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Pearl Glossary

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  • Abalone Blister Pearl
    Natural half-pearl that forms on the inside of an abalone oyster shell rather than within its tissue. Once it is reworked, it is known as a Mabe pearl.
  • Abalone Pearl
    Natural whole pearl formed in the body of an abalone, a univalve mollusk known for its iridescent pearls.
  • Adductor
    Muscle responsible for opening and closing a mollusk shell. Sometimes eaten as a delicacy.
  • Akoya Cultured Pearl
    A pearl produced by inserting a seed into a Pinctada fucata martensi mollusk.
  • Ama
    Historical female pearl divers of Japan. There are 2 kinds: kachido worked alone while the funado worked with a partner, usually the husband.
  • Aragonite
    Calcium carbonate crystals that are stacked in a brick pattern. Aragonite is a component of mother-of-pearl and nacre.
  • Atoll
    A ring of coral that encircles a lagoon. Atolls are considered to be the best place to farm the Pinctada margaritifera mollusk.
  • Baroque
    An irregular or asymmetrical pearl. Freshwater pearls are commonly baroque in shape because they are seeded with tissue rather than a bead.
  • Basra Pearl
    Name given by Indian pearl dealers to freshly harvested natural pearls from the town of Basra, Iraq.
  • Bead-Cultured Pearl
    A pearl grown in freshwater or saltwater that has been started by implanting a bead into a mollusk.
  • Bivalve
    A mollusk with a two-part shell attached by a hinge. Some but not all bivalve mollusks produce pearls.
  • Biwa Pearl
    A freshwater pearl grown in a Hyriopsis schlegeli mussel in Lake Biwa, Japan. Sometimes used incorrectly to describe any freshwater pearl.
  • Black-Lipped Pearl Oyster
    A pearl-producing mollusk that is either a Pinctada margaritifera or a Pinctada margaritifera cumingi.
  • Black Pearl
    A pearl that is naturally dark in color produced by any of the following mollusks: Pinctada margaritifera, Pinctada mazatlanica, or Pteria sterna.
  • Bleaching
    Common whitening treatment applied to most freshwater and cultured Akoya pearls, and sometimes to Tahitian or South Sea pearls.
  • Blemish
    A flaw on the surface of a pearl, including pits and/or humps. Blemishes may be difficult to detect with the naked eye.
  • Blister Pearl
    A pearl that is attached to the shell of the mollusk. It may occur naturally or be done intentionally.
  • Bu
    Historical Japanese linear measurement that is still used today to describe the diameter of a bead nucleus. One bu = 3.03 millimeters.
  • Buffing
    A method of removing organic residue from the surface of a pearl to improve its appearance.
  • Button Pearl
    A dome-shaped pearl with one flat side. Classified as ‘high’ or ‘low’ based on height of dome.
  • Byssus
    Thread-like tissue secreted by bivalve mollusks to attach themselves to a solid surface.
  • Calcareous Concretion
    Many types of mollusks including oysters and conches produce these stone-like growths. All pearls are calcareous concretions, nacreous or otherwise.
  • Calcite
    A natural crystalline form of calcium carbonate. When combined with conchiolin and aragonite, they make up nacre.
  • Carat
    A weight measure sometimes used for natural pearls. A carat = 4 grain, 200 milligrams and 0.007054 ounces.
  • Choker
    A pearl necklace that lies above the collar bone and measures 14-16-inch (35-41 cm) in length.
  • Circled Pearl
    A pearl with raised, concentric rings on its surface, likely due to the pearl rotating during growth.
  • Clam Pearls
    Non-nacreous pearls sometimes found in clams. They are generally low in value.
  • Clean
    The best way to clean pearls is by wiping them with a soft cloth after each wear. Use a damp cloth and mild dish soap only when needed. Let dry before storing.
  • Coating
    A natural or artificial layer applied to pearls to enhance surface quality, luster or other optical effects.
  • Collar
    A pearl necklace measuring 10-13-inch (25-33 cm) in length, slightly longer than a choker.
  • Color
    Pearls come in a rainbow of colors, from classic white to exotic black and every shade in between. Pearls frequently have overtones or a secondary color, including rose, silver, gold, and peacock (a mix of rose, gold, and green).
