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Pearl Glossary

comprehensive guide to the world of beautiful pearls

A

 

Abalone

A mollusk known as Haliotis gigantea and considered as a delicacy by Japanese. Abalone pearls are found in abalone off the coast of California, Oregon, Alaska, Mexico, Japan, South Africa, Australia, and New Zealand. 

As their pearls are rare, one estimates that the chance of finding a natural pearl of any size or shape in an abalone is one in 50,000. Reasons for rarity are that large pearls require approximately eight to ten years to form. Since animals are fished commercially for meat when they are four or five years old sufficient time has not allowed pearl formation. Also, not all Abalone produce pearls. A specific combination of factors must exist for natural pearl formation: invasion of a foreign object, usually a living parasite, sufficient movement of the animal, correct immune system response, correct water temperature, and availability of correct diet. 

Abalone pearls usually have unique baroque shapes which are sought after by designers, and their colors may be any combination of shade of green, blue, pink, purple, silver, or white, and often in brilliant combinations. Blue and pink colors are usually highly sought. Natural pearl shapes can vary from round or ovalish to flat baroques to giant horn shapes. Several pearls of different colors and shapes can be found in a single animal. Natural Abalone pearls are formed in thick nacreous layers joined together by organic conchiolin. 

Natural Abalone Pearls can be utilized in all types of jewelry and in rare instances pairs can be matched up and over time en suite sets can be painstakingly collected.

 

Adductor

The muscle of bivale mollusc attached to the inner valve. It functions to close the oyster shells (relaxation of the adductor muscle allows the shells to gape open).

 

Akoya

A bivale mollusc used to produce seawater cultured pearls, that are well-known for their superior luster and color. Its scientific name is pinctada fucata. Less than 50 percent of Akoya oysters survive the nucleation process. Of all Akoya pearls produced, less than 5 percent are considered high quality. 

In the 1950s, cultured pearls meant Japanese akoya pearls, when Mikimoto owned the most of the oyster beds. Since 1960s, the production of the cultured pearls began to spread to other pearl farmers in Japan and to other parts of the world.

A pearl produced by this mollusk is classic and has usually white body color, while its overtone can vary from pink, silver, green, to cream, and has a higher possibility of being round more than many other kinds. Combined with its high luster, those features make it especially attractive.

However, the mollusk rarely produces a pearl exceeding 10 mm in size, and when it does, it commands a very high price.

 

Ama

Japanese female divers diving mainly for pearls. Traditionally and even as recently as 1960s, they were trained to dive without scuba gear or air tanks. They are famous for diving for pearls but originally they dived in search of seafood.

 

Andy Muller

The author of "Cultured Pearls The First Hundred Years." This excellent book features the pearl histories around the world with beautiful pictures.

 

Antoinette Matlins

The author of the book "The Pearl Book The Definitive Buying Guide." She precisely describes how to value and identify many different types of pearls.

 

Aragonite

A carbonate mineral to consist of nacre (outer layer of pearl).

 

B

 

Baroque

Pearl shape that is irregular or odd. The most valuable of baroque pearls are the South Sea and Tahitian pearls. They should have distinctive shape which is interesting and attractive, with beautiful color and iridescent flashes.

Although they are more common and therefore less expensive compared to round ones, they can create beautiful jewelry.

 

Biwa pearl

Cultured freshwater pearls in freshwater of Lake Biwa, Japan.

 

Black pearl

A black pearl can be cultivated from either black-lip oyster (Pinctada Margaritiļ½†era), La Paz Pearl oyster (Pinctada mazatlanica), or Rainbow-lipped oyster (Pteria Sterna). Some other pearls can be died black as well. Tahiti is the leading producer of high quality black pearls.

 

Black-lip oyster

Pinctada margaritifera. See P. margaritifera.

 

Blemish

Refers to any surface defect on a pearl. Blemishes may include cracks, chips, dull spots, wrinkles, spots, holes, bumps, and pits.

