GIA Diamond Grading Standards

GIA created the international grading system for diamonds. Here is a short video showing how the Gemological Institute of America grades diamonds.

GIA Diamond Colour Grading

Diamond Colour Grading Image

Diamond colour grades are alphabetical letter grades from D to Z. The highest prices charged are for D colours. Once a diamond has enough colour, it is considered a “Fancy Colour.” These are graded Z+.

Diamonds are graded by comparing them to diamonds of known colour grades. The comparison diamonds are called “Master Stones.

GIA Diamond Clarity Grading

Diamond Clarity Grades Defined
Flawless (FL) No internal inclusions or external blemishes visible at 10X magnification
Internally Flawless (IF) Very insignificant external blemishes only at 10X magnification
VVS1 Minute inclusions extremely difficult to see at 10X magnification
VVS2 Minute inclusions very difficult to see at 10X magnification
VS1 Minor inclusions somewhat difficult to see 10X magnification
VS2 Minor inclusions somewhat easy to see at 10X magnification
SI1 Noticeable inclusions easy to see at 10X magnification
SI2 Noticeable inclusions easy to see at 10X magnification, may be visible to the unaided eye from the bottom side
I1 Obvious inclusions at 10X mag., and just visible to the unaided eye
I2 Obvious inclusions at 10X mag., and noticeable to the unaided eye. Stone durability is usually affected
I3 Obvious inclusions at 10X mag., and very noticeable to the unaided eye. Durability and transparency are severely affected

GIA Diamond Cut Grading

You may have heard of the “Ideal cut”. This is a term that refers to the proportions of a diamond. An Ideal cut diamond is one that is cut to “Ideal Proportions” as laid out by Marcel Tolkowski. His mathematical work determined the best proportions for a diamond to maximize brilliancy, dispersion and scintillation of a diamond. Recently, the GIA examined thousands of diamonds over a 15 year period and concluded that there are other combinations of proportions that deviate from the ones defined by Tolkowski which yield excellent brilliancy, etc. Today diamonds of a top quality cut grading are referred to by the GIA as “Excellent” rather than “Ideal.” Excellent is a broader term that also refers to finish and minor symmetry and accepts some proportions that may have previously been outside of Ideal proportions. This is not to say the GIA has lowered any standards. It simply came to a conclusion through observation that the Ideal cut definition may have excluded a few diamond proportions which were equally as beautiful. Today, the diamond industry accepts both terms to describe a top quality cut.

GIA Diamond Grading Report

Here is a short video on how to read a GIA Diamond Grading Report.

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