  • Composite Pearls
    Two conjoined pearls that give the appearance of a single pearl.
  • Conch Pearl
    A non-nacreous pearl produced by a conch shell. Rare and valuable, pink is the most desired color.
  • Conchiolin
    An organic glue-like substance that bonds aragonite and calcite crystals in a mollusk’s shell and creates the iridescent layer of mother-of-pearl.
  • Cortez Pearls
    Pearls cultured in Pteria sterna mollusks in the Sea of Cortez, aka the Gulf of California.
  • Cultured Pearl
    A pearl produced by inserting a bead or tissue graft into a mussel or mollusk. The main difference between cultured pearls and natural pearls is cost, cultured being more affordable.
  • Diffraction
    One way nacre layers split light into rainbow colors, sometimes displayed as an overtone.
  • Dome
    A rounded, convex shape with a flat back that is thickest in the middle and tapers toward the edges.
  • Dyeing
    Artificial coloring of pearls to enhance hue, or to create pearls in colors not found in nature. Pearls are usually dyed after drilling to improve color absorption.
  • Faux Pearl
    Any imitation pearl manufactured by coating a glass or plastic sphere with a pearlescent coating that is sometimes pearl powder.
  • Fluorescence
    A common diagnostic tool used to determine whether a pearl has been dyed.
  • Freshwater Cultured Pearl
    A pearl produced by inserting a bead or tissue graft into a mussel that lives in non-saline water.
  • Freshwater Pearl
    A pearl grown in a mussel that lives in non-saline water. Freshwater pearls tend to have a more freeform shape than saltwater pearls.
  • Gajamukta
    Pearls said to come from the tusk sockets of elephants.
  • Gastropod
    A type of univalve mollusk with a head and eyes, including land and sea snails.
  • Gold-Lip Oyster
    The Pinctada maxima mollusk that produces gold South Sea pearls. The edges of the shell’s interior are golden in color.
  • Gonad
    The reproductive organ of pearl-producing mollusks where the bead or tissue graft is implanted to produce cultured pearls.
  • Graduated Strand
    A strand of pearls in which the pearls increase in size a minimum of 3 mm from end to middle, with the largest at the center.
  • Graft
    The insertion of tissue into a mollusk to produce a cultured pearl.
  • Grain
    A unit of weight used with natural pearls. One grain = 0.25 carat.
  • Greffon
    French Polynesian term to describe the grafting process.
  • Half-Drilled
    A pearl that has been drilled to 2/3 or 3/4 of its diameter in order to be set in a piece of jewelry.
  • Haliotis
    The type of gastropod more commonly known as abalone. The shell is extremely strong with tiny tiles of calcium carbonate stacked like bricks.
  • Hankei
    The Japanese term for a cultured blister pearl, which is a pearl attached to the inner surface of a mollusk shell.
  • Hyriopsis Schlegeli
    The pearl mussel native to Japan used to produce cultured freshwater pearls in Lake Biwa. Also cultivated in China.
  • Imitation Pearl
    Any artificial pearl created by coating a glass or plastic sphere with a pearlescent coating that is sometimes pearl powder.
  • Interference
    Interference of light by nacre creates a variety of colors on a pearl’s surface.
  • Iridescence
    Color play on the surface of a pearl caused by light being split into its component colors.
  • Irradiation
    A process in which a cultured pearl is exposed to gamma rays to darken the nacre.
  • Kan
    Historical Japanese unit used to weigh pearls. One kan = 1,000 momme, 3.75 kilograms or 8.26 pounds.
  • Keshi Pearl
    A small natural or cultured pearl. The term comes from the Japanese word for ‘poppyseed.’
  • La Paz Pearl Oyster
    Before culturing black-lip pearl oysters in French Polynesia became popular, most black pearls came from La Paz Pearl Oysters in Panama or Baja California.
  • La Peregrina
    A natural drop-shaped pearl found in 1513 in the Gulf of Panama by the Spanish explorer Balboa and given to King Philip II of Spain.
  • Linné, Carl Von
    Carolus Linnaeus was the first person to culture whole pearls. He also created the classification system of plants and animals used today.