 

Blister

A pearl made when internal surface of shell is bloated over a foreign object, dome-shaped on one side and flattened on the other.

 

Blister pearl

Easily mistaken with a blister, this pearl has more scarcity value. This is made when a natural pearl moves in the mollesc and is attached on the internal surface of shell. This is also dome-shaped on one side and flattened on the other. See also Mabe pearl.

 

Button pearl

A flat, round button-shaped pearl.

 

C

 

Canilli Pearl

A small Italian company in Japan exclusively dealing with selected pearls. Known for good prices and service.

 

Carat

Unit of weight for cultured pearls often used in Europe. 1 carat (symbol ct) corresponds to 0.20 grams. 1 gram = 5 carats. One momme is equal to 18.75 carats.

 

Carotenoids

Botanical organic pigments. Their presence on pearls result in the coloring of pink pearls, and the color may fade after long time because they can be decomposed by long-time sun exposure.

 

Chemical composition

Pearls are usually consisted of 82-92% calcium carbonate (mostly aragonite), 4-14% conchiolin (organic substance), 2-4% water, and other chemical elements (Mn, Mg, Sr, K, Li, Cu, Zn, Cl, P)(less than 1%).

 

Choker

A necklace 14-16" (35-40cm) long.

 

Circles

Concentric rings on the surface of a pearl. If circles cover over 1/3 of the pearl's surface, it may be referred to as a circle pearl.

 

Clam

Whitish or yellowish pearls, produced by molluscs of the general Pinctada or Unio.

 

Clean

Term used to describe the pearl surface without any spots or blemishes.

 

Collar

A necklace that just fits around the neck, usually 10-13" in length. May consist of two or more strands.

 

Color

Base color of the pearl.

 

Color treatment

Pearls come in natural colors ranging from white or beige to pinks, grays, black and blues. Pearls can also be dyed a specific color, or a dye process may be used to enhance or change the pearls natural color.

 

Coloring by impregnation

An artificial colorant is impregnated into the pearl hole to result in a pinkish tone.

 

Conch pearls (or Great conch)

Pearl produced by a conch, a tropical saltwater mollusc found in the Caribbean. Conch shell interior is often lovely pink color with a very smooth surface. Its pearls are very rare and valuable. Conch pearls occur in pink and orange colors. Pink is the most valuable color. Pink and orange conch pearls often resemble to corals by appearance.

 

Conchiolin

The protein layer that is secreted by a mollusc on the nucleus. It works as the adhesive of aragonite, allowing more layers to build.

 

Concretion

Inorganic, organic, or mixed aggregate; foreign body that forms in an organism by precipitation of salts or by the gradual accumulation of materials.

 

Connective tissue

Tissue that connects with other tissues. In molluscs: intermediate muscular part between the mantle.

 

Corn pearl

A pearl shaped like a kernel of corn.

 

Cultivated pearl

Cultivation is a sophisticated process to grow pearls. Skilled technicians insert irritants (mother-of-pearl seeds or other materials) in the molluscs and the nacre starts to accumulate around it.

 

Cultured pearl

Another term for cultivated pearl. A pearl made intentionally by inserting a bead nucleus or mantle tissue into a mollusk

 

D

 

Dehydration

Pearls can lose moisture content when kept in a very dry condition, or in a long period of time. Without moisture, they reduce their luster.

 

Diffraction

A bending and spreading of rays by encountering an obstruction.

 

Dome

A blister-shaped pearl like mabe, which forms inside of the mollusc shell. More unique shaped than mabe because when it's cut off from the shell, part of the shell is also remained.

 

Dredge

An equipment to harvest many oysters at once by scraping the seabed.

 

Dust pearl

A very tiny pearl weighing a slight fraction of a grain.

 

Dyeing

Opposite of bleaching. Treatment applied on pearls to add colors with various chemical components.

 

E

 

Epithelium

It covers the mantle, protecting the surface that may come into contact with foreign substances. Secretes the material that forms pearl layers.

 

F

 

Freshwater cultured pearl

Cultured pearl that is grown inside a mollusc that lives in fresh water, such as a pond, lake, or river.

