Cultivation of the Conch Pearl: A Comparison to Natural & What the Future Holds

Elisabeth Strack

Natural pearls

The bulk of production comes from two closely related marine genera, named Pinctada and Pteria. The classical finding places still produce and the natural pearl market still exists, even going through a type of revival.

Pearls from other bivalve genera do usually not have the nacreous structure of pearls from Pinctada and Pteria but show instead an arrangement of prismatic crystals. They lack iridescence, described as "orient" or "lustre", one of the prerequisites for the definition of a pearl. They are referred to as "non-nacreous" pearls and have developed into a new market that has created its own demand.

The white Tridanca pearls from the bivalve Tridacna gigas, the giant clam, reach sizes of 20mm and more, they show a type of flame structure. The Sulu Sea seems to be a favourite finding place.

Pecten pearls from the Gulf of California in Mexico come from the bivalve Nodipecten subnodosus, the so-called Lyon’s Paw shell.

Colours go from white to brown and purple shades, there is no distinct lustre.

Quahog pearls from Mercenaria mercenaria, the so-called wampum or quahog shell of the Indians, show blue-violetish colours, mixed with white,  in combination with a porcelain-like lustre.

While all marine gastropods can produce pearls, only a few genera have reached fame. Among them are Abalone pearls in striking bluish-green colours from different species of the gastropod Haliotis, pink Conch pearls from Strombus gigas in the Caribbean Sea and orange Melo pearls from the bailer shell Melo melo in the South China Sea. Pearls from the Turbo and Cassis genera are absolute novelties and have never been seen on the market before.

While culturing of Abalone pearls started as early as in 1897 in France, only New Zealand companies have been successful since 1995 with  Mabe pearls. In 2009 it became known that scientists of the Harbor Branch Oceonographic Instiution in Ft. Pierce, Florida were successful in producing cultured Conch pearls.

The cultured pearl industry

Japan

Akoya cultured pearls (called Akoyas in short), White South Sea Cultured pearls and Black South Sea cultured pearls make up the bulk of pearl production while Mexican cultured pearls, produced with Pteria sterna, occupy a niche. In addition, there is an enormous amount of freshwater cultured pearls on the market that mainly, with the negligible exception of pearls from Lake Kasumigaura in Japan, come from China and are produced with a freshwater mussel  of the genus Hyriopsis Conrad 1853.

While the world production of all marine cultured pearls together amounts to not more than 40 tons per year, China produces about 1.500 tons, reaching however a total value of only about

150 million dollar. The value of marine production amounts to more than the double, approximately 325 million dollar.

Akoya cultured pearls

Japan started its pearl production in 1916 and was for decades not only the leading producer but controlled the world market.  After a heavy crisis around 1996 when hundreds of millions of its local Pinctada martensii molluscs died, yearly production went down drastically. In 2009 it was only around 12 tons while in 1995 it had still amounted to 60 tons.  The crisis may have been due to the fact that molluscs were weak because they were artificially bred in hatchery stations. Japan started to import Pinctada chemnitzii from China, both from natural occurrences and from hatcheries, and either used it  on its own or cross-bred it with the Japanese species. 

The crisis had its good aspects as it made farmers more considerate about the environment and it led to an improvement in quality and a concentration on larger pearl sizes in the range of 8-9.5mm.

A distinct novelty

At the Hong Kong fair of September 2009, Japanese exhibitors showed for the first time large, baroque  bluish-grey Akoya pearls in sizes of up to 12mm.  The pearls had a  metallic lustre and an extraordinary orient. The Tanabe Pearl Farm in Mie Prefecture was the first to disclose that the stunning colours were produced by feeding molluscs with a liquid that contains proteins bearing colouring agents. It is not quite clear if those agents are organic pigments similar to carotene or if they are metallic compounds. Information so far is controversial but the CIBJO Pearl Commission has already shown action and decided that the pearls have to be described as "colour-induced." The new definition to include into the Pearl Book is:  "A treatment inducing colouration of the cultured pearl by injection into the pearl sack during the cultivation process."

