Glossary of Pearl Terms C

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Cabochon: In gemology, a usually round or oval shaped gemstone with a domed top and flat bottom; hence, a pearl of that shape.

Calcareous concretion: Whether nacreous or not, all pearls are calcareous concretions.

Calcite: A form of natural calcium carbonate that, together with aragonite and conchiolin, makes up the structure of nacre.

Calcium carbonate: Pearls are mainly composed of calcium carbonate (CaCO3) and other elements and substances.

Candling: Examining a pearl in front of a focused light source to determine if it shows the layered structure that proves it contains a bead nucleus.

Carat: A weight measure sometimes used for natural pearls. It equals 4 grains, 200 milligrams or 0.007054 oz.

Cassis pearl: Yellowish brown pearl produced by gastropods of the genus Cassis.

Cave pearls: Stalactite pearls of a brown color, concentric layers and, sometimes, a pearly luster.

Ceylon pearl mollusk: The Pinctada imbricata mollusk known for producing natural pearls in the Gulf of Mannar, the Red Sea and the Persian Gulf. According to some taxonomists, it was formerly considered a distinctive species known as Pinctada radiata.

Chau: Historical unit of weight used in the natural pearl trade in India, also called chov.

Chaplets: Line extensions of a pearl farm's long-line system that are secured to the shells.

Chemical dyes: A method used to alter the natural color of a cultured pearl.

Cherry: A reddish overtone often found on pearls produced by Pinctada margaritifera.

Chloride vapor deposition: A superficial pearl coating/coloring agent experimented with in the 1960s.

Choker necklace: A strand of pearls that lies above the collar bone, 14 to 16 inches in length (35 to 41 cm).

Chov: See chau.

CIBJO: (Confederation Internationale de la Bijouterie, Joaillerie et Orfebrerie), also known as the World Jewellery Confederation, is an international confederation of jewelry, gemstone, horology, and silverware trade organizations. CIBJO publishes The Pearl Book: Natural, Cultured & Imitation Pearls: Terminology & Classification.

Circled pearl: Pearl with raised concentric rings around its surface, thought to be produced by the developing pearl rotating during growth. Also known as a Circlé or "ringed" pearl.

Circlé pearl: See above.

Clam pearl: non-nacreous pearl found in clams.

Coating: A layer of artificial or natural substance applied to pearls to enhance luster, surface quality or to produce other optical effects.

Coconut pearl: So-called "pearl" said to be found in coconuts.

Coin pearl: Bead-and-tissue-cultured pearl shaped like a coin.

Collar: A strand of pearls that measures 10 to 13 inches (25 to 33 cm).

Composite cultured blister pearl: See Mabe.

Composite pearl: Two separate pearls conjoined to give the appearance of a single pearl.

Concentric structure: The layering of calcium carbonate crystals that is characteristic of natural pearls, tissue-cultured pearls, bead-cultured pearls, and the nacre layer of bead-and-tissue-cultured pearls.

Conch pearl: non-nacreous pearl produced by the "Queen conch" Lobatus(=Strombus) gigas.

Conchiolin: The organic substance that acts like glue, binding calcite, and aragonite crystals together.

Condari: Historical Chinese unit of weight used to evaluate pearls; associated with the weight of a grain of wheat or rice.

Cool hues: Colors from reddish purple to greenish blue to yellowish green from the GIA color reference chart.

Coque de perle: Imitation pearl made from the Nautilus shell (also see Osmena pearl).

Corn flake pearl: Second generation pearl that the Chinese mistakenly call "keshi". They are shaped like breakfast cereal corn flakes.

Cortez pearls: Trade name for the pearl cultured produced in the "Rainbow Lip Pearl Oyster" or Pteria sterna in the Gulf of California, Mexico, which is also called the Sea of Cortez.

CP&J City: China Pearls and Jewelry City. The world's largest pearl and jewelry trade center; in Shanxiahu, Zhuji, Zhejiang, China. The first phase opened in April 2008.

Cristaria plicata: The cockscomb mussel first used in Japan and China in cultured freshwater pearl production.

Cross shape: Tissue-cultured pearl grown in the shape of a cross.

Cultured pearl: Pearl produced by the human insertion of a bead, a tissue graft, or a bead and tissue graft in a freshwater mussel or saltwater mollusk.