World's largest blue diamond goes on auction block - Value estimated at USD 21 million

The largest blue diamond in the world, appraised at between 21 and 25 million US dollars, will go on auction block next month in Geneva, electronic media have reported.

British auction house Christie's has displayed this 13.22 carat diamond whose exact origin is unknown. Appraisers at Christie's assume it came from South Africa as most of blue diamonds have been discovered there.

- This stone is pure, without any flaws. Simply put, it is the best blue diamond in the world - said Rahul Kadakia, the head of jewelry at Christie's.

Blue diamonds are very rare and account for less than 2 percent of the overall diamond market.

The owner, who had this diamond in his possession for a long time, wanted to stay anonymous. He has decided to sell the stone because he believes he can now get a good price for it.