The Logan Sapphire Brooch, National Museum of Natural History, Washington DC
The Logan Sapphire is a flawless specimen from Sri Lanka, a cushion-cut stone which possesses a rich deep blue color and is the second largest (blue) sapphire known, weighing 422.99 carats (84.6 g).
The cushion-cut stone is one of the world's largest and most famous sapphires. The gemstone is one of the world’s largest sapphires (its size about that of an egg) that was cut from a crystal mined in Sri Lanka. The Logan Sapphire is named after Mrs. John Logan, who donated the gemstone to the Smithsonian Institution in 1960.