Color Grading System - GIA Gemologists
Sapphire Ring Cohas incorporated the official GIA Sapphire and Ruby color map below. The charts explain the color grading system used by all GIA G.G. gemologists in their color grading of Sapphires & Rubies. The charts illustrate the wide variations in color gradings for Sapphire and Rubies as well as the three main factors which make up Sapphire's color: Hue, Tone & Saturation.
Please feel free to contact us at any time with any questions you may have on Sapphire color grading and how this is used today to give each Sapphire it's final color grade. Understanding these distinctions is important in properly choosing your perfect color in a natural Sapphire or Ruby.
GIA Color Grading Scale
Hue TableThe GIA Colored Stone Grading System includes a description system that uses 31 hue names to describe colored gemstones.
|very slightly greenish blue||vslgB|
|red-purple or purple-red||RP/PR|
|strongly purplish red||stpR|
|slightly purplish red||slpR|
|red-orange or orange-red||RO/OR|
|yellow-green or green-yellow||YG/GY|
|strongly yellowish green||styG|
|slightly yellowish green||slyG|
|very slightly bluish-green||vslbG|
|very strongly bluish||vstbG|
|green-blue or blue-green||GB/BG|
|very strongly greenish blue||vstgB|
ToneThe GIA Tone Scale helps you judge a gem's brightness or darkness. Three key standards to remember are (3) Light, (5) Medium. and (7) Dark.
Saturation ScaleUse the GIA saturation scale to judge a gem's strength of color. In warm colors, weaker saturation of 1, 2, or 3 appears brownish. In cool colors, the same values look grayish. In both warm and cool colors, gems with saturations of 4, 5, or 6 are almost always more valuable if all other factors are equal.
|Name||Cool Color||Scale||Warm Color||Name|
|slightly grayish||slightly brownish|
|very slightly grayish||very slightly brownish|
|moderately strong||moderately strong|