One of the rarest diamonds in the world is on display at a New York City museum.

The fancy, deep grayish blue Wittelsbach-Graff Diamond was discovered in Indian in the 17th century.

The gem is 31.06 carats. It originally weighed 35.56 carats before it was recut to enhance its clarity and color.

It will be on display at the Museum of Natural History from Thursday through Jan. 2, 2011.

It was purchased by London-based jeweler Laurence Graff in 2008 for $24.3 million. Christie’s says that’s a world record for any diamond and jewel sold at auction.

The world’s largest known deep blue diamond is the 45.52-carat Hope Diamond, discovered in the 1600s. It’s on permanent display at the Smithsonian’s Natural History Museum in Washington.