Special Thanks to The Cultured Pearl Information Center for use this Glossary
Abalone pearl: A natural pearl that comes from an abalone, a univalve mollusk known for its tasty meat and iridescent bluish inner shell color. Most abalone pearls are natural, however blister pearls, mabe pearls, and some semi-round pearls are being cultured in these mollusks.
Akoya cultured pearl: The industry term for cultured pearls produced in several species of saltwater oysters to include Pinctada fucata and Pinctada martensi. Akoya oysters are typically found in the cooler waters of Japan and China. Akoya pearls generally range in size from 2 mm to 10 mm and range in color from white, rose, cream, gold and blue/gray. High quality Akoya cultured pearls are renowned for their bright and intense lustre.
Baroque: An industry expression used to describe any pearl that is not symmetrical. Typically baroque pearls, whether cultured or natural, will be free form and asymmetrical.
Biwa pearl: Cultured freshwater pearls that are grown by a freshwater mussel located in Lake Biwa in Japan. Recently, the U.S. Federal Trade Commission ruled that the term "Biwa pearl" may be used to describe any freshwater pearl that comes from any freshwater mussel in Japan.
Black-lip oyster: An oyster, known scientifically as Pinctada margaritifera, found in the South Pacific, in areas such as French Polynesia, Okinawa, and the Cook Islands. This particular species of oyster grows to about twelve inches in diameter and produces a wide range of dark-colored pearls commonly called "Tahitian pearls" or "black pearls." The natural colors of pearls grown by this oyster include silver/white, light gray, dark gray, orange, gold, green, blue, purple, and black.
Blemish: A blemish refers to any surface defect on a pearl. Blemishes can include spots, bumps, pits, holes, cracks, chips, wrinkles and dull spots. Blemishes fall into two categories, damaging blemishes and non-damaging blemishes. Non-damaging blemishes include spots, bumps, pits and wrinkles. These types of blemishes do not affect the durability of a pearl but will affect the price. Damaging blemishes, however, such as cracks, holes and chips will only get larger over time and wear and can seriously affect the durability of a pearl.
Button: A shape of a pearl where one side of the pearl is slightly flat.
Choker: An industry standard length of a pearl necklace between 16 to 18 inches in length.
Circles: Concentric rings that form on the surface of a pearl that are concave in appearance. If circles are apparent on more than 1/3 of a pearl's surface then the term "circle pearl" is applied to describe the shape of a pearl. If less than 1/3 of a pearl's surface is covered by circles, then the circle is considered a blemish and not a shape description.
Clean: A term used to describe the absence or relative absence of any blemishes on the surface of a pearl.
Color: A quality/value evaluation category used to describe the color of a pearl. Although color is not particularly an indicator of quality, generally creamy/yellow hues are less valuable than other pearl colors.
Collar: An industry standard length of a pearl necklace between 10 to 13 inches in length that usually rests in the middle of the neck. Collars are sometimes referred to as "dog collars" and are usually made up of two or more strands.
Conch pearl: A pearl produced by a conch, a saltwater mollusk found in tropical waters. Usually conch pearls exhibit orange and pink colors and tend to look similar to pink coral.
Cultured pearl: Any pearl which is grown by a mollusk that contains either a hard bead nucleus or soft tissue nucleus at its center, which has been surgically implanted in a mollusk by human means.
Cultivated pearl: Any pearl which is grown by a mollusk that contains either a hard bead nucleus or soft tissue nucleus at its center, which has been surgically implanted in a mollusk by human means.
Freshwater cultured pearl: Any cultured pearl that is grown by a freshwater mollusk. Freshwater mollusks usually inhabit lakes and rivers, but they can be grown in ponds as well.
Grafting: The process of nucleating a mollusk to produce a pearl. Also termed as nucleation or implantation, grafting requires the human insertion of either a hard bead nucleus or soft mantle tissue into either the body of a mollusk or the mantle tissue of a mollusk. The nucleus or mantle tissue serves as a "seed" or "irritant" to produce a cultured pearl.
