April’s birthstone is diamond, but after this month, the powers that be may want to change it to blue diamond.

On April 24, a 5.3 ct. fancy deep-blue diamond sold for $9.6 million at Bonhams’ Fine Jewellery sale in London—setting a record $1.8 million per-carat price for a diamond that color.

The buyer was London-based Graff Diamonds. The jewel—set in a Trombino ring made by Bulgari—is set horizontally within a mount pavé-set with brilliant-cut diamonds and baguette-cut diamonds. The circa-1965 piece had been estimated to fetch $1.3 million–$1.9 million.

“We are delighted with the price,” Jean Ghika, director of Bonhams jewelry department for Europe, said in a statement. “It was a sensational stone which charmed everyone who viewed it prior to the sale.”

JCK