Blue diamonds aren’t the rarest of the colored diamonds but they tend to do well at auction, larger stones often command top prices (a 7.03 carat stone sold for $9.49 million last year). Sotheby’s Hong Kong is hoping to get a big result for a 5.16 carat blue dimaond being auctioned off at the Hong Kong Magnificent Jewels and Jadeite Spring Sale on April 7. The pear-shaped fancy vivid blue diamond is internally flawless and is the first blue diamond from the De Beers Millennium Jewels Collection to appear at auction. The phenomenal collection was presented by De Beers in 2000 to celebrate the new millennium.

Each of the blue diamonds was specially laser-inscribed with a De Beers Millennium number. The 5.16-carat gem being offered in Hong Kong bears the inscription “De Beers Millennium Jewel 11″. Of the 11 blue diamonds, 9 were graded by the Gemological Institute of America (GIA) as Fancy Vivid, the highest color rating for colored diamonds. This stone is prized for its natural sky blue color and is estimated to bring in between $4.6 million and $5.8 million.

Blue diamonds get their color from the presence of the chemical element boron during the stone’s formation. This stone came from the Premier Diamond Mine of Transvaal, South Africa, the main source of blue diamonds in the world. Out of all the rough diamonds extracted from the Premier Diamond Mine each year, generally only one significant blue diamond can be produced.

Source : luxist