The Logan sapphire is named after Mrs. John Logan who donated the gemstone to the Smithsonian Institute in 1960. The Logan sapphire is a flawless specimen, possesses a rich blue color and is the second largest (blue) sapphire known, weighing 423 carats. The Smithsonian castle, as seen through the garden gate. ... Jump to: navigation, search 1960 was a leap year starting on Friday (link will take you to calendar). ... Jump to: navigation, search Sapphire is the single-crystal form of aluminium oxide (Al2O3), a mineral known as corundum. ... Meanings of Carat or Karat: Carat is a unit of mass for gems. ...

The cushion-cut stone is one of the world's most famous sapphires and is set in a brooch surrounded by 20 round brilliant cut diamonds weighing in total 16 carats. Jump to: navigation, search Sapphire is the single-crystal form of aluminium oxide (Al2O3), a mineral known as corundum. ...

The Logan sapphire originates from Sri Lanka a famous location for sapphires. Jump to: navigation, search Sapphire is the single-crystal form of aluminium oxide (Al2O3), a mineral known as corundum. ...