 

Freshwater pearl

Any pearl produced by a mollusc living in fresh water.

 

​G

 

G.I.A.

Gemological Institute of America. Established in 1931, it is the world's largest and well-known institute of gemological research, learning, and grading. They are highly expertised in identifying and grading precious and semi-precious stones. They also grade some aspects of pearls.

 

Gold-lip shell

A kind of Pinctada maxima, mainly found in the northern equatorial waters of Southeast Asia. Its inner shell edges are gold or yellow and it usually forms golden-colored or yellowish South Sea pearls.

 

Grades of Japanese akoya pearls

Among professionals and exclusive jewelry stores, Japanese akoya pearls are often graded from AAA , AA, A+, and A (in the order of higher qualities).

 

Grades of South Sea and Tahitian pearls

Among professionals and exclusive jewelry stores, South Sea and Tahitian pearls are often graded from A , B, C, and D (in the order of higher qualities).

 

Grading

A system used for evaluating pearls. Even though there is no established criteria internationally recognized, there are a handful of professional institutes which offer grading service.

 

Graduated

The largest pearl is called the center, whereas the two pearls next to the center are called shoulders.

 

Grafting

Also termed nucleation or implantation. Process of inserting a hard bead nucleus or piece of soft mantle tissue into a mollusc body or mantle of the mollusc. The nucleus or mantle tissue serves as the 'seed' to irritate the mollusc to produce a pearl.

 

Grain

The unit of weight once used for natural pearls. Corresponds to 0.05 grams. 1 gram = 20 grains. Carat weight is now generally used.

 

H

 

Half

A pearl that have been sanded on one side. see also abalolne

 

Half-drilled

A pearl that is half-drilled, often used for rings or earrings,

 

Haliotis

The gastropod known commonly as the abalone. Generates very colorful, lustrous baroque pearls and mother-of-pearl, as well as edible flesh.

 

Hanadama

Japanese term for exceptionally high quality pearls. Often found in loose but very rare in strands.

 

I

 

Iridescence

Exhibition of rainbowlike colors on a pearl surface. It is caused by the overlapping of successive layers, which breaks up light falling on the surface.

 

Irritant

A minute snail, worm, fish, crab or other small particle can be an irritant for a natural pearl. For a cultivated freshwater pearl, usually a piece of mantle (membranous part that secretes nacre and covers the inner shell surface) is used. For cultivated saltwater pearls, a shell bead (often from the Mississippi River) is most commonly used as an irritant.

 

J

 

J.P.E.A.

Japan Pearl Export Association. It has been operating Cultured Pearl Quality Inspection and Tag system since January 1999. This new system has replaced the governmental service of pearl inspection in 1998 as a part of the national administrative reforms.

 

K

 

Kan

Japanese unit used for pearls equals to 1,000 momme.

 

Keshii pearl

It is a non-nucleated pearl, accidentally created when an oyster rejects an implanted nuclear but a particle left from the bead can lead to formation of nacre.

 

Knotting

Knots in between pearls are to help protect the pearls from scratching each other, which can result in marring and chipping. It also helps secure the pearls and minimizes the chance of losing some of the pieces in case the necklace or bracelet breaks.

L

 

Luster

Pearl's ability to reflect light. One factor to evaluate pearls based on their radiance. The higher the luster, the more valuable the pearls. High luster gives almost mirror-like reflections.

 

M

 

Mabe

A dome-shaped pearl with a flat back that grows on the internal wall of a mollusc's shell. In some cases, a plastic dome-shaped nucleus is attached on the internal surface of a mollusc shell. When the nucleus is sufficiently covered with nacre, the pearl is detached from the shell. The nucleus is removed and the cavity is filled with an epoxy resin and backed by a mother-of-pearl plate. Mabe pearls are sometimes called blister pearls.

 

Mallorca (or Majorca)

An imitation pearl from Spain.

 

Mantle

The thin tissue membrane that attaches a mussel to the inside of its shell.

