# Tahitian pearl - Page: https://taslar.bumba.tr/en/stones/tahitian-pearl/ - Turkish: Tahiti incisi - Also known as: Black pearl, Tahitian black pearl - Kind: Variety - Classification: Organic gems - Crystal system: Orthorhombic - Hardness (Mohs): 2.5–3 - Specific gravity: 2.72–2.78 g/cm³ - Refractive index: 1.53–1.69 - Lustre: Pearly - Transparency: Opaque - Colours: charcoal grey, black, silver, dark green, brownish black, golden, white - Streak: White - Cleavage: None - Fracture: Uneven - Composition: Platelets of calcium carbonate (CaCO₃, mostly aragonite) bound together by an organic substance called conchiolin; this layered material is nacre. Most saltwater cultured pearls have a shell bead nucleus at their centre. - Texture: Thin layers of nacre stacked concentrically, like the layers of an onion. Under a loupe the surface shows fine, wavy lines, which is why it feels slightly gritty against the teeth. - Value ladder: 7/9 step, Precious stone A large cultured pearl grown in the black-lipped oyster in the lagoons of French Polynesia, with green, purple and pink overtones on a grey-black body. A Tahitian pearl is a cultured pearl grown in the black-lipped pearl oyster (Pinctada margaritifera). Although named after Tahiti, most of the farms lie in the lagoons of the Tuamotu and Gambier archipelagos of French Polynesia. It is popularly called a “black pearl”, yet most are not jet black but charcoal grey, silver or dark green, with purple, pink and blue overtones. Usually 8–18 mm across, they are much larger than Akoya pearls. First cultured in the 1960s, they soon became French Polynesia’s most important export. ## How does it form? A Tahitian pearl is a cultured pearl: people start the process and the oyster makes the pearl. The black-lipped pearl oyster is a large species that can live up to 30 years, weigh up to 5 kilograms and grow 30 centimetres across. Young oysters collected in the lagoon are strung on lines and raised; an oyster must be at least two years old and 11–12 cm across before it can be grafted. Into its reproductive organ the technician places a 5–9 mm bead, traditionally carved from the shell of freshwater mussels from the Mississippi basin in the United States, together with a small piece of mantle from another black-lipped oyster. The mantle piece also determines the colour of the pearl. The grafted oysters are tended in the lagoon for at least a year and a half to two years, during which they coat the bead with nacre, layer after layer. Not everything goes to plan: according to 2006 figures, out of every 100 grafted oysters about 20 reject the bead and 25 to 30 die. The colour comes from organic pigments called porphyrins in the shell and from organic matter within the nacre. ## What is it used for? - **Jewellery:** used in necklaces, earrings and rings; its large size and naturally dark colour set it apart from other cultured pearls. In most harvests more than 40 percent of the pearls come out baroque or semi-baroque (irregular in shape), and these are used in jewellery too. - **Mother-of-pearl:** for centuries the oyster was fished for its shell; in the 19th century European sailors traded for the shells, which were used for buttons, inlay and jewellery. - **Economy:** in 2004 pearls made up 71 percent of French Polynesia’s local exports by value and supported about 5,000 people. ## A short history Polynesians treasured the shell of the black-lipped oyster long before Europeans arrived. When the oysters were overfished for mother-of-pearl in the 19th century, the French authorities introduced diving seasons; in 1885 Bouchon-Brandely, one of the biologists they hired, also proposed collecting young oysters and raising them in protected areas, still the main way of obtaining oysters today. In the early 1960s the veterinarian Jean-Marie Domard tried culturing pearls in this oyster with Japanese specialists, and within a few years the first fine cultured pearls were harvested. The first commercial farm opened on Manihi Atoll in 1966. When leasing sea areas became easier in the early 1990s, the number of farms and the output grew fast; as quality fell, the government brought in a minimum nacre thickness, “top gem” and A to D quality grades and export inspections in the early 2000s, and banned the sale of reject pearls. According to a 2006 report, French Polynesia supplied about 90 percent of world production of these pearls, the rest coming from places such as the Cook Islands, the Marshall Islands and Okinawa in Japan. ## How to recognise it - Size is a clue: Tahitian pearls are usually 8–18 mm across, mostly 9–12 mm, and few are smaller than 9 mm. Very black, round pearls of 8 mm or less are generally dyed or irradiated Akoya pearls. - The colour is not flat: as the pearl is turned, green, blue, purple and pink overtones play over a grey, black or brown body. The most characteristic colour is a greenish black known as “peacock”. - A strand in which every pearl is exactly the same colour, or dye concentrated around the drill hole under a loupe, points to dyeing. - Parallel grooves running all the way round the pearl (“ringed” or “circled” pearls) are common in Tahitian pearls. ## Fakes and imitations - Dyed pearls: since the early 1900s small, light-coloured Akoya pearls