Akoya pearls come from the akoya oyster. They are usually round in shape and come in a variety of colors from light pink to white to pale yellow with green and blue-gray tones.
Akoya pearls are produced in Japan, China, Korea, Hong Kong, and Sri Lanka. Japan produces large akoya pearls which could measure over 7 mm while the other countries produce smaller akoya pearls.
Keshi pearls are produced in the akoya oyster as well. These are tiny pearls which form spontaneously when a larger nucleated pearl is cultured in the akoya oyster. Keshi pearls do not have a nucleus and are technically "natural pearls." Normally, keshi pearls are three to four millimeters in length.
Akoya pearls can be as small as two millimeters and as large as eleven millimeters in diameter which is the maximum possible size for akoya oysters.