It is described as the “the largest round fancy vivid blue diamond ever graded by GIA (Gemological Institute of America)”. It is also part of the Magnificent Jewels and Jadeite Autumn Sale 2013 scheduled to take place on 7 October at the Hong Kong Convention and Exhibition Centre.

According to the sales blurb, the round brilliant cut is rarely used in coloured diamonds due to the high wastage involved in the cutting process, although it is widely applied to white diamonds to maximise brilliance.

“No significant round fancy vivid blue diamond has ever appeared at auction worldwide, thus making the The Premier Blue a rare and exceptional gem,” writes an excited-sounding auction house.

“Sotheby’s has been entrusted with many important blue diamonds and holds the current per-carat price record for fancy vivid blue diamond at auction (with the sale of a 6.01-carat Fancy Vivid Blue Diamond which achieved $1,686,505 per carat in Hong Kong in October 2011),” Quek Chin Yeow, deputy chairman, Asia, and chairman international jewellery, Asia, said.

It should be quite an occasion. Not a bad way to hit 40.