The Wittelsbach-Graff Diamond at the AMNH

Known as the "storied sparkler," the 31.06-carat Wittelsbach-Graff diamond was discovered in India, then given to the Spanish Infanta Margarita Teresa in 1664 and eventually inherited, confiscated, and auctioned in 1931 --- at which point it disappeared. Decades later, the extremely rare, fancy deep blue gem was purchased (for 16.4 million pounds), cleaned, re-cut, and loaned to the American Museum of Natural History, where it will remain until January 2.