September 10th, 2026
Imagine a sapphire the size of a large chicken egg, weighing nearly 423 carats and glowing with a rich blue hue touched by the faintest whisper of violet. That is the Logan Sapphire, one of the world’s most spectacular faceted blue sapphires and a dazzling centerpiece of the Smithsonian National Gem Collection. It's also an amazing example of September's birthstone.
Weighing 422.98 carats, the cushion-cut Logan Sapphire is believed to be the third-largest faceted blue sapphire in the world. The only ones larger are the 486.52-carat Blue Giant of the Orient and the 478.68-carat Queen Marie of Romania Sapphire.
The Logan Sapphire’s impressive size is only part of its appeal. The mixed cushion-cut gem is blue with very slight violet overtones and measures roughly 49 by 38 by 21 millimeters. It is mounted in a silver-and-gold brooch surrounded by 20 round brilliant-cut diamonds totaling approximately 16 carats. The piece holds the distinction of being the heaviest mounted gem in the Smithsonian’s National Gem Collection.
The sapphire was cut from a crystal mined in Sri Lanka, historically one of the world’s great sources of fine sapphire. Before reaching America, the gem was owned by Sir Ellice Victor Sassoon, third Baronet of Bombay. The Sassoon family reportedly acquired it from an Indian maharajah, after which Col. M. Robert Guggenheim purchased it.
In late 1952 or early 1953, Guggenheim presented the spectacular brooch to his wife, Rebecca Pollard “Polly” Guggenheim, as a Christmas/anniversary gift. The enormous sapphire might seem like a challenging piece of jewelry to wear, but Polly apparently embraced its grand scale. When asked whether her 422.98-carat sapphire brooch was perhaps too large to wear, she reportedly replied, “I thought so too until I owned it.”
Polly donated the sapphire to the Smithsonian in December 1960, although she retained possession of it for another decade. In April 1971, she sent the brooch to Washington, DC, and formally presented it to Smithsonian curator Paul Desautels for public exhibition on June 22. By then, Polly had married John A. Logan, providing the name by which the famous gemstone is known today.
A 1997 Gemological Institute of America report determined that its color is natural and found no evidence of heat treatment. Under longwave ultraviolet light, the sapphire exhibits moderate reddish-orange fluorescence.
Like all sapphires, the Logan is a variety of corundum. Trace elements introduced naturally into the crystal structure give the gemstone its color, with iron and titanium contributing to the blue hues. Its Sri Lankan origin places it among the celebrated “Ceylon” sapphires prized by collectors.
Sapphires are seen in many colors, including pink, purple, green, orange and yellow. Ruby is the red variety of corundum.
Credit: Photo by Chip Clark/Smithsonian, and digitally enhanced by SquareMoose.
Weighing 422.98 carats, the cushion-cut Logan Sapphire is believed to be the third-largest faceted blue sapphire in the world. The only ones larger are the 486.52-carat Blue Giant of the Orient and the 478.68-carat Queen Marie of Romania Sapphire.
The Logan Sapphire’s impressive size is only part of its appeal. The mixed cushion-cut gem is blue with very slight violet overtones and measures roughly 49 by 38 by 21 millimeters. It is mounted in a silver-and-gold brooch surrounded by 20 round brilliant-cut diamonds totaling approximately 16 carats. The piece holds the distinction of being the heaviest mounted gem in the Smithsonian’s National Gem Collection.
The sapphire was cut from a crystal mined in Sri Lanka, historically one of the world’s great sources of fine sapphire. Before reaching America, the gem was owned by Sir Ellice Victor Sassoon, third Baronet of Bombay. The Sassoon family reportedly acquired it from an Indian maharajah, after which Col. M. Robert Guggenheim purchased it.
In late 1952 or early 1953, Guggenheim presented the spectacular brooch to his wife, Rebecca Pollard “Polly” Guggenheim, as a Christmas/anniversary gift. The enormous sapphire might seem like a challenging piece of jewelry to wear, but Polly apparently embraced its grand scale. When asked whether her 422.98-carat sapphire brooch was perhaps too large to wear, she reportedly replied, “I thought so too until I owned it.”
Polly donated the sapphire to the Smithsonian in December 1960, although she retained possession of it for another decade. In April 1971, she sent the brooch to Washington, DC, and formally presented it to Smithsonian curator Paul Desautels for public exhibition on June 22. By then, Polly had married John A. Logan, providing the name by which the famous gemstone is known today.
A 1997 Gemological Institute of America report determined that its color is natural and found no evidence of heat treatment. Under longwave ultraviolet light, the sapphire exhibits moderate reddish-orange fluorescence.
Like all sapphires, the Logan is a variety of corundum. Trace elements introduced naturally into the crystal structure give the gemstone its color, with iron and titanium contributing to the blue hues. Its Sri Lankan origin places it among the celebrated “Ceylon” sapphires prized by collectors.
Sapphires are seen in many colors, including pink, purple, green, orange and yellow. Ruby is the red variety of corundum.
Credit: Photo by Chip Clark/Smithsonian, and digitally enhanced by SquareMoose.
