Blue diamond to sell for $19 million

The world's largest round blue diamond is expected to make quite a splash at an auction in Hong Kong. Named "The Premier Blue," the stone was graded by the Gemological Institute of America and is expected to sell for about $19 million, according to Bloomberg. It was so named because it comes from Pretoria, South Africa's Premier mine, which acts as the main source for blue diamonds in the world. Jewelry experts believe that the round diamond cut adds to this stone's desirability.

"The market for colored stones is strong because of their rarity," Guy Burton, director at London's Hancocks, explained in an interview. "People buy them for investment purposes and they can be seen as a hedge against what happens in other markets."

Blue diamonds are considered to be one of the most precious because they account for less than 1 percent of all the diamonds that are mined. According to LiveScience, the intense blue color comes from the mixture of carbon and boron atoms that constitute the diamond's make up. The more boron that is present, the deeper the blue.

The Premier Blue weighs 7.59 carats and will be auctioned off on Oct. 7 as part of Sotheby's 40th anniversary celebration.