Chen purchased the diamond May 28 at Christie’s Hong Kong Magnificent Jewels sale for more than $11.15 million, $148,000 per carat, a world record for a briolette diamond sold at auction.

Auctioneer Christie’s sold a 75.36 carat briolette diamond for $11 million in Hong Kong during a sale Tuesday. The sum set a new record for that particular style of gem — an elongated pear ...