Keshi pearls are created accidentally by the mollusk. It is either a second growth byproduct after a nucleated pearl has matured or grown after a nucleus is rejected by the mollusk. They are total nacre.

(You remember that a saltwater pearl is started by inserting a round nucleus into the gonad muscle of the oyster with a piece of mantle tissue to activate the production of nacre around the nucleus.)

It is actually not far off to call Keshi pearls, "pearls gone wild". 

The designation of Keshi was accepted in 1998, not too long ago. Keshi means "poppy seed" in Japanese and the first Keshi were tiny pearls. They weren't too popular at first, but in recent years, they have grown in desirability with the increase in size.

The first Keshi were discovered in Akoya oysters (Pinctada fucata), which are smaller oysters about 8" across. Recently they have been found in South Sea (Pinctada maxima) and Tahitian oysters (Pinctada margaritifera), which are massive oysters up to 36" across. Because of the larger shell, the Keshi are larger.

They are popular today for their irregular shapes and superior luster, but this also brings high price points. They are stunning. These are South Sea and Tahitian pearls that are entirely nacre. How deep is that luster? Because they are all nacre, the reflection of light goes entirely through the pearl.

Keshi pearls are luxurious and all natural. They are a perfect complement for the pearl obsessed to create a fresh and individual look.