Glossary of Pearl Terms G

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Gajamukta: So-called pearl said to come from the heads or tusk sockets of elephants; also called elephant pearl.

Gajamuthu: Same as gajamukta and elephant pearl.

Ganglia or ganglions, plural, ganglion, singular: Groups of nerve cells that constitute the primitive nervous system of a bivalve mollusk.

Gastropod: Univalve mollusk, including land and sea snails, with a head and eyes and a foot to move about.

Gamma ray irradiation: Method of darkening freshwater pearls and the mother-of-pearl core of bead-nucleated saltwater pearls by altering the trace element manganese.

Gem quality/grade: Perfectly clean pearl exhibiting fine color and luster.

Giant clam: Tridacna gigas, a non-nacreous natural pearl producer that is listed as a threatened species in Appendix II of the international CITES treaty.

Giant clam nucleus: Bead nucleus formed from the shell of a giant clam. It is a violation of the international CITES treaty for any signatory nation to import or permit the use of wild giant clams for any purpose.

GIE Perles de Tahiti: (GIE = Groupement d'Interet Economique) Government organization responsible for regulating the Tahiti cultured pearl industry and promoting its products. GIE ceased operations in 2007.

GIE Poe Rava Nui: Cooperative of Tahitian pearl producers and wholesalers.

GIA: Gemological Institute of America, nonprofit school and gemological laboratory founded in 1931; headquarters are in Carlsbad, California.

GIA pearl grading system: Grading system for cultured pearls; developed by GIA in the late 1990s.

Glacier pearl: Imitation abalone pearl made from abalone shell.

Glass nucleus: Bead used to produce imitation pearls like the Majorica and Mallorca brands.

Glochidia: Freshwater mussel larvae. This larval stage is known to settle on the gills of a host-fish.

Gold-lip pearl oyster: the Pinctada maxima mollusk used to produce of natural-color golden South Sea pearls. The outer edges of the shell interior are golden in color.

Gonad: the reproductive organ of an oyster or mussel. It's the general organ where a bead nucleus or nuclei and donor-mollusk tissue piece or pieces are implanted to produce cultured pearls.

Graduated strand: Strand of pearls with 3 mm or more gradation from the ends to the middle, with the largest pearl as the center.

Graft tissue: Donor-mollusk mantle tissue piece implanted with or without a bead nucleus in a host mollusk to produce a cultured pearl.

Graft: To insert a piece of graft tissue with or without a bead nucleus in a host mollusk to induce it to produce of a cultured pearl.

Grain: Unit of weight associated with natural pearls. One grain equals 0.25 carat.

Greffon: Term used in French Polynesia to describe the grafting process.