A rare blue diamond just sold for $44 million at a Christie's auction

• A rare blue diamond set in a ring sold for $43.8 million at a Christie's auction in Geneva.
• Christie's said that the 17.61-carat diamond, the Bleu Royal, is among the rarest to exist.

A rare blue diamond set in a ring sold for 39.505 million Swiss franc ($43.8 million) at a Christie's auction in Geneva on Tuesday.

The 17.61-carat Bleu Royal diamond is pear-shaped and is described as a "Fancy Vivid Blue" gem.

"Large, vivid fancy color diamonds are extremely rare and very valuable," according to the Gemological Institute of America (GIA).

The gem is around 0.84 inches at its longest point and is "internally flawless," according to a report by the GIA.

It's set in 18-carat rose gold alongside two smaller diamonds of 3.12 and 3.07 carats.

Christie's had set an estimate price of between $35 million and $50 million.

Christie's said that the Bleu Royal is among "the rarest to have been unearthed" and is "the largest Internally Flawless Fancy Vivid Blue gem ever to appear for sale in auction history."

Prior to the sale of the Bleu Royal, only three fancy vivid blue diamonds of more than 10 carats had even been sold at Christie's in its over 250-year history, the auction house said, with the most expensive of these – the 14.62-carat Oppenheimer Blue – selling for $57.5 million in 2016.

It said that the Bleu Royal has been in a private collection for the past 50 years and that Tuesday's sale was the first time it was presented at auction.

In total, the Magnificent Jewels auction in Geneva – which included brooches, clocks, and a Cartier tiara from around 1955 – brought in 69.9 million Swiss franc (or $77.6 million).