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Japanese Pearl Farms: Akoya, Biwa & Keshii Pearls

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History of Japanese Pearl Production

Before the beginning of the 20th Century, pearl hunting or diving was the most common way of harvesting pearls. Japanese pearl divers had to manually pull oysters from ocean floor, and check them individually for pearls.

Around 1914, Japanese pearl farmers began culturing saltwater and freshwater pearls, eventually spreading their knowledge throughout the South Seas. Since that time, the Japanese have dominated the cultured pearl industry, pioneering many of the technological advancements in seed nucleation, harvesting, and oyster breeding. Pearl culturing in Japan is carried out predominantly by small-scale cooperatives, with few large-scale operations.

Freshwater Pearls from Lake Biwa-ko

Freshwater pearls were cultured using the pearl mussels native to Lake Biwa (below). The largest and most ancient lake in Japan, Lake Biwa (aka Lake Biwako) is located to the north of the city of Kyoto, in the Shiga prefecture. The widespread use of the 'Biwako Pearl Mussel' Hyriopsis schlegeli is reflected in the generic use of the name "Biwa pearls," and the name has now become synonymous with freshwater pearls in general.

Lake Biwa Okinoshima Island

Lake Biwa's Okinoshima Island (Photo: Public Domain)

   Roman Necklace

Shiga prefecture Estuary (Photo: Public Domain)

Lake Biwako is fed by nearly 500 rivers that originate in the surrounding Hira, Ibuki, and Suzuka, mountains. During the peak production period of Biwa pearls in the 1970s, Biwako pearl farmers produced six tons of freshwater cultured pearls (FWCPs) per year. Since that time, pollution, a devastating freshwater red algae bloom (red tide), and over-harvesting have caused the virtual extinction of the Biwa Hyriopsis schlegeli pearl mussel. Japanese pearl farmers now culture a hybrid pearl mussel which is a cross-breed between the last remaining Biwa Pearl mussels and a closely related species from China.

Freshwater Pearls from Lake Kasumigaura

The Lake Kasumigaura (Kasumiga-ura) region is a relatively new pearl cultivation area, started in the 1990s. Lake Kasumigaura, located 70 km north-east of Tokyo, in the Ibaraki Prefecture, is the second largest lake in Japan. Pearls cultured at the Kasumigaura Pearl Farm are known for their pink or rosy hues, and high luster due to a four year cultivation period.

Pearls from the Lake Kasumigaura region are sold under the name of "Kasumiga Pearls" similar to the way in which "Biwa pearls" were branded nearly 100 years ago. For pearl cultivation, this region has used a hybrid mussel which was a cross between Hyriopsis cumingii, which is a Chinese freshwater mussel species, and H. schlegeli (Ikecho-gai) which is native to Lake Biwa [6].

Japanese Akoya Saltwater Pearls

The original Japanese cultured pearls, known as Akoya (or saltwater) pearls, were produced by a species of small akoya oyster (Pinctada fucata) no larger than 6 to 7 centimeters in size. These small Akoya pearls tend to a thinner nacre coating, and like their freshwater cousins, they may be treated to improve color. Japanese pearls larger than 10mm in diameter are extremely rare and highly prized.

Mikimoto Pearls

One of the pioneers in Japanese cultured pearl production was Kokichi Mikimoto. Mikimoto was born in Toba City, Japan on March 10, 1858, and began raising oysters in 1888, on Ojima Island, now named 'Mikimoto Pearl Island,' and on Ago Bay located in south-eastern Mie prefecture. Ago Bay is situated along the rugged coastline known as the Rias coast. Other major pearl producing areas of Japan are in the Ehime, Kumamoto, Oita and Nagasaki prefectures.

By the late 1890s Kokichi Mikimoto had been awarded a patent for the process of culturing hemispherical pearls or "Mabes." Over the next 20 years, he continued his research into the art of culturing pearls, which by the early 1900's lead to his acquisition of a patent for culturing "Spherical" or "Round" pearls.

Japanese Pearl Production

Japanese Pearl Farms in Ago Bay (Photos: Public Domain)

In the early 1900s, Mikimoto, along with Sukeo and Masayo Fujita, and Kichiro Takashima adapted their knowledge of silver-lipped oyster pearl cultivation to the blacklip Pinctada margaritifera South Sea pearl oyster. In 1914, Mikimoto established black-pearl farms along Kannonzaki Point, Kabira bay, and Nakura Bay on Ishigaki Island, in Okinawa prefecture. In 1922 he spread his operations to the South Pacific island of Palau, creating silver-lipped South Pacific pearls.

In 1927, Kokichi Mikimoto met inventor and pearl collector, Thomas Edison in New York, Edison declared "There are two things which couldn't be made at my laboratory, diamonds and pearls." Of coarse Edison was wrong about diamonds, but pearls have yet to be simulated in a laboratory.

Japanese Pearl Production

Japanese Akoya Pearl Production (Photos: Public Domain)

Mikimoto passed away on September 21, 1954 at the age of 96, but his legacy lives on today. Posthumously he was awarded the Grand Cordon of the Order of the Sacred Treasure. In 1899 the first Mikimoto pearl shop was opened in the fashionable Ginza district of Tokyo.

Mikimoto discovered a technique for inducing the creation of a round pearl within the oyster's tissue. This discovery revolutionized the pearl industry. For the first time, pearl farmers could cultivate large numbers of high-quality round pearls. This was in stark contrast to the traditional method of harvesting natural pearls, which are difficult to find and have an unpredictably wide variety of shapes, sizes, quality levels.

Bibliography & Suggestions for Further Study on Japanese Pearls

1. Pearl Guide, Japanese Akoya Pearls .

2. K Mikimoto & Co, Ltd, Pearls .

3. Seikai National Fisheries, Pinctada margaritifera Cultured in Okinawa .

4. American Museum of Natural History, Pearls .

5. U.N. Food & Agriculture Org., Pearl Oyster Taxonomy & Distribution .

6. NIES, Hybridization Between Species of Freshwater Pearl Mussels .

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