 

Matching

The process of matching similar pearls by luster, surface, shape, color, and size for a necklace or other piece of pearl jewelry.

 

Matinee

A necklace 20-26" (50-66cm) long

 

Mikimoto

Kokichi Mikimoto was one of the initiators of pearl cultivation. After 85 years Mikimoto Pearls founded by him remains the leading company in the world market.

 

Mollusk

An aquatic, soft-bodied invertebrate that lives in a shell. Mollusks are found in seawater and freshwater.

 

Momme

A Japanese weight measurement used for pearls. One momme equals 3.75 grams or 18.75 carats.

 

Mother of pearl

The smooth, hard pearly lining on the interior of a mollusk shell. Also called nacre.

 

Mussel

A generic name for certain types of freshwater or seawater bivalve molluscs.

 

N

 

Nacre

Also known as mother of pearl, it is naturally formed by layers of calcium carbonate platelets, in the form of aragonite and conchiolin, separated by elastic biopolymers. This mixture of hard and elastic domains makes the material strong yet resilient.

Nacre is secreted by the mantle tissue of certain mollusks. In these mollusks, nacre is continually deposited onto the inner surface of the animal's shell (the iridescent nacreous layer, commonly known as mother of pearl), both as a means to smooth the shell itself and as a defense against parasitic organisms and damaging detritus.

 When a mollusk is invaded by a parasite or is irritated by a foreign object that the animal cannot eject, a process known as encystation entombs the offending entity in successive, concentric layers of nacre. This process eventually forms what we call pearls and continues for as long as the mollusk lives.

Pearls with thicker nacre are highly valued.

 

Natural pearl

Pearl grown naturally without human intervention. Unfortunately, seawater natural pearls are rarely available now. Main reasons are water pollution and excessive fishing. Usually they have irregular shapes like a pear or drop. Sweetwater natural pearls used to be often found in Asia, Europe, and North America. Particularly ones from Mississippi river were well appreciated.

 

Nishikawa, Tokichi

Tokichi Nishikawa, Japanese government biologist, and his son-in-law succeeded in perfecting technique of round pearl cultivation in 1907.

 

Nucleation

The process of nucleating a mollusk for cultivating a pearl. Also called as grafting or implantation, nucleation involves the human insertion of either a hard bead nucleus or soft mantle tissue into either the body or the mantle tissue of a mollusk. The hard bead nucleus or soft mantle tissue serves as a "seed" or "irritant" to produce a cultured pearl.

 

Nucleus

Typically, a small rounded piece of shell from an American freshwater mussel. It is recognized in the mantle tissue as a foreign obstacle and the nacre is formed around it. For freshwater pearl cultivation, the nucleus usually is a shaped piece of mantle from another freshwater mussel.

 

Nugget

A pearl with an irregular surface

 

O

 

Opera

A necklace twice size of a choker-28-32" (70-90cm) long.

 

Orient

The distinctive iridescent colors seen on the surface of a pearl.

 

Oriental pearl

Natural pearls found in the Persian Gulf, Red Sea, or Gulf of Myanmar. Also, can be referred to a pearl occurring naturally in saltwater.

 

Overtone

Overtone refers to the presence of secondary colors to a pearl body color.

 

Oyster

The name oyster is used for a number of different mollusks. Inside a usually highly calcified shell is a soft body. Strong adductor muscles are used to hold the shell closed.

 

P

 

P. fucata

Also known as P. martensii, the oyster used to produce cultured Japanese and Chinese pearls.

 

P. margaritifera

Pearl-producing oyster with black, white, or golden colored "lips," producing nacre similar in color to its "lips." The black-lip variety is used in Tahiti and other parts of French Polynesia to produce natural black cultured pearls.

 

P. martensii

See P.fucata.

 

P. maxima

A large oyster used to produce South Sea cultured pearls; includes the "silver-lip" which produces the silvery white varieties typical of Australia, and the "yellow-lip" which can produce yellow and golden pearls.

