The Akoya Pearl Mollusk
Pearl producers cultivate akoya pearls in a bivalve mollusk of the Pinctada genus. The primary species used in cultivation are the Pinctada fucata (specifically the sub-species martensii) and the Pinctada chemnizti. The Pinctada fucata martensi is native to the coastal waters of Japan, while the Pinctada chemnitzi is more prolific in the Gulf of Tonkin and along the coast of China. Today, most akoya pearl producers in both China and Japan cultivate with a hybridization of the two species.
Production of Cultured Akoya Pearls
For the last century, Japan has been the undisputed champion producer of akoya pearls. Japanese akoya pearls have been known as the hallmark of classic quality and grace. Pearliculture of akoya pearls only began 100 years ago with the technique developed by William Saville-Kent and used by Kokichi Mikimoto - the same technique of nucleus insertion used today.
In the 1990's and until 2007, Japanese akoya pearl producers lost much of their market share to a surge in growth of Chinese producers, at one time producing nearly the same quantity of akoya pearls. As reported in The International Pearling Journal and the 2006, JCK October Issue Annual Pearl Report, much of Chinese production flowed through Japan to be marketed as, and mixed with, Japanese akoya pearls*.
The years 2008 and 2009 brought concurrent natural disasters to the akoya pearling regions of China, effectively destroying nearly all production. Today, China is once again a very small player in akoya pearl production, leaving the Japanese to dominate the market once again.
Characteristics of Akoya Pearls
Akoya pearl oysters, whether Japanese, Chinese or Australian, share the same characteristics. They produce smaller cultured pearls than other saltwater mollusks such as the Pinctada margaritafera (black-lip pearl oyster) and the Pinctada maxima (white-lip pearl oyster). The pearls range in size 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 rises with size.
Most akoya pearls are composed into classic white strands, which graduate slightly by half-millimeter increments. For example, a single strand may graduate 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 bead nucleated and culturing time rarely exceeds two years, the nacre covering the nucleus is quite thin relative 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 is slowed considerably. The short period after the coolest months of the year is considered the prime time to harvest akoya pearls, as the slowed deposition rate often results in tighter, glossy and even three-dimensional luster.
Value Factors of Akoya Pearls
The value of a strand of Japanese or Chinese akoya pearls is determined by six quality attributes. When a single akoya pearl or a strand of akoya pearls score 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 as no two pearls are exactly identical, a quality range within hanadama does exist. The designation of hanadama is typically reserved for Japanese akoya pearls.
Akoya pearls typically range in size from 2 to 11 mm, while the most common sizes fall between 6 and 8 mm. When all other factors are considered to be equal, larger pearls are more valuable.
Akoya pearls are mostly round, while some drops, ovals and even exotic-colored baroques do reach the market. In most cases, perfectly round akoya pearls are more valued.
Akoya pearls are most often white, with a slight rose or silver overtone. These colors are rarely natural, however, as akoya pearls are subjected to treatments which include maeshori (pre-treatment -- luster enhancement), bleaching (creating a uniform white body color) and pinking (organic dye resulting in a pink overtone).
Naturally occurring akoya pearl body colors include white, silver, silver-blue, yellow and cream, with secondary overtones of pink, silver and green.
Akoya pearls are most often prized for their mirror-like luster. Luster is the most important value factor in grading akoya pearls. A strand exhibiting strong luster and some surface blemishing is considered more valuable than a cleaner strand with fair or poor luster.
The luster value factor contains five categories:
- Excellent – Reflections appear bright, crisp and distinct
- Very Good -- Reflections appear bright, crisp and nearly distinct
- Good – Reflections appear to be bright but not distinct
- Fair – Reflections are weak and images blur
- Poor – Reflections are dim to non-existent and images cannot be made distinguished
The term surface is used to rate the surface condition of an akoya pearl. While akoya pearls are rarely blemish-free, when other value factors are equal, the fewer visible blemishes that are on the surface of the pearl, the higher the value.
Surface blemishes are not limited to obvious pits, dents and bumps, but also include light or dull spots within the reflection of the pearl or slight inconsistencies such as wrinkles on the surface of the nacre. Any inconsistency of the nacre is considered a blemish.
Nacre quality is classified into three categories:
- Acceptable – the nucleus of the pearl is not visible and the pearl has no chalky appearance
- Nucleus visible – Blinking is visible when the pearl is rotated and the bead is noticeable
- Chalky appearance – The pearl shows an obvious dull appearance
* Reported in Pearl World - The International Pearling Journal, July, August, September Edition, 2006.
** 2006, JCK October Issue Annual Pearl Report - Page 88 - Japanese/Chinese Akoyas
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