  • Longline Systems
    Part of the pearl farming process. Lines are stretched between buoys and anchored to the bottom at both ends. Vertical lines (chaplets) with baskets of mollusks are suspended from the longlines.
  • Luster
    The quality and quantity of light reflected from the surface of a pearl. High-quality pearls appear to be illuminated from within. Thicker nacre usually results in better luster.
  • Mabe
    A blister pearl grown in Pteria penguin mollusk, then hollowed out and filled with a substance and backing.
  • Maeshori Treatment
    A deep-cleaning process used in Japan before bleaching Akoya cultured pearls. Also used to describe several processes used to enhance the luster of most Chinese Freshwater and some South Sea pearls.
  • Mantle
    The organ that lines the shell of bivalve mollusks and secretes nacre.
  • Margaritifera / margaritifera
    With a capital ‘M’, a genus of freshwater mussels. With a lowercase ‘m’ (Pinctada margaritifera), a species of black-lip mollusk.
  • Matching
    Refers to a strand in which the pearls are uniform, either in graduated size or all the same size.
  • Matinee
    A pearl necklace measuring 20-24 inches (50-60 cm) in length. Matinees have a slimming effect. It is the classic length for an Akoya pearl necklace.
  • Melo Melo
    Marine gastropod that produces the non-nacreous Melo pearl. Rare and very valuable.
  • Mikimoto, Kichimatsu
    First person to commercially produce round cultured pearls using the Mise-Nishikawa method.
  • Mollusk
    A large and diverse category of invertebrates, some of which produce pearls.
  • Momme
    A Japanese unit of weight for cultured pearls. One momme = 3.75 grams.
  • Mother-of-Pearl
    The iridescent lining of the inner shell of some mollusks. When it coats a bead to form a cultured pearl, it is called nacre.
  • Nacre
    The lovely iridescent substance that forms inside a mollusk and is commonly called mother-of-pearl. Made of aragonite, calcite and conchiolin.
  • Natural Pearl
    A pearl that has formed in a mollusk without human intervention. Very rare and thus valuable.
  • Nautilus Pearl
    Extremely rare pearl from the Nautilus pompilius. Imitation Osmenda pearls are sometimes incorrectly named nautilus pearls.
  • Nishikawa, Tokichi
    Credited, possibly by mistake, with discovering the bead-and-tissue method of pearl culture.
  • Non-Nacreous Pearl
    A natural pearl lacking a nacreous surface. Non-nacreous pearls appear to be denser and more like porcelain.
  • Nucleation
    The process of implanting a bead in a mollusk to become the core of a cultured pearl.
  • Nucleus
    The bead implanted into a mollusk to form the core of a cultured pearl. The most common nucleus is a mother-of-pearl bead.
  • Opera
    A pearl necklace measuring 28-35 inches (70-90 cm) in length. Dramatic and meant for glamorous evening events, opera length necklaces can be worn as a long single strand or doubled.
  • Organic Dyes
    Used to alter the color of cultured and natural pearls. Organic dyes may produce a more original effect, but can be difficult to replicate.
  • Orient
    An optical phenomenon producing iridescence in some pearls. Diffraction, refraction, reflection and thin-film interference may all cause orient.
  • Oriental Pearl
    Historical term for natural pearls from the Red Sea and Persian Gulf.
  • Overtone
    Secondary color on the surface of a pearl created by the nacre splitting light into component colors.
  • Oyster
    Common name for some bivalve mollusks. True oysters do not create nacreous pearls.
  • Peacock
    Hue commonly associated with black pearls. Colors range from dark green-gray to blue-gray with rose and purple overtones.
  • Pearl
    A smooth, lustrous mass formed in certain bivalve mollusks and valued as a gem.
  • Pearl Sac
    Grown to contain an intruder or implanted bead, it deposits nacre to form a pearl.
  • Peeling
    Removing the outer nacre layers of a cultured pearl to improve quality.
  • Pelegrina, La
    A pair of natural pearls with the same name. The first is round and weighs 111.5 grains; the second is drop-shaped and weighs 133.2 grains.
  • Pinctada Fucata Martensi
    Mollusk which produces Akoya pearls. Akoyas were the first pearls to be cultured, which took place in Japan in the 1920s.
