Larimar & Tahiti pearl by Blue Stone

The jewel collection by Blue Stone
The alliance of sea and stone, of mineral and animal…




Over three thousand years ago, the Chinese already used molds to cover diverse objects with a mother-of-pearl coating (Lac Tahu, Kiangsu) :
And starting from the 12th century, mother-of-pearls buddhas were also discovered, resulting from the coating of a lead or tin model slipped between the shell and the coat of soft water mussels. The shell was open on each side with bamboo rods. The mussels were then dropped back into the lake.
Between 1560 and the beginning of the 20th century, most of the pearls on European crowns or religious treasures were provided from the Gulf of California. The two main pearl shells were the Pinctada Mazatlancia and the Pteria Sterna. The Pinctada Mazatlancia oyster provides baroque and semi-baroque dark grey pearls, which can more rarely be blue, green or purple, and as large as 20mm long.

From the end of the 19th century, fishing techniques became more sophisticated with new sophisticated methods such as the « diving suit ». The latter enables the shells to be collected at over 80 meters deep. Most of the collected pearls were then sold in Paris.

Around 1880, the Americans tried oyster culture for the first time. Tokichi Nishikawa (1874-1909) was the first person in Japan to produce round cultural pearls, and his method was borrowed, developed and exploited later by Mikimoto. Their success was due to the better adaptation of their shell (Pinctada Martensii) to its cultural environment. Cultural pearls from Japan were only set on the market in 1920.

In Kobe’s surroundings, on the shores of the island now known as the « Pearl Island », Mikimoto developed some breeding techniques, such as baskets tied on hanging ropes, and used a method involving the introduction of a coat transplant to create layers of pearl around the mother-of-pearl core.
A friend of Mikimoto, the dentist Otikichi Kuwabara, guaranteed the implementation. Mikimoto brilliantly organized his pearl breedings and persevered, despite the oysters’ elevated death rate (caused by typhoons, red muds..).
At the end of his life, he was the sovereign of a pearl empire that survived the Second World War. The secrets of his cultural techniques were well kept, and pearl breedings could only survive outside Japan in the presence of a Japanese transplant physician.


The Pinctada margaritifera, or black lip pearl oyster was used during the 18th century by the polynesian people as a fishing tool (the hook), a decoration object but also trade money. The arrival of navigators in the 19th century, developed a new form of trade of the mother-of-pearl and greatly expanded exportations. The mother-of-pearl trade was destined to marquetry, buttons…
The one-year average sales of mother-of-pearl products between 1830 and 1890 reached 900 tons, 800 between 1890 and 1930 and 700 until the 1960’s. The natural oyster livestock living in the lagoons of polynesian atolls were considerably reduced during this period. At the beginning of the 20th century, the local authorities instated fishing quotas, closing the exploitation of certain atolls.


In 1940, Mr Simon Grand, oyster aquaculturist from Arcachon (France), organized the first experiments of collecting and breeding of the Pinctada margaritifera in the islands of Tuamotu and Gambier.
After this, the main goal of biologist’s missions was to handle the exploitation of the natural stock of mother-of-pearl.
In 1963, the coming of transplant physicians who operate in Hikueru and Bora-Bora on transferred mother-of-pearls was organized, with the participation of an Australian pearl company. The harvest observed two years later was of excellent quality, and aroused an important interest for pearl culture. In 1967, a biologist named Mr Reed, studied the feasibility of a pearl farm in Manihi and Tuamotu.


The naturalist Linné (1707-1778) shed light on the pearls’ development methods : A microscopic worm, from the cestode family and a mollusk parasite, wriggles between the shell and the coat. Excited by the toxines, it creates its own bubble with a secretion of limestone, isolating itself from the mollusk.
The more the secretion is important, the more the bubble’s tissue is excited, thus creating further secretion. In this way the pearl keeps growing, if not ejected by the mollusk in a brisk movement.
Pearls are therefore formed by concentric layers of thin aragonite crystal which are disposed in a parallel manner, in a network of chitinous organic matter, called conchiolin.


The fishing technique named « the dive » consists of collecting the oysters by successive divings in apnea.
This method however involves many risks, such as decompression accidents (deafness, serious mental issues, sometimes leading to dementia). What’s more, it is devastating for the livestock, and haphazard on the number of collected pearls.


The breeding process of the pearl oyster is long and demands a huge amount of care, because of the
frailness of the species. The black lips pearl oyster rejects sexual semens which are directly fecundated in the water, at specific periods of the year. After drifting for a month, the young oysters cling on to corals, or die buried in the sand.

The capture: The pearl farmer captures the young oysters in the lagoon on artificial collectors, then raises them in underwater breeding lines for over three years. They will receive attentive care and thorough regular cleaning.