 

Peacock pearl

A pearl of the distinctive green color unique to Tahitian black pearls. The most valuable color among Tahitian pearls.

 

Pearl

A pearl is a hard, rounded object produced by certain mollusks. Pearl is valued as a gemstone and is cultivated or harvested for jewellery.

Pearls are formed inside the shell of certain mollusks. As a response to an irritating object inside its shell, the mollusk will deposit layers of calcium carbonate in the form of the minerals aragonite or calcite (both crystalline forms of calcium carbonate) held together by an organic horn-like compound called conchiolin. This combination of calcium carbonate and conchiolin is called nacre, or as most know it, mother-of-pearl.

The unique luster of pearls depends upon the reflection and refraction of light from the translucent layers and is finer in proportion as the layers become thinner and more numerous. The iridescence that some pearls display is caused by the overlapping of successive layers, which breaks up light falling on the surface. Pearls are usually white, sometimes with a creamy or pinkish tinge, but may be tinted with yellow, green, blue, brown, purple, or black. Black pearls, especially Tahitian, are highly valued because of their rarity; the culturing process for them dictates a smaller volume output due to rejection by the oysters. 

The value of the pearls in jewelry is determined by a combination of the luster, color, size, lack of surface flaw and symmetry.

 

Pearl doctor

An artisan who peels layers of nacre from blemished pearls in order to uncover a more perfect surface.

 

Pearl farm

An operation where oysters are bred and grown in captivity for the production of cultured pearls, and then nucleated and tended until cultured pearls are ready to be harvested.

 

Pearl fisheries

A site where mollusks are harvested in the wild for the purpose of finding pearls or mother-of-pearl.

 

Pearl Institute

An institute located in Tokyo which is well-known in Japan for extensively offering pearl grading service.

 

Pearl oyster

All oysters (and, indeed, many other bivalves) can secrete pearls, but those from edible oysters have no market value. The Pearl Oysters come from a different family, the Pteriidae (Winged Oysters). Both cultivated pearls and natural pearls are obtained from these oysters, though some other mollusks, for example freshwater mussels, also yield pearls of commercial value. The largest pearl-bearing oyster types is the Pinctada maxima, which is roughly the size of a dinner plate. Not all oysters produce pearls. In fact, in a haul of three tonnes of oysters, only around three or four oysters produce perfect pearls.

These oysters, and other mollusks, produce pearls by covering an invading piece of grit with nacre (or as most know it, mother-of-pearl). Over the years, the grit is covered with enough nacre to form what we know as a pearl. There are many different types and colors and shapes of pearl, but this depends on the pigment of the nacre and the shape of the piece of grit being covered over.

The pearls for jewelry are usually cultivated, placing a single piece of grit, usually a piece of polished mussel shell, inside the oyster. It takes three to six years for an oyster to produce a beautiful pearl. Even though if more valuable, natural pearls are very rare nowadays.

 

Pearl sac

A cyst of epithelium (mantle) tissue that surrounds an irritant inside a mollusk's shell and secretes nacre around it to form a pearl.

 

Pearlescent

Resembling pearl or mother-of-pearl in iridescence and luster.

 

Pinctada

The genus of oysters that produce quality pearls. The best known are those which produce Akoya pearls, namely, the Pinctada fucata martensi, the pinctada vulgaris, and the Pinctada radiata (pinctada imbricata), and those which produce South Sea pearls, the Pinctada maxima and the Pinctada margaritifera.

 

Pink pearl

Refers to Conch pearl.

 

Pinna nobilis

A Mediterranean bivalve that makes lustrous pearls that deteriorate rapidly because of their unusual crystalline structure and high water content. Also sought for its edible flesh. It produces pearls (natural, called Pinna pearls) with a particular aspect and crystal structure, colored pink or reddish, orange, yellowish or brown to black with little iridescence. It does not have much luster and has a roundish or elongated, drop or pear shape.

 

Placuna placenta

Bivalve mollusc whose shell measures around 15 cm. It is famous for its transparency, especially during the first years of growth and is called window-pane shell or Chinese glass. It produces small, irregular, opaque lead-colored pearls.