  • Pinctada Imbricata
    A general term that encompasses all Akoya mollusks regardless of where they grow.
  • Pinctada Margaritifera
    Black-lip mollusk that produces Tahitian and Cook Island cultured pearls.
  • Pinctada Martensi
    Synonym for Pinctada fucata martensi, a mollusk that produces Akoya pearls.
  • Pinctada Maxima
    The silver- or gold-lip pearl mollusk used to produce South Sea cultured pearls.
  • Pinctada Mazatlanica
    Mollusk native to the Gulf of California and the Pacific Ocean in Mexico and Central America.
  • Pinctada Radiata
    Pearl-producing mollusk with a wide distribution, living in both hemispheres and most oceans and seas around the world.
  • Princess
    A pearl necklace measuring 17-19 inches (43-48 cm) in length. A modern classic, princess length necklaces are extremely versatile and elegant as they go effortlessly from day to evening.
  • Red Tide
    Overproduction of algae, also called algal bloom, that can weaken or kill mollusks by consuming all the oxygen in the water and/or poisoning them when the algae die. Red tide is not a true tide, nor is it always red.
  • Refractive Index (RI)
    The measurement of light as it bends from one substance to another, such as from air into nacre. The refractive index of natural and cultured pearls is 1.51-1.66.
  • Rice Pearl
    A small, oblong pearl that resembles a grain of rice. Rice pearls are often strung together in multiple strands.
  • Rope
    A pearl strand measuring more than 45 inches (115 cm) in length. A luxurious length that offers multiple options including looping and knotting.
  • Saltwater Pearl
    A natural or cultured pearl produced by a mollusk living in saltwater. Usually round, saltwater pearls often have a thinner nacre coating than freshwater pearls, which are almost entirely nacre.
  • Sautoir
    A pearl strand measuring more than 36 inches (90 cm) in length. A sautoir is also sometimes called a rope.
  • Scallop Pearl
    A non-nacreous pearl produced by a mollusk of the Pectinidae family. Scallops can swim and are the only migratory bivalve.
  • Seed Pearl
    A tiny natural pearl weighing less than 1/4 grain and usually measuring less than 2 mm in diameter.
  • Shape
    Pearls come in a wide variety of shapes, including round, ringed, button, drop and baroque.
  • Shell Pearl
    Imitation pearl made from a mollusk shell, aka mother-of-pearl. The nacre is pulverized and mixed with other materials to form a pearl.
  • Shinju
    Japanese word for pearl. The method for culturing pearls was developed in Japan in the 1920s.
  • Size
    Describes the diameter of a pearl. Anything below 7 millimeters is called ‘dainty’; 7 to 8 millimeters is a classic ‘wear anywhere’ size; while those greater than 8 millimeters are considered to be ‘luxury.’
  • South Sea Pearl
    Pearl produced by the Pinctada maxima mollusk. Usually larger than the average pearl, South Sea pearls tend to be exceptionally smooth and round, making them highly desirable.
  • Spat
    Saltwater mollusk larva that is old enough to attach itself to a fixed surface but does not yet have a shell.
  • Strombus Gigas
    Also called the queen conch, a large mollusk that lives in the Caribbean. Pearls correspond to the color of the inner surface of the shell and are very rare.
  • Surface
    One of the factors considered when determining the quality of a pearl. A strand of pearls without blemishes is very rare.
  • Tahitian Cultured Pearl
    Produced in French Polynesia by the black-lip (Pinctada margaritifera) mollusk.
  • Tinting
    Diluted dye that produces a slight change in a pearl’s color, often pink.
  • Tone
    A synonym for color, meaning the main color of a pearl. Overtones are secondary colors seen in a pearl.
  • Treatment
    Any action other than polishing that alters a pearl’s appearance, including bleaching, heating, waxing, irradiation, drilling, working and cutting.
  • Unio
    A species of freshwater mussel, many of which produce small, irregular pearls with good luster.
  • Waxing
    A type of treatment used to enhance a pearl’s luster. Sometimes called ‘maeshori.’
  • Working
    The removal of nacre layers from a pearl to improve its appearance. Luster treatments such as working can be difficult to detect with the naked eye.

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