Akoya is the Japanese name for the oyster, Pinctada fucata (Gould, 1857). Also know as Saltwater Pearls, the Akoya Oyster produces the pearl that most of us think of when we talk of Pearls.

This pearl generally is 10mm and smaller. It is more commonly seen in smaller sizes. The natural colors of the Akoya Pearl are light pink (rose) to white with silver overtones to somewhat yellowish.

The Akoya Pearl is also typically round.

One of the reasons that Akoya Pearls are more valuable has to do with supply and demand. So while the method of cultivating freshwater or saltwater pearls is the same the differences consist mainly in the two different mollusks. The mussel that is used in freshwater pearl cultivation can produce up to 50 pearls at one time, the akoya or saltwater pearl can produce only up to two pearls at a time. Freshwater pearl cultivation consists of the insertion of a piece of soft tissue only. The cutivation of saltwater pearls requires that a shell bead nucleus plus a piece of soft mantle be inserted into the oyster. The insertion of the shell bead is one reason why so many Akoya Oysters will either reject the surgical implant or die. Following this only about 33% will actually produce a pearl. And then only a tiny percentage of these will produce a pearl of any value.So this is the reason why costs of production are so much greater in Akoya Pearls than in Freshwater pearls. And this reflects why Akoya Pearls are more valuable than the freshwater pearl. Investment grade is a term more likely to be applied to the Akoya Pearl than it is to the freshwater pearl. And it is true. If you are looking for an heirloom or an investment then you would be thinking of purchasing a piece of Akoya Pearl Jewelry.

After supply and demand is the pearl itself, roundness and shape are very important to the value of the pearl because, the mantle, that is inserted into the freshwater pearl, is generally not round, the peal from a freshwater pearl is more likely to be unusual in shape. Indeed, this is why Freshwater Pearls were called " rice krispies". That is how the Freshwater pearls look that were produced by China. Since they first started production China's Freshwater pearl quality has definitely improved.

So shape considered the single most important reason why the Akoya is more valuable than the Freshwater pearl is quantity. The freshwater mussel that produces the freshwater pearl can produce up to 50 pearls per mussel, and the Oyster that produces the Akoya Pearl can produce only 1 or 2 pearls at a time.

http://www.fieldmuseum.org/pearls/

http://www.pbs.org/wgbh/nova/pearl/