Akoya Cultured Pearls
Definition
A beaded cultured pearl produced in Pinctada fucata, the Akoya pearl oyster. Pinctada fucata is used extensively for pearl culture in Japan, China and other areas. Akoya is the Japanese name for this pearl oyster.
Geographical Situation of the Pearl Farms
Today’s centre of pearl culture in Japan is Kashikojima, from where one can look over the countless small bays with their bamboo rafts on clear days. Until 1938, nearly all cultured pearls came from the Ago Bay or neighboring areas in Mie Prefecture. The prefecture is still the second most important area, and around one third of all pearls come from there. Later in 20 century, Ehime Prefecture was the most important pearl culture area and achieved a slightly higher production than Mie and Kyushu.
Guangxi and Guangdong Province are the main Akoya cultured pearl area in China. There are probably about 2,000 to 4,000 farms in China today. About 60% of the local people along the coasts of Guangxi and Guangdong probably work in the cultured pearl industry today.
Formation of Akoya Cultured Pearl
The implantation of a nucleus is the first stage in the pearl culture process. The time between May and October is considered the most suitable time for operations. In most cases, two nuclei are inserted unless the nucleus is larger than 7mm. sometimes 10 to 20 tiny nuclei are placed into one animal. The outer layer of epithelium cells of the implanted piece of mantle tissue usually survives the insertion process, while the inner layer and the connective tissue are dissolved. The ectoderm is made up of rounded cells,
The formation of the actual pearl sack takes about two weeks at a water temperature of 16degree. The pearl sack grows continuously larger by cell division and surrounds the flowing pearl. The slimy type of skin that is seen when the pearl are harvested is nothing other than the pearl sack.
1.During the grafting process, a nucleus made of mother-of-pearl and a tiny piece of mantle tissue from a donor mollusk are inserted together in such a way that the outer epithelium cells touch the nucleus;
2.The outer epithelium cells of the square of mantle tissue are temporarily replaced with longish, elastic cells, which surround the nucleus, while the endoderm and the connective tissue are dissolved;
3.The rounded epithelium cells appear again and grow into the actual pearl sack; at the same time, they start to secrete pearly substance;
After the nucleus insertion process, the mollusk need up to six weeks in an intensive care station in order to recover. The actual growth time begins after the intensive care period, when the operated mollusks are taken to their allocated destination.
Processing Techniques
After the harvest, pearls which are suitable for sale are initially sorted roughly into three categories (good, medium and low) before they go to the so-called human auctions in Japan. The buyers at the auction are pearl factories, brokers and exporters, who have their own factories.
The factories work the pearls into strings. Drilling is the first step and it is done with small machines. The drill hole starts at both ends and the two holes are supposed to meet in the middle. Drilling is followed by processing which means that the pearls bleached, chemically treated, artificially colored or polished.
After processing, the pearls are sorted according to the grading factors size, shape, color, nacre thickness, luster and surface.
The Quality Factors
Until today, there is no universal grading and evaluation system, although it has been needed for so long. And the original GIA “Pearl Grading System” has become the basis of all pearl grading, it includes the quality factors size, shape, luster, nacre thickness and surface.
Trade terms
The word “necklace” is generally used for pearl necklaces today, although it originally refereed to graded necklace only, in which the centre pearls were distinctly larger than the end pearls.
Prices on the market usually refer to the standard choker length of 40cm, and prices for other lengths are calculated accordingly.
