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Keshi Pearl

Can an all-nacre, non-nucleated pearl from a cultivated salt-water oyster or freshwater mussel be called natural?

Gemologists will answer this question with an emphatic “no.” When pressed for reasons, they will argue that any pearl taken from a nucleated mollusk, even one that grew by accident, must be classified as cultured. But evidently the many Arab buyers who pay thousands of dollars for fine-quality, large-specimen strands of these spontaneities think otherwise. If they represent interventions into nature, it is of a divine, not human, kind. “Arabs have never been comfortable with the idea of buying pearls that mollusks were forced to grow,” says Mitsugu Nakanishi of Hikari South Sea Pearl Co., Los Angeles. “But they have no qualms about buying pearls from the same animals when they are a result of chance.”

For years, these chance, or what renowned gemologist Robert Webster called “adventitious,” pearls were known as “seed” pearls because most were very tiny, usually under 2mm. But as the South Seas has become a major producer of chance pearls, many 10mm and more in width and 15mm or more in length, they have become known simply as “keshi.” Because so much supply is taken up by the Islamic world, not many attempts have been made to popularize keshi pearls in this country. The handful of importers who stock them usually don’t even bother to make a domestic market for them. Rather, most view keshi as an exotic departure from the norm of cultured round pearls. But given their rarity, beauty and price, fine keshi deserve immediate elevation from curiosity to connoisseur status.


Unlike the oyster (pinctada martensii) used for saltwater pearl culturing in Japan, both the freshwater mussel (hyriopsis schlegeli) and saltwater oyster (pinctada margaritifera) used for pearl culturing in Japan and the South Seas, respectively, live long enough to be used for up to three pearl-growing cycles. Many of these hardy mollusks that survive their first harvesting tend to grow pearls spontaneously if returned to the waters for a second growing cycle. They don’t even have to be renucleated to produce pearls. (Freshwater mussels are implanted with mantle tissue only while saltwater oysters are implanted with both mantle tissue and bead nuclei.)

According to pearl farmer John Latendresse, American Pearl Co., Camden, Tenn., keshi result when microscopic epithelial cells (that cover body surfaces) dislodge from implanted mantle tissue, find their way to suitable places in the mollusk’s anatomy and there grow renegade pearl sacs. In time, each of these becomes a fully formed pearl.

Ironically, pearl culturers try hard to minimize the possibility of keshi growing in their mollusks, even though they consider them natural and thus rarer than the cultured variety. “There’s only so much nacre that an animal produces,” Latendresse explains. “So the more keshi that grown, the more your cultured pearls are being deprived of nacre.

No wonder then that keshi prevention is a paramount concern at many pearl farms such as those of master pearl grower Nick Paspaley in Australia. Latendresse says Paspaley has slashed the occurrence of keshi to infinitesimal amounts. “On the other hand,” Latendresse adds, “less experienced farms in Tahiti and the Cook Islands (known for black pearls) are producing large numbers of keshi. That’s why you’re seeing so many dark-gray keshi lately.”

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Keshi Pearl