Akoya Pearl

Akoya pearls are cultured: a technician inserts a shell bead together with a small piece of mantle tissue into the gonad of a host oyster; the tissue forms a sac around the bead and coats it with nacre until harvest. This bead-nucleation method was developed in Japan by Tatsuhei Mise and Tokichi Nishikawa in the early 20th century. Akoya pearls are farmed mainly in Japan, to a lesser extent in China and Vietnam; the traditional product is about 6–7 mm.

A pearl's identity depends on its mollusk and growth environment, not its look. Bead-nucleated Chinese freshwater pearls sold as "Chinese akoya", "baby akoya" or "freshwater akoya" are not akoya pearls, and GIA calls these names misleading; such freshwater pearls often show a very slightly flat side, but visual checks alone are often not enough. Laboratories use X-radiography (a bead cultured pearl shows a central core and surrounding nacre) and trace elements (strontium is typically higher in saltwater pearls, manganese in freshwater pearls). Optically brightened pearls show a stronger bluish fluorescence under long-wave UV than pearls that were only bleached.

Pearl has a Mohs hardness of about 2.5, so it scratches easily. High heat can burn or crack pearls, and many chemicals and all acids, including hair spray, perfume, cosmetics and even perspiration, can damage them. Never use ultrasonic or steam cleaners; wipe the pearls with a very soft, clean cloth after each wearing, use warm soapy water only for occasional cleaning, and let a strung necklace's thread dry completely before wearing it.

Kokichi Mikimoto successfully cultured a pearl in Japan in 1893, and he turned the bead-nucleation technique of Tatsuhei Mise and Tokichi Nishikawa into a major business; Japanese cultured pearls became commercially important in the 1920s, as natural pearl production declined. Japanese akoya output peaked in 1966 at about 148.2 tonnes. In 1996 an oyster disease killed two-thirds of the 300 million shells in Mie, and Chinese freshwater pearls began to compete with akoyas.

Pearl, natural or cultured, is a US birthstone for June and is considered the gem of the third and thirtieth wedding anniversaries. According to GIA, the round shape of some pearls led many cultures to associate pearls with the moon, and in Europe pearls symbolized modesty, chastity and purity.

In ancient China, pearls were believed to guarantee protection from fire and fire-breathing dragons.