Allnatt Diamond

The Allnatt Diamond is a diamond measuring 101.29 carats (20.258 g) with a cushion cut, rated in color as Fancy Vivid Yellow by the Gemological Institute of America. This diamond was named after one of its holders, Major Alfred Ernest Allnatt, a soldier, sportsman, art patron and benefactor.

The Allnatt's origins are unknown prior to Major Allnatt's purchasing of the diamond in the early 1950s. After purchasing the diamond, he commissioned Cartier to make a setting for it. The final setting was a platinum flower with five petals, a stem and two leaves, all set with diamonds. The Allnatt was resold at auction in May 1996 by Christie's in Geneva for $3,043,496 US. At the time of its sale the Allnatt was 102.07 carat. and was graded Fancy Intense Yellow. After being sold to the SIBA Corporation, the diamond was re-cut to its current weight and the intensity was upgraded as a result.

The Allnatt was displayed as part of the Smithsonian's "The Splendor of Diamonds" exhibit, alongside The De Beers Millennium Star and The Heart of Eternity.