The colossal gem, which Christie's said was the finest and largest perfect Golconda diamond ever to appear at auction, is perfect in color and internally flawless.
The legendary Golconda mines in India produced some of the world's most famous diamonds, including the Dresden green, the blue Hope, and the Koh-i-Noor (in the Royal Collection at the Tower of London), Rahul Kadakia, head of jewelry for Christie's Americas and Switzerland, told Reuters.
The diamond, named the Archduke Joseph Diamond for one of its former owners, is the highlight of Christie's sale of precious gems in Geneva in November, the auction house said in a statement.
A Christie's spokeswoman said the owner of the diamond wanted to remain anonymous. Prices for rare, top quality diamonds have soared in recent years, although the expected price would not make the record books. Higher prices attained in recent years include the Wittelsbach Diamond - a 17th century cushion-shaped deep grayish-blue diamond, which sold for $24.3 million in 2008 at Christie's in London.
Two years ago a 25-carat pink diamond soared to more than $46 million at Sotheby's in Geneva, while last December Hollywood star Elizabeth Taylor's 33-carat diamond ring, given to her by husband Richard Burton, fetched $8.8 million, briefly setting a new per carat record for a colorless diamond of $240,000 that has already been eclipsed.
The Archduke Joseph Diamond created a sensation when Christie's Geneva offered it for sale the first time in November 1993, where it realized 9.7 million Swiss francs ($6.5 million) - the equivalent of $10.5 million today, noted Franois Curiel, international head of Christie's jewelry department.
Given its history, Curiel said the diamond could easily top $15 million in the upcoming auction.
The gem is named for one-time owner Archduke Joseph August Viktor Klemens Maria, son of Archduke Joseph Carl of Austria and Princess Clothilde of Saxe-Coburg and Gotha, Christie's said.
Born in 1872, he was the great-grandson of Emperor Leopold II through his father, and the great-grandson of King Louis Philippe of France through his mother.
South central India 's Golconda diamond fields trace their roots to 400 B.C, and along with a mine in Borneo were the sole source of diamonds up until about 1725, when diamonds were discovered in Brazil.
The diamond will be auctioned in Geneva on Nov. 13, following an exhibition tour in New York, Hong Kong and Geneva.