Sotheby’s will offer a 93.94-carat Paraiba tourmaline at its upcoming Geneva sale — the largest “top-quality” stone of its kind ever to come to auction, according to the company.

The stone, which is set into a bespoke necklace created by Adler Joailliers, will be one of the star lots in the November 8 Magnificent Jewels and Noble Jewels sale, Sotheby’s said Monday. The auction house expects it to fetch between $1.3 million and $2.5 million.

The necklace, called the Blue Lagoon, features a “waterfall” of round and marquise- and pear-shaped diamonds with a total weight of more than 76 carats, the company noted. It will be offered with the original sketch.

Hailing from Mozambique, the stone is distinguished by “an extraordinary electric blue hue,” which recalls the “crystalline waters of a tropical paradise,” Sotheby’s said. Finding Paraiba tourmalines of this size, with such strong saturation and color, is extremely difficult, the auction house added.

Adler is a family business, created in 1886 by Jacques Adler in Istanbul. His grandsons, Franklin and Carlo, opened a boutique in Geneva in 1972. Since 2015, it has been run by the next generation of Adlers — Allen, who is CEO, and his wife, Daisy, who is chief operating officer.

Image: The Blue Lagoon. (Sotheby’s)