Posted on

Glossary of Pearl Terms I

Glossary of Pearl Terms I

I-pearls: Imitation pearls from Izumi, Japan.

icon pearl: Cultured blister pearl produced in the shape of an iconic object by using a nucleus of that shape.

IGI grading system: Cultured pearl grading system developed by the International Gemological Institute in New York in 1993. The system uses 22 reference strands to grade color, luster, nacre, shape and surface according to point values ranging from 1 (lowest) to 30 (highest).

ikecho-gai: Japanese name for the Biwa pearly mussel, Hyriosis schlegeli. Translated to English, ikecho-gai is pond butterfly shell.

image pearl: An image pearl, similar to an icon pearl, is a cultured blister pearl in the shape of an image like a Buddha or a dragon; first cultured in Cristaria plicata (cockscomb) mussels in China in the late 1200s.

imitation pearl: Any material that simulates the appearance of a cultured or natural pearl but does not possess either?s physical properties.

immature pearl: Natural pearl that shows discoloration from a conchiolin core or darkened conchiolin rings.

imperial golds: South Sea pearls from the gold-lip pearl mollusk (Pinctada maxima) that exhibit deep gold color saturation.

Incomparable, The: See Peregrina, La.

indicator pearl: Small South Sea pearl (also known as a baby pearl) harvested from Pinctada maxima after six to eight months so a larger nucleus can be inserted in the existing pearl sac. The pearls are generally small and have thin nacre. Indonesia is the primary producer.

infrared spectroscopy: Method of determining the agents used to change the color of a cultured or natural pearl. It is also used to determine the chemical composition of imitation pearls.

interference: Interference of light by nacre creates the iridescent play of color on the surface of a pearl. Refraction, diffraction and/or thin-film interference occur as light penetrates extremely thin nacre layers.

iridescence: Play of color over the surface of a pearl as interference divides white light into its component colors.

irradiation: Exposing a cultured pearl to gamma rays darkens the nacre of a freshwater pearl or the freshwater mussel bead within a cultured saltwater pearl by affecting the manganese each contains.

Ise pearl: Natural white pearl from Ago Bay, Japan. Cultured akoya pearls eclipsed Ise pearls.