Logan Sapphire

The Logan Sapphire is a 422.98 carat blue sapphire from Sri Lanka, one of the largest faceted gem-quality blue sapphires in existence. The stone is a mixed cushion cut, blue with slight violet overtones, and measures 49.23 by 38.26 by 20.56 millimeters, roughly the size of a large chicken egg. It is mounted in a silver and gold brooch framed by 20 round brilliant cut diamonds totaling about 16 carats, making it the largest and heaviest mounted gem in the Smithsonian's National Gem Collection. A Gemological Institute of America report from June 1997 found the color natural, with no evidence of heat treatment.

The sapphire was owned by Victor Sassoon before M. Robert Guggenheim purchased it and gave it to his wife, Rebecca Pollard Guggenheim, in 1952. She deeded four-sevenths of the gem to the Smithsonian Institution in December 1960 and transferred the remainder in 1961. The stone takes its name from her later marriage to John A. Logan in 1962. It has been on display in the National Gem Collection at the National Museum of Natural History in Washington, D.C. since 1971, where it carries catalog number NMNH G3703.