 | The Kazanjian Red Diamond is an extraordinary 5.05-carat red gem that was on temporary display in the Museum's Morgan Memorial Hall of Gems. Red diamonds are the rarest among colored diamonds. Only three 5-carat red diamonds are known to exist: the Kazanjian Red diamond, the trilliant-cut 5.11-carat Moussaieff Red, and the 5.03-carat De Young Red. The original 35-carat piece of rough was discovered in Lichtenburg, South Africa |  |
 | At 563 carats, the Star of India is the world's largest gem-quality blue star sapphire. Rutile, a mineral in the Star of India, gives the gem its milky quality and star effect. Tiny fibers of rutile in a three-fold pattern reflect incoming light in the star pattern. This effect is called asterism. |  |
 | The Patricia Emerald is a large and superbly colored specimen. At 632 carats, the dihexagonal, or twelve-sided, crystal is considered one of the great emeralds in the world. Found in Colombia in 1920, it was named after the mine owner's daughter. The flaws in this emerald are normal but compromise the hard gem's durability. This specimen is one of the very few large emeralds that have been preserved uncut. |  |
 | The Kimberley Diamond was originally discovered as a 490 carat crystal. The Kimberley diamond was cut into a 70 carat gem in 1921. According to the museum, the stone was given its present emerald cut in 1958 to improve its brilliancy. |  |
http://www.amnh.org/exhibitions/permanent-exhibitions/earth-and-planetary-sciences-halls/morgan-memorial-hall-of-gems
