The "Bulgari Laguna Blu," an 11.16-carat fancy vivid blue diamond, is expected to fetch upwards of $28 million at Sotheby's Magnificent Jewels and Noble Jewels auction in Geneva on May 16.

The auction's pear-shaped headliner ranks among the finest blue diamonds to have hit the auction scene over the past two decades, and joins an elite club that includes the 15.1-carat “De Beers Cullinan Blue” ($57.5 million, Sotheby's Hong Kong, 2022), the 14.6-carat “Oppenheimer Blue” ($57.5 million, Christie’s Geneva, 2016) and the 12.03-carat “Blue Moon of Josephine” ($48.5 million, Sotheby's Geneva, 2015).

Boasting a VS1 clarity and a color intensity that's been described by Sotheby's as “extraordinary” and “mesmerizing,” the Bulgari Laguna Blu was originally set in a ring by the Italian designer in the early 1970s and sold to a prestigious European collection later that same decade. It remained largely out of the spotlight for the next 44+ years.

All that changed when it was worn by Indian actress and former Miss World Priyanka Chopra for the Met Gala fashion show in New York on Monday. Instead of being set as a ring, the blue diamond became the centerpiece of a lavish diamond necklace, also designed by Bulgari.

Blue diamonds are considered one of the rarest colors of all diamonds. A fabulous fluke of nature, a blue diamond owes its color to the random presence of boron within the diamond’s carbon structure.

Scientists believe that blue diamonds form about 400 miles below the surface, four times deeper than about 99 percent of all other diamonds.

The extreme rarity of the Bulgari Laguna Blu is apparent on many levels.

First, this gem earned the highest color grade ever assigned to a blue diamond by the Gemological Institute of America (GIA). The organization graded it fancy vivid blue with no secondary color present. Fewer than 1% of blue diamonds earn the "vivid" rating.

Next, while blue diamonds make up less than 0.02% of mined diamonds, those weighing more than 10 carats are among the rarest of the rare.

According to Olivier Wagner, head of jewelry at Sotheby’s Geneva, the Bulgari Laguna Blu ranks as the third-largest pear-shaped fancy vivid blue diamond to come to auction. It's also reported to be the most valuable piece ever sold by Bulgari.

Sotheby's emphasized that the Bulgari Laguna Blu has remained in the same family ever since its acquisition in the 1970s and that the stone has been unmodified, even though modern diamond cutting technology could have been employed to enhance the diamond's characteristics and increase its value.

After making its New York debut at the Met Gala, the Bulgari Laguna Blu will be heading to the Mandarin Oriental in Geneva, where it will be on exhibit, starting May 11 in the lead-up to the main event five days later.

Credits: Images courtesy of Sotheby's.