By Georgia McCafferty , for CNN Written by

An extremely rare 15.38 carat pear-shaped pink diamond -- called the 'Unique Pink' -- sold for $31.6 million at Sotheby's in Geneva on Tuesday, making it the most expensive fancy vivid pink diamond ever to sell at auction.

The spectacular diamond, set in a simple ring, sold to an Asian private buyer who bid for the rare gem over the telephone. A Sotheby's spokesperson said they were not yet able to reveal the buyer's identity.

































1 / 17 The "Aurora Green" is the largest Fancy Vivid green diamond ever sold at auction. The stone went under the hammer on May 31, 2016 at Christie's auction house in Hong Kong, selling for $16,818,983. Credit: courtesy christies

"It is difficult to imagine a diamond that better illustrates the term vivid pink than this outstanding stone...the color is simply astonishing," David Bennett, worldwide chairman of Sotheby's International Jewellery, said in a statement announcing the sale.

Sparkling record breakers

The most expensive pink diamond ever to sell at auction remains the 24.78 carat 'Graff Pink,' which sold for $46.2 million at Sotheby's in November 2010.

However, yesterday's 'Unique Pink' sale eclipsed the previous record for a fancy vivid pink diamond, set by the 'Sweet Josephine' at a Christie's auction in November 2015.

That 16.08 carat diamond sold for $28.5 million to Hong Kong billionaire, Joseph Lau, who purchased it for his then 7-year-old daughter, Josephine.

As colorful as these diamonds may be, they pale in comparison to the diamond Lau purchased for his daughter at a Sotheby's auction the very next day.

Why are diamonds such an emotional purchase?

That 12.03 carat blue sparkler, dubbed the " Blue Moon of Josephine ", sold for an eye-watering $48.4 million, making it the world's most expensive diamond ever.

But that record may soon be challenged, with the 14.62 carat 'Oppenheimer Blue' -- the world's largest vivid blue diamond ever to be sold at auction -- going under the hammer at a Christie's auction in Geneva on Wednesday night.