The world’s largest blue diamond ever to come to auction has sold for 450,925,000 HKD, or $57.5 million.

Named “The De Beers Cullinan Blue,” the massive 15.10-carat step-cut gem sold at Sotheby’s in Hong Kong after an eight-minute bidding war among four hopeful buyers, according to Sotheby’s. The winning bid, which surpassed its high estimate of $48 million, came from an anonymous buyer by telephone.

According to a statement from Sotheby’s, the Gemological Institute of America (GIA) categorized the jewel as “fancy vivid blue” — the top color grading, which has been awarded to no more than 1% of blue diamonds submitted to the organization.

Describing the diamond as “exceptionally rare,” the Sotheby’s statement added that only five gems over 10 carats have ever appeared at auction. None have ever been over 15 carats, “making the appearance of this flawless gem a landmark event in itself.”

With a final price of $57,471,960, The De Beers Cullinan Blue just narrowly missed setting the record for the most expensive blue diamond ever to sell at auction. That title is still held by the 14.62-carat “Oppenheimer Blue,” which sold in 2016 with a final price of $57,541,779, a difference of just under $70,000.

Patti Wong, chairman of Sotheby’s Asia, said in a statement: “It is truly a once-in-a-generation stone, and quite simply the greatest blue diamond of its size I have ever seen.”