have been dyed black with silver nitrate solutions, and light-coloured Tahitian and South Sea pearls have also been found darkened. Under long-wave ultraviolet light natural-colour Tahitian pearls glow a dull reddish brown, while dyed pearls usually show no glow or a dull green one; a laboratory makes the final call. - Irradiated pearls: in Akoya pearls darkened with gamma rays, the nucleus made of freshwater mussel shell turns dark, and a dark core can be seen through the drill hole. - Glass and plastic imitations: beads with a black coating; they feel smooth when rubbed against the teeth or against each other. ## What determines its value? Colour, lustre, shape, size and surface quality matter most. The greenish-black “peacock” colour and aubergine (purple) overtones are the most sought after; silver and golden tones are worth less because other South Sea oysters produce them too. Perfectly round pearls are scarce: in a first harvest only about 5 percent are round. In 2002 French Polynesia set a minimum nacre thickness of 0.8 mm for exported pearls; treatments such as dyeing should be disclosed. This information is educational, not buying, selling or investment advice. Value varies enormously with quality and treatment. ## Myths and misconceptions - Myth: Tahitian pearls are jet black. Fact: Though called “black pearls”, most Tahitian pearls are actually charcoal grey, silver or dark green; they span a wide range from white to black, with green, pink, blue and purple overtones. - Myth: Tahitian pearls are grown around the island of Tahiti. Fact: “Tahitian” is a trade name. Most farms lie in the lagoons of the Tuamotu and Gambier archipelagos, hundreds of kilometres from Tahiti, and pearls from the same oyster are also grown on other Pacific islands such as the Cook Islands. ## What is it believed to be good for? This section reports beliefs; it is not health information. There is no scientific evidence for these claims and no stone replaces medical treatment. - According to Tahitian legends, black pearls were emanations from the gods; the important god Oro was believed to have come down to earth on his rainbow, which was thought to be the source of the iridescence of the pearl and its shell. What science says: The colours and iridescence of a Tahitian pearl come not from a rainbow but from light being refracted and reflected by the very thin layers of aragonite and conchiolin that make up nacre, and from organic pigments called porphyrins in the oyster’s shell. ## Did you know? - According to George F. Kunz and Charles H. Stevenson’s book on pearls, published in 1908, Queen Pomare of Tahiti played marbles with black pearls in the early 1800s. - The nacre of a Tahitian pearl can reach 2–2.5 mm in two years; an Akoya pearl lays down about 1 mm in the same time. - In 1989 the largest round cultured black pearl on record measured 20.8 mm across. - In French Polynesia, pearls for export are inspected by the government pearl service and shipped in sealed bags; an X-ray machine was installed at Tahiti-Faa’a airport to stop smuggled exports. ## Where is it found? - Manihi Atoll, Tuamotu, French Polynesia (Historic source): French Polynesia’s first black pearl farm was founded here in 1966 by Hubert and Jacques Rosenthal and was in full operation by 1968; the atoll is still home to many pearl farms. - Ahe Atoll, Tuamotu, French Polynesia (Known locality): Several pearl farms lie in its 138 km² lagoon. - Arutua Atoll, Tuamotu, French Polynesia (Known locality): One of the atolls where the government began restricting pearl-farming permits after 1997, as lagoons became overcrowded. - Gambier Islands (Mangareva), French Polynesia (Major deposit): Its relatively cool waters favour quality pearls; the islands have 129 pearl farms run by fourteen companies. - Manihiki Atoll, Cook Islands (Major deposit): The atoll’s economy is dominated by black pearl farming, with pearl farms dotted around the lagoon. - Okinawa, Japan (Known locality): One of the small producers outside French Polynesia; the black-lipped pearl oyster also lives in Okinawan waters. ## Sources - [Polynesian Black Pearls (M. Goebel & D. M. Dirlam), Gems & Gemology 25(3)](https://www.gia.edu/dam/migrated-assets/_assets/ba822c74c2bdbdc1-Polynesian-Black-Pearls.pdf), GIA, 1989 - [La perle de Tahiti (note de l'Institut d'émission)](https://www.ieom.fr/IMG/pdf/la_perle_de_tahiti.pdf), Institut d'émission d'outre-mer (IEOM), 2006 - [Pearl Description (Gem Encyclopedia)](https://www.gia.edu/pearl-description), Gemological Institute of America (GIA) - [Pearl Quality Factors](https://www.gia.edu/pearl-quality-factor), Gemological Institute of America (GIA) - [Tahitian pearl](https://en.wikipedia.org/wiki/Tahitian_pearl), Wikipedia - [Pearl](https://en.wikipedia.org/wiki/Pearl), Wikipedia - [Baroque pearl](https://en.wikipedia.org/wiki/Baroque_pearl), Wikipedia - [Manihi](https://en.wikipedia.org/wiki/Manihi), Wikipedia - [Ahe](https://en.wikipedia.org/wiki/Ahe), Wikipedia - [Arutua](https://en.wikipedia.org/wiki/Arutua), Wikipedia - [Gambier Islands](https://en.wikipedia.org/wiki/Gambier_Islands), Wikipedia - [Manihiki](https://en.wikipedia.org/wiki/Manihiki), Wikipedia Source: https://taslar.bumba.tr/en/stones/tahitian-pearl/ · Licence: CC BY-SA 4.0