It is interesting to note in this  context that the Mikimoto company has announced in 2009 that it is carrying out experiments on the coast of Fukuoka Prefecture on Kyushu Island, by using naturally occurring Pinctada martensii.

China

China’s own Akoya production started  in 1958 but it remained unknown to the world market till 1992. Between 1996 and 2001 production reached 20-25 tons per year. Hurricanes in 2007 and 2008 dealt a nearly fatal blow to many pearl farms and production figures are probably below those for Japan today. It is difficult to find reliable information.

Production areas stretch along the southern coast of China from the border with Vietnam to Shantou. Farmers use their own Pinctada chemnitzii and make use of hatchery-bred molluscs.

Vietnam

Apart from attempts in the nineteen sixties, even before the Vietnamese War, pearl farming started in 1991in the Bay of Halong in northern Vietnam. Since the late nineteen nineties more than 20 pearl farms were established along the whole coast, as far south as Nha Trang. The farms use Pinctada chemnitzii that is endemic and  produce their spat in hatcheries. They do probably not import molluscs from China but are reputed to export themselves to both China and Japan.  Pteria penguin  is also used for the production of cultured blister pearls (so-called Mabe pearls) and there are limited attempts to produce South Sea cultured pearls with Pinctada maxima.

In 2010, production amounted to 1.5 tons.  It is probably right to suppose that the largest part is sold through Japan. The pearls have a very good nacre thickness of up to 1.2mm and they often have a creamish look.

The American Eliko company is selling a new type of "blue Akoyas from Vietnam." They come in sizes of 6.5-7 to 12-12.5mm. Shapes are distinctly off-round to baroque and colours resemble very much the new colour-induced Japanese Akoyas described above.

"Galatea" pearls

It is interesting to note in this context that Chi Huynh, owner of the Californa-based Galatea company and himself Vietnamese in origin, chose his homeland for growing black pearls with Pinctada margaritifera imported from French Polynesia. Huynh uses precious stones like amthethyst, citrine and turquoise as beads and later carves petal-like patterns into the black pearly layers. Huynh had originally intended to produce pearls in French Polynesia but was at first denied permission by the government as nacre thickness was below 0.8mm, a requirement established in 2001.

Cultured Pearls from the Pacific Ocean

Black South Sea Cultured Pearls

In the Pacific Ocean occurs a variety of Pinctada margaritifera that is commonly known as the black-lip and described as Pinctada margaritifera cumingii. It is so-to-say a subspecies of the common Pinctada margaritifera that occurs worldwide in the Indo-Pacific Ocean. In French Polynesia, the  farm of Jacques and Hubert Rosenthal from Paris, grandsons of the legendary Leonard Rosenthal, delivered the first 71 pearls in 1972. The total production of French Polynesia amounts today to 12.5 tons but had undergone many changes in the government’s policy of supervising farming and marketing. Today, high qualities can still reach high prices but they are only a third of the late eighties. Good qualities can be bought for under one to a few thousand dollars and low qualities in baroque circled shapes can be had for as low as two hundred dollars.

In the early years 2000 a chocolate coloured Tahitian cultured pearl appeared on the market that had been subjected to a type of treatment involving bleaching and heat. No artificial dye is being used  but the treatment has nevertheless to be declared.

Otherwise, artificial colouration is also to be encountered but it is in the realm of imitation and fakes and it is usually used for low qualities.

The Cook Islands

In 1994, the Cook Islands supplied 5 per cent of the world production of black South Sea cultured pearls. They looked similar to pearls from French Polynesia and could only be distinguished by insiders.  The pearl dream was dealt a fatal blow in November 1997 when a typhoon destroyed all farms on Manihiki island. The pearl industry has never really recovered and production was down to 300 kilograms in 2010. The government, represented by the Cook Islands Pearl Authority (CIPA), has recently become active again. A new brand name, Avaiki, was introduced and first advertisement, looking for international distributors, have been placed in leading Asian trade magazines.