Gold-lip oyster: A large species of oyster, from the Pinctada maxima family, that can produce cream to gold-colored South Sea pearls. Gold-lip oysters can be found in the waters off Australia, Indonesia, the Philippines, and Japan.
Imitation pearl: A simulated pearl manufactured entirely by man or machine.
Keshii pearl: A keshii pearl, sometimes referred to as a seed pearl, is a non-nucleated pearl. Keshii pearls form by accident in mollusks (usually saltwater mollusks) as a by-product of the culturing process and thus cannot be considered natural pearls. Keshii pearls can be as small as 1 mm and as large as 10 mm in size.
Lustre: A quality evaluation category used to describe the combination of surface shine (reflectivity) and inner light refraction (depth). Lustre is perhaps the most important of all quality factors and is expressed in terms of high, medium and low lustre. The lustre of a high quality pearl should be bright and capable of sharply reflecting objects near its surface. A dull or chalky lustre indicates poor quality.
Mabe pearl: A half-spherical cultured pearl grown on the inside shell of a mollusk, as opposed to inside a mollusk's body. Mabe pearls are grown by glueing a plastic hemisphere onto the inside of a mollusk's shell. Once the hemispherical nucleus is covered with a sufficient amount of nacre, the pearl is cut away from the inner shell, the bead taken out, and the cavity filled with a substance such as epoxy resin and backed by a mother-of-pearl plate. Mabe pearls are sometimes referred to as blister pearls.
Mantle tissue: The thin tissue membrane that attaches a mollusk to its inner shell. Small pieces of mantle tissue are inserted next to hard bead nuclei to help cultured pearls grow in saltwater oysters, while pieces of mantle tissue are used exclusively (without a hard bead nucleus) in many freshwater mussels to grow cultured pearls.
Matching: The process of matching pearls in terms of lustre, surface, shape, color, and size to assemble a necklace or other piece of pearl jewelry.
Matinee: An industry standard length of a pearl necklace between 20 to 24 inches in length.
Millimeter: A metric measurement of length used to determine a pearl's size. Often expressed as "mm," whereby one "mm" equals 1/25 of an inch.
Momme: A Japanese weight measurement used for pearls. One momme equals 3.75 grams or 18.75 carats.
Nacre: A calcium carbonate-based crystalline substance secreted by mollusks to form mother-of-pearl, pearls, and cultured pearls. Nacre secretion by a mollusk is usually a defense mechanism triggered by the intrusion of a foreign object into the body of an oyster.
Nucleus: Typically a small, round piece of polished shell from an American freshwater mussel used as an irritant or core in all saltwater cultured pearl production. In freshwater cultured pearl production, a nucleus is usually a small piece of soft mantle tissue from another freshwater mussel.
Nucleation: The process of nucleating a mollusk to produce a pearl. Also termed as grafting or implantation, nucleation requires the human insertion of either a hard bead nucleus or soft mantle tissue into either the body of a mollusk 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.
Opera: An industry standard length of a pearl necklace between 28 to 32 inches in length.
Princess: An industry standard length of a pearl necklace between 17 to 19 inches in length.
Rope: An industry standard length of a pearl necklace over 45 inches in length.
Shape: A quality evaluation category used to describe the shape of a pearl. The most valuable pearls are round. However, other shapes of pearls include off-round, drop, oval, button (one flat side), circled, semi-baroque and baroque (asymmetrical/freeform). Freshwater cultured pearls are grown in all of the aforementioned shapes as well as stick, angel-wing, cross and coin (flat on two sides) shapes.
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 lustre, surface, shape, color and size.
South Sea cultured pearl: An industry name for large cultured pearls grown in the white-lip oyster (Pinctada maxima). South Sea cultured pearls generally range in size from 8 mm to over 22 mm in some cases and can range in color from white to gold, with silver, cream, and champagne in between.
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.
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.
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.