To explain what Japanese Akoya Keshi Pearls are, one must start by explaining what they are not:  Keshi are not found in large quantities but are an extremely rare form of pearl. They are not freshwater pearls, which are harvested by the tons. On the other hand, Keshi are seawater pearls and are found in quantities of under 0.5% of the Akoya cultured pearl production.  Japanese Keshi pearls can occur from 0.6mm to 5mm. As for the south sea and black pearl Keshi can occur in larger sizes. The smaller Keshi are the original Keshi pearls that gave the industry the name of Keshi which in Japanese means poppy seeds. In fact, Keshi are precious because they are the most difficult to find of all pearls.