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Logan Sapphire [G3703]
CorundumRubies and sapphires are varieties the same mineral: corundum. Pure corundum, composed of aluminum and oxygen atoms, is colorless. Color variations come from light interacting with impurities that replaced atoms of aluminum in the growing crystals.
Hover over color tiles above to learn what this object tells us about the history of the Earth
About this object
The magnificent 423-carat Logan Sapphire was cut from a crystal mined in Sri Lanka and is one of the world’s largest faceted blue sapphires (it is about the size of an egg). It is the heaviest mounted gem in the National Gem Collection, and in its silver and gold brooch setting is framed by twenty round brilliant-cut diamonds, totaling approximately 16 carats. Historically the finest sapphire gems came from Sri Lanka, Burma, and the Kashmir region of India. Sri Lanka, nicknamed the “Gem Island,” has been an important source of sapphires, rubies, and other gems for more than 2,000 years. Sapphires from Sri Lanka are typically light to medium blue in color and are commonly referred to as “Ceylon Sapphires.” As seen here, the Logan Sapphire has a beautiful medium soft violetish blue color and exceptional clarity, especially for a stone of its size. It was examined by the Gemological Institute of America in 1997 and found to be a natural sapphire of natural color with no evidence of heat treatment. The Logan Sapphire was donated to the Smithsonian in 1960 by Mrs. John A. (Polly) Logan, a Washington socialite, and is on display in the Gem Gallery at the National Museum of Natural History.
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