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GIA color grading

GIA color grading is separated to be 3 types. The first one is intensity, or saturation. The second is hue, or color. And the last is tone, or lightness/ darkness. You can see the picture below for comparing the gem's colors.

1) Hue

The hue is the actual color of gemstones ex. red, yellow, green and blue. You can see the chart below.

The GIA hue chart

2) Intensity

The gem's intensity, GIA grading in 6 level of saturation ranging by the grey color saturated of gem color. Please see the chart below.

GIA intensity grading, Zoultier

3) Tone

To describe the darkness or lightness of a colored stone, the GIA system has 9 levels of tone ranging from "very very light" to "very very dark." Please see at the chart below.

GIA's tone chart, Zoultier

With the exception of hue, each of these parameters by themselves are relatively meaningless and they must be used in conjunction to tell the full story of a gem's color quality. Taken together, these three parameters will provide a simple numeric code that can quickly and accurately quantify gemstone color.

GIA blue sapphire's color grading, Zoultier

Example, if you think about "cornflower" color and "royal blue" color of blue sapphire, you can specify the color clearly with other when use the GIA color grading chart.