Regardless of the species, the quality
of pearls is rated according to size,shape,
nacre thickness, surface, color and luster.
The quality of Akoya cultured pearl is rated as
follows regarding these characteristics


The sizes of Akoya cultured pearls range from 2 to 10mm. Pearls with sizes from 5 to 8mm are generally used for necklaces. On the other hand, any size can be used for ornaments. Because of this size variety, Akoya cultured pearls can satisfy the wishes of practically any customer.  
Those who look for a gorgeous accessory will find satisfaction in a 9mm pearl necklace. Young women in the work force can accent their beauty with a simple 5mm choker. Because of size variety, there is an ideal Akoya cultured pearl for every time, place and occasion.


When it comes to shape, no other cultured pearl can compete with the Japanese Akoya cultured pearl. To be sure, drop, pear and baroque shaped pearls are attractive, but the basic shape is round. For Akoya cultured pearls, round had been designated as the most important shape, followed by semi-round, semi-baroque and baroque.  
Although this is not the case with other pearls, if an Akoya cultured pearl has extreme circles, it is never accepted unless its beauty can be otherwise evaluated.

Nacre thickness

Nacre thickness is more than the amount of nacre; it has other meaningful aspects as well. The structure of the nacre is composed of thousands of layers of thin calcium carbonate crystals with the thickness of 0.35 to 0.5 μm (1μm = 1/1000mm). This distinctive nacre structure influences the color, luster, durability and elasticity of the pearl.  
Nor is it an exaggeration to say that many of the unique characteristics of the Akoya cultured pearl are attributable to its nacre structure. 


All the factors that disturb the surface smoothness of the pearl and hence decide its appearance are called blemishes. The value of the pearl is greatly affected by these blemishes. Generally, the degree of blemish is divided into clean, slight spot, medium spot and heavy spot according to number, size, kind and location of the blemish. Blemishes are divided into two kinds, natural and artificial.  
Natural blemish is formed during pearl cultivation. Artificial blemish, on the other hand, is mainly the result of processing and it is rejected at Pearl Export Inspection. 


Luster is probably the best expression of a pearl's beauty. Luster does not simply mean a shiny surface: it implies the structural beauty of the nacre. Japanese Akoya cultured pearls have a special luster which mainly comes from seasonal changes. They are grown in the sea where the water temperature is comparatively low and varies according to the season. These seasonal changes compact the aragonite crystals. Crystals that are formed in the water produce beautiful color and fine luster.  
Therefore, when Japanese Akoya pearls have enough nacre and contain the ideal amount of aragonite crystals, they are said to be the most beautiful and lustrous among pearls. 


The main colors of Akoya cultured pearls are white, silver, rose pink and pink, and cream, gold, green and blue follow. The deep hue of the Japanese Akoya pearls derives from their characteristic nacre structure. Some Akoya cultured pearls undergo certain processes to extract the latent beauty of the pearl.  
Of course both cultivators and researchers also make their utmost effort to produce Akoya pearls with good color by improving oyster quality, culturing technique and harmonization with farm circumstances.
For further information, please contact:
Japan Pearl Exporters'Association 
Japan Pearl Center
122, Higashi-machi,Chuo-ku,Kobe,650-0031,JAPAN
Tel:078(331)4031 Fax:078(331)4345