Rare blue diamond sells for record $48.5 million

GENEVA -- Sotheby's says a rare blue diamond has sold for a record $48.5 million at a Geneva auction, including fees.

The 12.03-carat "Blue Moon" diamond, set in a ring, is said to be among the largest known fancy vivid blue diamonds and was the showpiece gem at Wednesday's auction in Geneva. The price fell within the pre-auction estimate of $35 million to $55 million. A packed auction room broke into applause after the hammer came down at a price of 43.2 million Swiss francs, excluding fees.

The Blue Moon -- in reference to its rarity, playing off the expression "once in a blue moon" -- topped the previous record of $46.2 million set five years ago by The Graff Pink.

Sotheby's said it was bought by a Hong Kong private collector and promptly renamed "The Blue Moon of Josephine" -- a similar name to one given to a pink diamond ring that sold for $28.5 million a day earlier, "Sweet Josephine."

That too was bought by a Hong Kong collector who was not publicly identified.

A Sotheby's spokeswoman was not available for comment.

The polished blue gem was cut from a 29.6-carat diamond discovered last year in South Africa's Cullinan mine, which also yielded the 530-carat Star of Africa blue diamond in the British crown jewels.

Sotheby's said experts took five months for an "intense study" of the original diamond, and a master cutter took another three months to craft, cut and polish the stone. The auction house said in a video the Cullinan mine was the "only reliable source in the world for blue diamonds," and only a tiny percentage of those found in it contain a trace of blue.

Blue diamonds are formed when boron is mixed with carbon when the gem is created.