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G

G.I.A. - The Gemological Institute of America. A non-profit organization specializing in grading diamonds and gemstones. Known as the preeminent laboratory for impartial value grading.

Girdle - The narrow rim around a gemstone. The girdle is measured as the largest diameter of the stone.

Girdle width - The proportion of the girdle to the rest of the stone. Too thin a girdle leaves the stone susceptible to cracks and breakage, while a girdle too thick will have reduced brilliance and fire.

Gold - The most malleable of precious metals, gold will not corrode, tarnish or rust.

Gold filled - Any metal covered by a thin layer of gold. The layer must be at least 10k gold and 1/20th of the total weight of the piece.

Gold plate - Essentially the same as gold filled, except the gold content can be less than 1/20th the total weight.

Grade - The systems for valuing diamonds as compared to a master set of stones.

H

Half pearls - Unusually small pearls that have been cut in half to use for border decoration on jewelry pieces.

Head - The part of a jewelry setting that holds a solitaire stone. The head shape is determined by the shape of the stone, and the head size range is dependent on the size of the stone it must hold.

Heat treatments - Almost all rubies and sapphires on today's market have been heat treated for color enhancement. This is a permanent treatment, and therefore totally accepted in the trade.

Hue - The basic color of a colored stone. The pure color of the spectrum by which any variation in a given stone is judged.

I

I.G.L. - The Independent Gemological Laboratories Inc., recognized as a reputable resource for grading gemstones.

Inclusions - Any and all internal flaws naturally occurring in gemstones.

Irradiation - A treatment done on pearls and some colored stones for color enhancement that is not always permanent and must be stated on your bill of sale.

Irritant - The mother of pearl, or other substance, implanted into oysters in order to produce pearls.