The word 'Keshi' means 'poppy seed' in Japanese and these pearls are also sometimes referred to as seed pearls.
There is considerable controversy as to the classification of whether Keshi pearls are natural pearls or cultured pearls. It is impossible to determine the difference in the laboratory.
As a basic rule, if the oyster has been seeded by human intervention and an additional pearl (by-product) is created through the provocation of any substance, the pearl is considered to be cultured and is therefore called a “Keshi” pearl and is 100% nacre.
They are generally small in size and their shapes vary widely. Keshi come in a wide variety of colours and tend to have a high lustre. Most common today are the South Sea and Tahitian Keshi pearls.