On October 7, Sotheby’s Hong Kong will offer one of the world’s most exquisite examples of grey-pearl jewelry for auction. A necklace and a pair of ear clips, known as the Cowdray Pearls, are estimated to fetch between $4.5 million and $7 million when offered as part of the Magnificent Jewels and Jadeite autumn sale at the Hong Kong Convention and Exhibition Centre.

Culled from the collection of the English noblewoman and avid pearl collector Viscountess Cowdray (Lady Pearson), the necklace was hand-strung and mounted by Cartier, and features 42 rare, natural, grey saltwater pearls, ranging from brown to gray with varying rosé, purple, and green overtones. The piece is accompanied by a pair of natural grey-pearl ear clips, also mounted by Cartier. Both designs will be exhibited in New York, London, Geneva, the Middle East, Singapore, and Taipei, Taiwan, before crossing the block in Hong Kong next month.

As the effects of overfishing and ocean pollution continue to threaten oysters and mollusks (and, by extension, the number of high-quality natural pearls they can produce), vintage examples are selling feverishly at auction for record prices. In May of this year, Sotheby’s sold a natural-pearl-and-diamond necklace for nearly $4 million, more than seven times its estimated price; in 2013, the auction house dropped the hammer on another natural-pearl necklace for more than $5.5 million—more than double its pre-auction estimate. But neither of these remarkable trades compare to Sotheby’s record-setting sale of a $7 million, double-row, natural-saltwater-pearl necklace earlier this summer. If this booming demand continues, the Cowdray Pearls may be Sotheby’s next coup de grâce. (sothebys.com)