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Diamond color grading chart. Refers to a grading scale for diamonds in the normal color range used by internationally recognized laboratories (GIA, IGI, & GCAL by Sarine for example). The scale ranges from D which is totally colorless to Z which is a pale yellow or brown color.
The Gemological Institute of America (GIA) is a nonprofit institute based in Carlsbad, California. It is dedicated to research and education in the field of gemology and the jewelry arts. [1] Founded in 1931, GIA's mission is to protect buyers and sellers of gemstones by setting and maintaining the standards used to evaluate gemstone quality.
Gem identification is basically a process of elimination. Gemstones of similar color undergo non-destructive optical testing until there is only one possible identity. Any single test is nearly always only indicative. For example: The specific gravity of ruby is 4.00, glass is 3.15–4.20, and cubic zirconia is 5.6–5.9 . So one can easily ...
Some of the colored diamonds, such as pink, are very rare. A chemically pure and structurally perfect diamond is perfectly transparent with no hue, or color. However, in reality most gem-sized natural diamonds are imperfect. The color of a diamond may be affected by chemical impurities and/or structural defects in the crystal lattice. Depending ...
His objective throughout instrument development at GIA was to provide jewelers with practical tools that could help them in the day-to-day operation of identifying gemstones. By the 1970s, the GIA Gem Trade Laboratory staff was examining large numbers of gemstones, including the grading of diamonds and the identification of colored stones and ...
Emerald is a gemstone and a variety of the mineral beryl (Be 3 Al 2 (SiO 3) 6) colored green by trace amounts of chromium or sometimes vanadium. [2] Beryl has a hardness of 7.5–8 on the Mohs scale. [2] Most emeralds have many inclusions, [3] so their toughness (resistance to breakage) is classified as generally poor. Emerald is a cyclosilicate.
Gemstone pricing and value are governed by factors and characteristics in the quality of the stone. These characteristics include clarity, rarity, freedom from defects, the beauty of the stone, as well as the demand for such stones. There are different pricing influencers for both colored gemstones, and for diamonds.
Gemstones of the World revised 5th edition, 2013 by Walter Schumann ISBN 978-1454909538 Smithsonian Handbook: Gemstones by Cally Hall, 2nd ed. 2002 ISBN 978-0789489852 hide