|Whitney Alexandrite||NMNH G10613||Brazil, Minas Gerais||17.08 ct|
One of the most prized and exotic gemstones is the variety of chrysoberyl known as alexandrite. It is renowned for its dramatic color change from purplish-red under incandescent light to bluish-green in daylight or fluorescent light. Impurities of chromium cause alexandrite to transmit red and green light equally well. It was named after Czar Alexander II, on whose birthday the gem allegedly was discovered in 1830 in the Ural Mountains of Russia.* The original locality for alexandrite is Russia, however, fine gems have also been found in Brazil, Sri Lanka, Tanzania, Madagascar, Zimbabwe, India, and Burma. Alexandrites over 2 carats are considered large, and when over 5 carats, they are extremely rare. The spectacular 17.08-carat Whitney Alexandrite appears a raspberry color under incandescent light and a teal (green-blue) color when illuminated by daylight. With its exceptional size, clarity, and amazing color change, this gem is one of the finest known alexandrites from the Hematita Mine in Minas Gerais, Brazil. The Whitney Alexandrite is a beautiful modified cushion cut gemstone. It was generously gifted in 2009 by Coralyn Wright Whitney and is on display at the National Museum of Natural History.
*Nils Gustaf Nordenskiöld (1792-1865), a renowned Finnish mineralogist, is credited with the discovery of alexandrite. His initial discovery occurred while examining a newly found mineral sample he had received from Count Lev Alekseevich Perovskii (1792-1856). Nordenskiöld first identified it as emerald. Confused by the high hardness, he decided to continue the examination. While looking at the specimen under candlelight, he was surprised to see that the color of the stone had changed to raspberry-red instead of green. He confirmed the discovery as a new variety of chrysoberyl, and suggested the name “diaphanite.” Perovskii, however, used the rare specimen to ingratiate himself with the Imperial family. He renamed it alexandrite and presented it to the future Tsar in honor of his coming of age on April 17, 1834. However, it wasn't until 1842 that the description of the color-changing chrysoberyl was published for the first time under the name alexandrite. (information provided by Gustaf Arrhenius,2010)