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January-February 2016

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The Royal-Blue Logan Sapphire at the Smithsonian Institution

Although the Hope Diamond is the most famous blue gemstone at the Smithsonian Institution, it's not the only one!

AT 422.98 CARATS, the Logan Sapphire is the largest mounted gemstone in the Smithsonian Institution's National Gem Collection. The sapphire, which was found in Sri Lanka, is faceted as a mixed cushion cut and is blue in color with very slight violet overtones. Under longwave ultraviolet radiation the stone fluoresces a moderate reddish-orange. A Gemological Institute of America report dated June 1997 states that the Logan Sapphire's color is natural with no evidence of heat treatment detected. The sapphire is mounted in a silver and gold brooch setting and is surrounded by twenty round brilliant-cut diamonds, totaling approximately 16 carats.       

Russell C. Feather II is the collection manager of the National Gem Collection in the Department of Mineral Sciences at the National Museum of Natural History (Smithsonian Institution).       

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