Up until 1949, grading Diamonds was questionable and misleading, with terms like "Blue White" that referred to Diamonds that were "Colorless", instead of what they really were, Diamonds that had a Blue Fluorescence to them.
When grading diamonds 'color' refers to the absence of color in a diamond. The rating scale begins at D (meaning colorless) and ends at Z (meaning having a lot of color).
Diffused natural daylight is one of the best sources for grading diamonds for brilliance. Do not use a bare light bulb or spotlight. This type of lighting can accentuate a diamonds sparkle, it might also create dark shadows in the stone.
Gemological Institute of America (GIA): Founded in 1931 by Roger Shipley, this non-profit organization upholds the highest standards for grading diamonds and other precious gems.
ImaGem Inc. is a manufacturer of equipment for grading diamonds by colour, clarity, carat weight, cut, brilliance, intensity, sparkle, and fluorescence.
Imitation ...
Gemological Institute of America: A non-profit group that has been grading diamonds since 1931. It was founded by Roger Shiply.
Girdle: Graded by thickness, it is the outline of the shape of a diamond.
GIA maintains the highest standards for grading diamonds and other precious gems and it has one of the world's most-respected and well-regarded gemological laboratories.
There are straightforward standards for colour and clarity grading diamonds, but the diamond industry and diamond grading laboratories do not have a set standard when it comes to cut grading, proportions and what constitutes an "Ideal" cut diamond.
Cut
Clarity
Color
Carat weight
These are the criteria jewelers use when grading diamonds, and they're the ones you'll need to understand to buy the right diamond for you.
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.
The unit has two 6000ēK fluorescent bulbs for color grading diamonds against master CZ stone sets.
These institutes are revered for their consistency, stringency, and impartiality when grading diamonds.
Master stones: Polished diamonds, or more recently Cubic Zirconia, of known color grades that are used as comparison when grading diamonds for body color.
In the twentieth century, experts in the field of gemology have developed methods of grading diamonds and other gemstones based on the characteristics most important to their value as a gem.
The reason a microscope is used instead of a hand loupe is not to increase the already very high demands which in any case are very exacting, it should merely give greater reliability to the expert gem tester when grading diamonds.
 See also: Diamond, Clarity, Stone, Jewel, Cut
  
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