 

Pleurobema cordatum

Freshwater mollusc that lives in the Mississippi river and its tributaries. It is known as pig-toe. The mother-of-pearl has a typical pinkish white coloring and is used to make the rigid nuclei of saltwater cultured pearls.

 

Potato pearl

Refers to a pearl with an oblong shape, such that it resembles a potato. Most potato pearls are freshwater cultured pearls from China.

 

Princess

A necklace 16-20" (40-50cm)long.

 

Pteria (Magnavicula) sterna

Rare "rainbow-lip" oyster unique to the Gulf of California. Produces vivid iridescent purplish nacre and a colorful array of natural pearls; now used in Mexican pearl culturing.

 

Pteria penguin

Mollusc used to produce mabe pearls. Also called "penguin shell," "mabe shell," the "wing shell," the "black wing shell," or the "gold wing shell." It can grow as large as 25cm, and its inner shell has a beautiful, rainbow-colored iridescence that ranges from light pink to dark pink to slightly bluish shades, often with a strong metallic luster.

 

Q

 

Quadrula

Freshwater bivalve pearl mollusc.

 

R

 

Radiograph

Special photographic film with emulsion more sensitive to short wavelength radiation. Used in radiographic analysis, based on how permeable the materials constituting pearls are to X ray

 

Recoating

A kind of treatment applied to pearls. A rough surface of a pearl can be made smoother and more shiny by covering it with polydimethylsiloxan, a type of silicone.

 

Renee Newman

A gemologist and the author of the famous book: "Pearl Buying Guide: How to Evaluate, Identify, and Select Pearls & Pearl Jewelry." It provides many distinctive photos and clear explanations.

 

Rhodoid

A pearlized laminate used for tabletops and other objects. Also know as Frenceh Deco Linoleum.

 

Rice pearl

A freshwater cultured pearl with a crinkled surface and elongated shape, resembling a grain of rice. Most rice pearls originate from China or the US.

 

Roman pearl

Imitation pearl. Alabaster bead covered with an iridescent substance (isinglass, shiny oyster flakes, mother-of-pearl powder).

 

Rope

A necklace longer than opera-40"+ or 1 meter or longer.

 

S

 

Saltwater pearl

Any pearl, natural or cultivated, that is grown in a mollusc that lives in salt (ocean) water.

 

Seawater natural pearl

Look at natural pearl

 

Seed pearls

Tiny naturals weighing under 1/4 grain, usually less than 2 millimeters in diameter.

 

Semi-cultured

Imitation

 

Shape

A quality evaluation category used to describe the shape of a pearl. The most valuable pearls are round. Other shapes of pearls include off-round, drop, oval, button (one flat side), circled, semi-baroque and baroque (asymmetrical/free form).

 

Shell carving

The practice of carving mother-of-pearl and other types of shell into figuines, trinkets, and objects d'art.

 

Shinju

Japanese term for pearl

 

Size

A quality/price evaluation category used to describe the size of a cultured pearl. Size descriptions are expressed in millimeter and measured by the diameter of a pearl.

 

Sorting

The process of sorting pearls before matching and jewelry assembly to separate pearls by luster, surface, shape, color and size.

 

Soufflure

A hollow pearl, formed when an organic irritant decomposes inside its pearly coating before the nacre hardens. Gases released by the rotting object inflate the nacreous buildup like a bubble.

 

South Sea cultured pearl

Pearls cultured in the white-lip oyster (Pinctada maxima) mainly in Australia, Indonesia, Philippines, and Burma. South Sea cultured pearls generally range in size from 8 mm to 18 mm or more in rare cases and can range in color from white to gold, with silver, cream, and champagne in between.

 

Spat

An oyster larva before it forms its shell.

 

Stombus Giga

A large, horny univalve of the Caribbean, which has a smooth, pink interior. Produces porcelaneous, pearl-like gems and edible flesh. Commonly known as conch or great conch.