The Fiji Islands

From 1966 till 1979,  the Asian Pearl Company operated a pearl farm on Gau Island and produced mainly Mabe pearls with Pteria penguin. While small local enterprises may have continued over the decades, the Fiji Islands only came in the focus of  the international pearl trade when the  J. Hunter Pearls Fiji Pearling Conservancy company established two farms in  2005. They are situated on  Vanua Levu Island, one of the two largest islands. Savusavu farm is in  Savusavu Bay and Kioa farm is in  Buca Bay, at a distance of about 60 kilometers from each other. So far, the farms make use of about 100.000 Pinctada margaritifera molluscs that are endemic in Melanesia. Similar to French Polynesia, new molluscs do not come from hatchery stations but from spat collections, a work being done by local women from nearby villages.

Since 2007, Fiji pearls of fine qualities are offered on the world market through auctions to which only about 20 selected international buyers are invited. 30.000 pearls were offered in the first year, followed by 20.000 pearls in 2008, 15.000 in 2009 and 9.500 in 2010. Pearl sizes go from just under 11mm up to 17mm. Blue and green body colours are observed but also chocolate, orange and yellow.

White South Sea Cultured Pearls

Today’s  South Sea market is characterised by a significant division between the  bulk of commercial qualities, the middle range and the high range with exquisite golden colours or white pearls with a pink overtone. They can fetch the highest prices for cultured pearls. Australia excels in white pearls and high qualities, also due to intensive publicity engagements of its main producers. The Philippines have become famous for their golden pearls, equally due to the activity of the main producer. Indonesia has acquired a reputation  for producing mainly normal to average qualities. This does not exclude fine qualities.

Freshwater cultured Pearls from China

China is the true giant of freshwater pearls and has undergone several stages since the early 1970s when the pearls became known in the west.  The year 1992 marked a distinct change as it saw nearly round pearls that were named "potatoes."

While shapes became ever more round and perfect and colours ever more pink, orange and lilac, leading to high prices, the bulk of the production had irregular shapes and was sold at commercial to cheap prices. All pearls were of the so-called "beadless" type, they were produced by inserting tiny pieces of grafting-tissue into the mussels' mantle.

From  2005 onwards, there were a number of novelties. They were headed by the so-called "Ikecho" pearls, in sizes of up to 20mm, baroque shapes and striking colours.They were produced by using a mother-of-pearl bead as a nucleus that was implanted into the gonad. While the Ikechos are expensive, the similar-looking "Fire balls" that followed  soon, are less expensive. They are produced by inserting round mother-of-pearl beads into already existing pearl sacks in the mantle and are characterised by a type of tail. Often the beads join during pearl growth and produce double to triple fire balls.  When a flat, button-shaped bead is used, coins or buttons are produced. Upon their harvest, the pearl sacks are allowed to shrink and the mussel goes for a last growth period back into the water. The result are flat, petal-shaped pearls that the  Chinese trade has termed Keshis. The name is allowed because in 2009 the CIBJO Pearl Book has extended the definition of Keshi cultured pearls for including pearls from freshwater.

2009 saw another novelty, the so-called "Soufflés." They resemble "Ikechos" but are lighter in weight. The secret is that they are produced by inserting mud from the pond into an existing pearl sack. The mud is later washed out during pearl drilling. The name "Soufflé" is staken from a French equivalent for natural pearls that have a muddy interior.

Elisabeth Strack

Elisabeth Strack

About Elisabeth Strack

Elisabeth Strack started her gemmological training with Professor Schlossmacher at the Institut für Edelsteinforschung in Idar-Oberstein and she continued it in England and at the Gemological Institute of America. In 1967, she was awarded the Tully Medal as a Fellow of the Gemmological Association of Great Britain.

After several years of practical work as a gemologist with mining companies, jewellers and institutions of the jewellery industry in different countries, she established her own gem testing laboratory in Hamburg in 1976, which she named "Gemmologisches Institut Hamburg" in 1994.

Elisabeth Strack has since made a name for herself as an independent expert. Her daily work enables her to see hundreds of pieces of jewellery which she documents and uses as a basis in her scientific work. Elisabeth Strack travels frequently and gives lectures and seminars both in Germany and abroad. She has published three books with Rühle-Diebener-Verlag. The first edition of her pearl book appeared in 1982.

JIBNA