second-largest Canary Yellow diamond in the world and has been owned by Tiffany & Co since 1878.

The cushion-cut diamond measures 28.25 X 27 X 22.2 millimeters and features an unusual number of facets: 48 on the pavilion and 40 on the three-stepped crown, as well as table facets and an arrangement of facets that radiate out from the diamond’s culet in a star shape.

The stone has been owned by Tiffany & Co since 1878. There are no confirmed records of its origin, but it is believed to have been discovered in 1877 or 1878 at one of the Kimberley mines in South Africa belonging to the French mining firm Compagnie Francais de Diamant du Cap. The company sent it to Paris, where a Tiffany agent paid $18,000 for the 297.42-carat rough stone.

Once Tiffany & Co procured the yellow diamond, the firm’s gemologist, Dr. George Frederick Kunz, was charged with finding the optimal cut. It took nearly a year to cut the diamond into its current form. Some believe that the number of facets were de

signed to reduce the diamond’s brilliance, giving it a “smoky” rather than a “fiery” appearance. The unusually high crown and deep pavilion seem to indicate that it was cut to minimize weight loss.

The Tiffany Yellow has been on display in the diamond company’s flagship New York store for over 70 years. It was mounted in its current “bird on a rock” setting in 1995.

Over the years, the diamond has been offered for sale only a few times. In 1951, a price of $500,000 was negotiated but the deal fell through. In 1972 a notice in the New York Times informed the public that Tiffany & Co was selling the diamond for $5 million, and the last time the Tiffany Yellow was put up for sale – 1983 – it was valued at $12 million.