Akoya: (pincata martensi fucata). A Japanese oyster used in the culture of Akoya pearls.
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: Cultured fresh-water pearls that are grown by a fresh-water mussel located in Lake Biwa in Japan.
Black-lipped: (pinctada margaritifera). Oyster found in the waters around Tahiti with black shell edges, used in the culture of South Sea black pearls.
Blister: Pearl attached to the shell of the host mollusc. These can occur naturally when a pearl sac bonds with the upper mantle or by human intervention when a hemispherical nucleus is attached to the inner shell by a grafting technician.
Carat: A weight measure sometimes used for natural pearls predominantly in Europe. It equals 200mg. It is not to be confused with the gold measure.
Choker: A strand of unknotted pearls, that lies above the collar bone, 14 to 16 inches in length (35 to 41 cm). A tolerance in pearl size of only 0.5mm is accepted.
Colour: A quality/value evaluation category used to describe the colour of a pearl. Pearl colour is influenced by the type of oyster.
Collier or Graduated Strand: Row of pearls measuring 43cm where the largest pearl is found in the middle and the other pearls then diminish in size, either side, to the clasp.
Cultivation: The process from the seeding of the oyster or shell through to the harvest of the cultured pearl.
Cultured Pearl: Pearl produced by the human insertion of a bead, a tissue graft, or a bead and tissue graft into a fresh-water mussel or salt-water mollusc.
Gold-lipped: Pinctada maxima oyster used to produce of natural-colour gold South Sea pearls. The outer edges of the shell interior are gold in colour.
Hama-age: The highest quality of newly harvested cultured Akoya pearls in Japan.
Ikecho: Japanese name for the Biwa pearl mussel, hyriosis schlegeli.
Imitation: Any material that simulates the appearance of a cultured or natural pearl.
Kan: Historical Japanese weight unit used to value pearls.
One kan equals 1,000 momme or 3.75 kg.
Karasu: Term for the cristaria plicata, fresh-water pearl mussel found in the river Chang in China.
Keshi: Japanese term for poppy seed.
Originally, the term referred to a small natural or cultured pearl.
Korn: A weight measure for natural pearls. One korn equals 0.05g or 0.25 carat.
Lustre: Quantity and quality of light reflected from the surface or just under the surface of a natural or cultured pearl.
Mabe: A half-spherical cultured pearl grown on the inside shell of an oyster found in Japan or south-east Asia.
Majorca: Island off Spain and the term used for imitation pearls.
Mantle: Organ lining the shell of fresh-water and salt-water molluscs.
Small pieces of mantle tissue are inserted next to hard bead nuclei to help cultured pearls grow.
Momme: A Japanese weight measurement used for pearls. One momme equals 3.75 g.
Mother-of-pearl: Iridescent layer lining the inner shell of some mollusc species.
Nacre: Substance that a mollusc layers around an irritant to form a pearl.
Natural Pearl: Organic gem created in a mollusc without human intervention.
Nucleus: Bead implanted in a host oyster, most often with mantle tissue,
to become the core of a cultured pearl.
Opera: An industry standard length of a pearl necklace between 70 - 90 cm in length.
Orient: Optical phenomenon that produces iridescent colours on the surface of some natural and cultured pearls.
Oyster: Common name for bi-valve molluscs either fresh-water or salt-water varieties.
Pearl: Usually refers to a natural pearl where no qualifying adjectives are present.
Princess: An industry standard length of a pearl necklace between 43 - 48 cm in length.
Penguin Wings: (pteria penguin). Species of oyster originally used to produce assembled cultured Mabe blister pearls.
Rope: An industry standard length of a pearl necklace over 115 cm in length.
Sankakuho: (triangular mollusc). A species of mollusc used for the culture of Chinese fresh-water pearls.
Sautoir: A strand of pearls separated by knots. Typically two sautoir are used to make up a choker usually about 85cm in length.
Shape: An important factor when considering a piece of jewellery.
Size: An important factor in the classification of all pearls.
Pearls are usually classified in increments of 0.5mm.
Silver-lipped: (pinctada maxima). An oyster that has silver rather than gold inner shell edges. Used to culture South Sea pearls.
South Sea Pearls: Generic term for natural or cultured pearls produced by the pinctada maxima and pinctada margaritifera oysters.