 

Stringing

A process to put pearls together to form a strand.

 

Surface

A quality evaluation category used to describe the amount of blemishes on the surface of a pearl or cultured pearl. Surface descriptions range from clean (no visible blemishes) to heavily blemished.

 

Surface magnification

A method of identifying authenticity of pearls by examining the pearl surface with a 10-power magnifier such as a loupe. If it looks grainy, there is a good chance it is an imitation. 

A surface with tiny, crooked lines giving it a scaly, maze-like appearance is the characteristic of cultured and natural pearls.

 

Sweet water natural pearl

Look at natural pearl

 

Symmetrical

A symmetrical round pearl may reach the highest value. However even if not round, in some cases, a symmetrical oval or teardrop pearl can be highly valued as well.

 

T

 

Tahitian cultured pearls

Cultured pearls produced by the black-lip oyster (Pinctada Margaritifera) found in the atolls and lagoons of French Polynesia. Tahitian cultured pearls are natural in color and are produced in hues of silver, gray, green, orange, gold, blue, purple and black.

 

Tasaki Pearl

A well-known Japanese company that produces and distributes pearls. Has a strong share in Japan.

 

Three Quarter

A pearl usually sanded one side because of a defect.

 

Tissue-nucleated pearl

A pearl cultivated using just mantle tissue

 

Tooth test

A method of identifying authenticity of pearls by rubbing them lightly along the biting edge of your upper front teeth. If they feel gritty or sandy, it's likely they are cultured or natural pearls. If they feel smooth, they are probably imitations. However, unless done properly, it may hurt the pearls. Not only there are some imitation pearls that feel gritty, some real pearls may feel smooth, especially when they are polished. So if you would like to use this test, it would be wise to combine with another test such as a magnification test.

 

Treatment

Artificial modification of the chemical and/or physical properties of a gemological material. In pearls, any operation for changing and improving their aspect. The most common treatments are: coloring by impregnation, bleaching, exfoliation, impregnation with oil, infiltration, irradiation, recoating, and dyeing.

 

Tridacna

Marine bivalve pearl mollusc of the family Tridacnidae. It has an exceptional shell that can reach 1.5 meters in length and weigh over 200 kg. It was once used to hold holy water in churches. It can produce irregular, opaque, white pearls, without iridescence, also called Conch.

 

Tritigonia

Freshwater bivalve pearl mollusc.

 

Turbo petolatus

Marine bivalve pearl mollusc of the family Turbinidae. It lives in the waters of Polynesia. It produces rare greenish-yellow pearls.

 

Turkish rose pearl

Imitation pearl. Bead cut from a homogeneous paste of rose petals (ground, dried, bathed several times in rose water and compacted). Polished with rose oil, it has a subtle, delicate scent.

 

U

 

Umbo

Central swelling surrounded by the concentric lines decorating the shells of bivalves. It is also called apex.

 

Uniform (strand)

Made up of pearls of equal size.

 

Unio

A genus of freshwater mussel that makes small, irregular pearls with good luster.

 

Unionides

General term for mussels, derived from the genus name Unio.

 

Univalve

A mollusk with a one-part shell, such as a snail.

 

V

 

Valve

The shell of a mollusk. Univalves have one valve, bivalves have two.

 

W

 

White pearl

A pearl with basically white body color. Can range in tint from white, cream, yellow, and golden to pink, green, blue, and silver.

 

White-lip oyster

A large species of oyster from the Pinctada maxima family, found in the waters off Australia, Indonesia, the Philippines, and Japan. These oysters grow in excess of 12 inches in length and can produce a wide range of South Sea cultured pearls in sizes from 8 mm to over 22 mm and in colors including silver/white, pink, and cream.

 

Comprehensive pearl glossary. Find the words and terminologies about pearls in this extensive pearl glossary from A to Z. Terms in this pearl glossary are updated twice a year. We also welcome customers suggestion for addition and correction of terms. 

Information on this pearl glossary is as of September 1, 2007.