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Akoya Pearl

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Japanese Akoya Pearl Defined

Japanese Akoya pearls is a term that is often used as a misnomer to describe all cultured akoya pearls. This is no longer an accepted industry term as akoya pearls are now grown in China, South Korea, Vietnam and Australia. Japanese akoya pearls is the correct term for akoya pearls grown in Japan, and is often applied to akoya pearls that have been processed in Japan, regardless of their origin.

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Akoya Pearl Mollusk
Pearl producers cultivate akoya pearls in bivalve molluscs of the genus Pinctada. The main species used in cultivation are Pinctada fucata (particularly the sub-species martensii) and Pinctada chemnizti. Pinctada fucata martensi is native to coastal waters of Japan, while Pinctada chemnitzi is more productive in the Gulf of Tonkin and along the Chinese coast. Currently, most of the akoya pearl producers in China and Japan cultivate by hybridization of the two species.

Cultivated Akoya Pearl Production
Over the past century, Japan has been the undisputed producer of akoya pearls. Japanese akoya pearls have been recognized as a hallmark of classic quality and elegance. Pearliculture of akoya pearls only started 100 years ago with a technique developed by William Saville-Kent and used by Kokichi Mikimoto – the same technique as nuclear insertion is used today.

In the 1990s and through 2007, Japanese akoya pearl producers lost most of their market share due to the booming growth of Chinese producers, at one time producing nearly the same number of akoya pearls. As reported in The International Pearling Journal and the 2006, JCK October Issue Annual Pearl Report, much of China’s production flows through Japan to be marketed as, and mixed with, Japanese akoya pearls*.

The years 2008 and 2009 brought concurrent natural disasters to the akoya pearl region of China, effectively destroying almost all production. Today, China is once again a very small player in the production of akoya pearls, leaving Japan to dominate the market once again.

Characteristics of Akoya Pearl
Akoya pearl oysters, whether Japanese, Chinese or Australian, have the same characteristics. They produce smaller cultured pearls than other saltwater mollusks such as Pinctada margaritafera (black lip pearl oyster) and Pinctada maxima (white lip pearl oyster). Pearl size ranges from 2 to 11 mm, with the most common sizes in the 6 to 8 mm range. When all other factors are equal, the value of akoya pearls increases with size.

Pair of 9 mm akoya pearl earrings
Most akoya pearls are arranged into classic white strands, which gradually add up little by little. For example, single strands can be graduated from 6.5 to 7 mm or from 7 to 7.5 mm. If a strand of akoya pearls is described as a single size, such as 7.5 mm, it is safe to assume the actual size ranges from 7 to 7.5 mm.

Because akoya pearls are beaded and the culture time rarely exceeds two years, the nacre covering the nucleus is relatively thin compared to other saltwater cultured pearls. During the warmer months, nacre deposition is at its peak, but during the colder months, especially in Japan, the metabolism of the akoya pearl oyster drops and deposition slows considerably. The short period after the coolest months of the year is considered the prime time to harvest akoya pearls, as the slower rate of deposition often results in a firmer, glossy, and even three-dimensional sheen.

Akoya Pearl Value Factor
The value of the akoya pearl strand is determined by six quality attributes. When one akoya pearl or strand of akoya pearls scores in the highest category of each excluding size, the pearl or strand of pearls is said to be of “hanadama quality,” or highest quality. But because no two pearls are exactly alike, the range of quality in hanadama does exist.

Akoya pearls usually measure between 2 and 11 mm, while the most common sizes range between 6 and 8 mm. When all other factors are equal, the larger pearl is more valuable.

Akoya pearl oysters are grafted with tiny perfectly round beads, so the akoya pearls are mostly perfectly round. Other shapes such as drops, ovals and even baroque exotic colors do exist but are considered unusual.

Akoya pearls are most often white, with a slight rose or silver tone. However, these colors are rarely natural, as akoya pearls undergo treatments that include maeshori (pre-treatment – ​​increased luster), bleaching (creates a uniform white body color) and pink (organic dyes produce pink undertones).


The naturally occurring body of akoya pearls includes white, silver, silver-blue, yellow and cream, with undertones of pink, silver and green.

A rare natural colored (blue) akoya pearl strand
Akoya pearls are most often valued for their mirror-like luster. Luster is the most important value factor in assessing akoya pearls. A strand that exhibits a strong sheen and few surface stains is considered more valuable than a cleaner strand with a good or bad shine.

The luster value factor contains five categories:
Extraordinary? Reflection looks bright, clear and distinct
Very Good – Reflections appear bright, sharp and almost distinct
Good Reflection looks bright but no different
Fair? Weak reflection and blurry image
Poor? The reflection is dim to nothing and the image is indistinguishable


The term surface is used to assess the surface condition of akoya pearls. While akoya pearls are rarely blemish-free, when other value factors are equal, the fewer visible stains on the pearl’s surface, the higher the grade.

Surface blemishes are not limited to obvious holes, dents and bumps, but also include light or dull spots in pearl reflection or slight inconsistencies such as wrinkles on the surface of the nacre. Any inconsistency of the nacre is considered a defect.

Nacre Quality
The qualities of Nacre are classified into three categories:
Acceptable? the pearl core is invisible and the pearl has no chalky appearance
Core visible? Visible flashes when pearls are rotated and beads are visible
Chalky appearance? Pearls show a clear dull appearance

Reported in Pearl World – The International Pearling Journal, July, August, September Issue, 2006.