Nacres en chapelet sur les lignes (age + de 36 mois)
Mother of pearls on the breeding lines (aged 36 months +)

Spat removal and breeding: When the collectors are eighteen months old, the mother-of-pearls are separated and pierced (one by one, in the hinge area).
According to their size, they will be bred differently :
– The smaller ones will be put on stranded wires (20mm diameter, 150mm long), on which the motherof-pearls slided on a nylon thread of 200cm long will be wrapped around.
-The others will be disposed in rows on 6mm diameter and 450cm long ropes. Sur les nœuds disposés tous les 20 cm une nacre est attachée avec un fil nylon de 30 cmOn the knots situated every 20cm, a mother-of-pearl is attached with 30cm nylon string.
The grafted oysters are then put back into their natural habit. In the 50 to 60 days following the operation, the grafted tissue will create the pearl bubble isolating the nucleus of the oyster’s organs and begin the long cycle of the pearl’s creation. mother-of-pearl can only stand one transplant and two secondary transplants during its life. 30% of the mollusks die after the operation, 30% of the transplants will only partially cover the mother-of-pearl nucleus, a third only of the oysters will produce tradable cultural pearls.
The thickness of the pearl, which also depends on the grafted oyster’s strength, reaches 0,8 to 2mm.
Over 200 layers of mother-of-pearl are disposed on top of each other all around the nucleus, whose composition is identical to the shell’s. This is what gives the Tahiti pearl its beauty, diversification and impressive diameter.

The harvest: After 24 to 36 months of watching, the pearl farmer will witness the birth of the Tahiti pearl.
It is important to identify the transplant physician’s number and the breeding line’s number to assure a thorough follow-up.


Tahiti pearls are rarely black.
The word does not come from their color but of the oyster species that produces them : the black lips pearl oyster « Pictada Margaritifera, Cumingui variety ».

In 1975, the GIA (Gemmonolical Institute of America) recognized the authentic character of the Tahiti cultural pearl.
In 1983, the official name for the gem became « The Tahiti Cultural Pearl », designated by the CIBJO (Confédération Internationale de la Bijouterie, de la Joaillerie et de l’Orfèvrerie : International Confederation of Jewelry and Silverware).

Classification of the Cultural Pearls of Tahiti
according to the rules defined by the government of French Polynesia in Chapter II of deliberation n°2001-088 of the 12th of July 2001
Very deep Very high Tiny
Deep High A few
Medium Medium Several and light
Feeble Feeble Several and deep

Class A quality  : pearl of superior quality which presents few inclusions visible to the naked eye and located on less than 10% of its surface. They have a very bright shine.
Class B quality : pearl which presents a few inclusions on no more than 30% of its surface, with a correct or medium shine.
Class C quality : pearl which presents several inclusions on no more than 60% of its surface, with a medium shine
Class D quality : pearl of feeble shine with inclusions on more than 60% of its surface.

Density of cultural pearls: The mass of a pearl is evaluated in grains (one grain = 0,05 grams) : a pearl of 20 grains has a diameter of 9mm ; a pearl of 8 has the same diameter as a 1 carat round diamond (6,5mm).

The diameter: The pearl is classified according to its diameter which is established in millimeters. The diameter of a Tahiti cultural pearl generally varies between 8 and 14 millimeters. Some pearls can measure up to 16 or 18 millimeters, which remains exceptionally rare. Today, the largest documented Tahiti cultural pearl has a diameter of 21 millimeters.

Shapes: According to where they grew in the mollusk, pearls can present diverse shapes. In percentage, the round pearls are the less numerous. They have the names that we wish to give them : Olive, Drop, Pear……

Biwa: « Poppy seed » in Japanese. At the beginning, it was the name given to the pearl’s semen. It is associated to the fine pearl by the absence of the nucleus.

The glow: As all organic matters, pearls glow under a black light ; brightly for white pearls, which have whitish shades ; meekly for Tahiti pearls which have reddish/brownish shades (of course, tainted pearls do not glow).

Orient, shine and color of cultural pearls: The pearl’s color resembles the shade of the secreting mollusk’s mother-of-pearl. The color of a pearl is a result of its presence in the seawater and the traces of concentrated chromogenic elements in the secreting mollusk, depending on its species and nutrition.

Conclusion: A product considered a luxury, the pearl can only make you dream. A few countries try to develop this « magical » production.
Since the 80’s, the pearl culture has encountered an important expansion.
The exportation of rough pearls (first exportation market in Polynesia) went from 86 kilos in 1980 to about 10 tons in 2003, for a value of 85 million euros.
This activity, essential on a socio-economic scale, generates about 5000 jobs in over 800 production farms spread over 30 isles and atolls.

Record: A three-rowed Tahiti cultural pearl necklace sold $880.000 at Christie’s in New York, October 1989. A total of 119 pearls between 12 and 15mm with interleaves and a diamond clasp

certificat blue stone

© CopyRight text & pictures: MH nov.2003