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I Edit 16 terms found

I
A grade in GIA’s Color Grading System…. in the middle of the “Near Colorless” category.
Ideal Cut
A Round Brilliant Cut diamond that cut to optimal proportions, with optimal polish and symmetry. There is no universally accepted standard for an Ideal Cut. The most commonly mentioned proportions when talking about an Ideal Cut is the proportioning that was mathematically determined by Marcel Tolkowsky in 1919. See Diamond Cut
IGI
International Gemological Institute. A gemological laboratory which offers a diamond grading reports also written appraisals.
Illusion setting
A head designed to make the diamond that is set into it look larger than it actually is…. hence it is giving the “illusion” of a larger diamond. The metal that surrounds the stone usually has an intricate design.
Incabloc
The best known of the various competing shock absorbers for watches, it is manufactured by Potescap SA and considered an industry standard.
Included (I1,I2,I3)
“I” in GIA’s Clarity Grading System… “contain inclusions which are obvious to a trained grader under 10X, can often be easily seen face-up with the unaided eye, seriously affect the stone’s potential durability, or are so numerous they affect transparency and brilliance”. I1 usually has inclusions that are visible to the unaided eye and at the end of the I3 grade the diamond can no longer be considered gem quality.
Included Crystal
A mineral crystal (many times it’s another diamond, but it could also be one of many different minerals) contained inside of a diamond. Include crystals can be almost any size, colored or colorless, and can occur alone or in groups. Dark included crystals are often called “carbon spots” or just “carbon”, but it’s an incorrect term when referring to these diamond inclusions.
Inclusions
Foreign matter that is “included” within a stone. This may be a foreign body such as a crystal, a gas bubble or a pocket of liquid. There are many varieties of inclusions and they are important visual clues for identifying the type of gemstone and for identifying the origin of the stone.
Indices
Another term for the hour markers on a watch’s dial.
Indicolite Blue tourmaline
From bright blue hues to bluish green colors, indicolite tourmaline is one of the rarer tourmaline colors.
Industrial Diamonds
Non-gem quality diamonds used in drills and other tools.
Internal Graining
Internal indications of irregular crystal growth. May appear milky, like faint lines or streaks, or may be colored or reflective.
Internally Flawless (IF)
no inclusions when examined by a skilled grader, and only insignificant blemishes under 10X.
Invisible Set Diamonds
A skilled method of setting square gemstones into two rows or more with no metal showing between the rows.
Iridescence Effect
caused by the interference of light on thin films within the gemstone.
Irradiated Diamond
A diamond which has been exposed to a stream of accelerated electrons and then heated in order to alter its color. See Color Enhanced Diamonds.