All About Pearls
All About Pearls Tutorial
Natural & Cultivated Pearls
How Pearls are Grown
interesting Pearl Information
Pearls In Religion
Types of Pearls
Pearl Technical Details
Before the beginning of the 20th Century, pearl hunting was the most common way of harvesting pearls. Divers manually pulled oysters from ocean floors and river bottoms and checked them individually for pearls. Not all natural oysters produce pearls. In a haul of three tons, only three or four oysters will produce perfect pearls. Now, however, almost all pearls used for jewelry are cultured by planting a core or nucleus into pearl oysters. The pearls are usually harvested after one year for Akoya, and 2-4 years for Tahitian and South Sea.
This mariculture process was first developed by Tatsuhei Mise Tokishi Nishikawa in Japan, and later perfected by Kokichi Mikimoto, who was granted a patent for the process May 1st, 1916. The nucleus is generally a polished bead made from mussel shell. Along with a small piece of mantle tissue from another mollusk to serve as a catalyst for the pearl sac, it is surgically implanted into the gonad (reproductive organ) of the oyster. South Sea and Tahitian pearl oysters, also known as Pinctada margaritifera and Pinctada maxima, which survive the subsequent surgery to remove the finished pearl are often implanted with a new, larger nucleus as part of the same procedure and then returned to the water for another 2-3 years of growth.
Despite the common misperception, Mikimoto did not patent the process of pearl culture. The accepted process of pearl culture was developed by a team of scientists at Tokyo University between 1907 and 1916. The team was headed by Nishikawa and Tatsuhei Mise. Nishikawa was granted the patent in 1916, and married the daughter of Mikimoto. Mikimoto purchased a right to use the technology from Nishikawa in 1916 or 1917. After the patent was granted in 1916, the technology was immediately commercially applied to Akoya pearl oysters in Japan in 1916. Tatsuhei's brother was the first to produce a commercial crop of pearls in the Akoya oyster. Mitsubishi immediately applied the technology to the south sea pearl oyster in 1917 in the Philippines, and later in Buton, and Palau. Mitsubishi was the first to produce a cultured south sea pearl - although it was not until 1931 that the first small commercial crop of pearls was successfully produced. Pearl culture technology was not applied commercially to the Tahitian black pearl oyster until the 1970's.
The original Japanese cultured pearls, known as Akoya pearls, are produced by a species of small oysters, Pinctada fucata, no bigger than 6 to 7 cm in size, hence Japanese pearls larger than 10 mm in diameter are extremely rare and highly prized. In the past couple of decades, cultured pearls have been produced with larger oysters in the south Pacific and Indian Ocean. One of the largest pearl-bearing oysters is the Pinctada maxima, which is roughly the size of a dinner plate. South Sea pearls are characterized by their large size and silvery color. Sizes up to 14 mm in diameter are not uncommon.
Australia is one of the most important sources of South Sea pearls. Tahitian pearls (also referred to as Tahitian pearls) are also another South Sea pearl. Mitsubishi commenced pearl culture with the south sea pearl oyster in 1916 as soon as the technology patent was commercialized. By 1931 this project was showing signs of success, but was upset by the death of Tatsuhei. Although the project was recommenced after Tatsuhei's death, the project was discontinued at the beginning of WW11 before significant productions of pearls were achieved. After WW11, new south sea pearl projects were commenced in the early 1950's in Burma and Kuri Bay and Port Essington in Australia. Japanese companies were involved in all projects using technicians from the original Mitsubishi south sea pre-war projects. Despite often being described as black south sea pearls, Tahitian pearls are not south sea pearls. The correct definition of a south sea pearl is "the pearl produced by the pinctada maxima pearl oyster."
In 1914, pearl farmers began culturing freshwater pearls using the pearl mussels native to Lake Biwa. This lake, the largest and most ancient in Japan, lies near the city of Kyoto. The extensive and successful use of the Biwa Pearl Mussel is reflected in the name Biwa pearls, a phrase which was at one time nearly synonymous with freshwater pearls in general. Since the time of peak production in 1971, when Biwa pearl farmers produced six tons of cultured pearls, pollution and over harvesting have caused the virtual extinction of this animal. Japanese pearl farmers now culture a hybrid pearl mussel - a cross between the last remaining Biwa Pearl Mussels and a closely related species from China - in other Japanese lakes such as lake Kasumi Ga Ura.
In the 1990s, Japanese pearl producers also invested in producing cultured pearls with freshwater mussels in the region of Shanghai, China, and in Fiji. Freshwater pearls are characterized by the reflection of rainbow colors in the luster. Cultured pearls are also produced using abalone.