Bleu Royal, the largest internally flawless fancy vivid blue diamond ever seen at auction will come up at Christie’s in Geneva on November 7. Fancy vivid blue diamonds of over 10 carats are practically unheard of in the saleroom. Only three have come up in more than 250 years at Christie’s. This 17.61 carat pear shaped stone combines a rich colour and flawless purity. In the same collection for the past 50 years it remains among the rarest to have been unearthed. Prices for top quality coloured diamonds have increased exponentially in recent years. The estimate is $35 million – $50 million (€32.8 million – €46.8 million). UPDATE: THIS SOLD FOR $43.8 million.