Coloured Gemstone Grading | All About Gemstones
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Coloured Gemstone Grading

Much like a diamond, the various combinations of a stone’s cut, colour, clarity, and carat weight, along with availability and accessibility, determine rarity. You will find a brief description of those features here. These explanations are based on the system for gemstone evaluation established by the Gemmological Institute of America (GIA).

Colour

Colour is the most defining characteristic of a gemstone. Most gemstones occur in a spectrum of colours, while some have more restricted palettes. Since the colour phenomenon in gems is very complex, experts analyse the chromatic options in terms of three essential components: hue, tone, and saturation. Hue is the basic or the primary colour of the gemstone, tone refers to the lightness or darkness of the colour and saturation refers to the purity or intensity of the primary colour.

As a general rule, a bright, intense, pure, rich and vivid colour is always best. The most valuable gemstones are those that exhibit a pure colour with only slight hues of other colours in addition to their primary colour.

The primary colour should be medium, neither too dark nor too light.

While buying gemstones you need to be aware of colour ranges and objective value assessments, but it’s best to rely on your eyes and heart. Select your gemstone by trusting your instincts; if a particular colour speaks to you, by all means listen!

Hue is described as the shade, tint or sensation of a colour. The GIA has 31 Hues and the complete GIA GemSet® has 324 sample hue colours with varying Tones and Saturations. In addition we put RGB (Red Green Blue) and HEX codes for your reference.

KeyCodeNameHEXRGB
RRredFA0303R:250 G:3 B:3
oR oRorangy redEE2102R:238 G:33 B:2
RO/ORred-orange or orange-redFB3E00R:251 G:62 B:0
rO rOreddish orangeFE6000R:254 G:96 B:0
O OorangeF87B00R:254 G:96 B:0
yO yOyellowish orangeF6A400R:246 G:164 B:0
oY oYorangy yellowF7CD00R:247 G:205 B:0
Y YyellowF8F800R:248 G:248 B:0
gY gYgreenish yellowCEE600R:206 G:230 B:0
YG/GY YG/GYyellow-green or green-yellowB0DD00R:176 G:221 B:0
styG styGstrongly yellowish green7BCE00R:123 G:206 B:0
yG yGyellowish green4DC100R:77 G:193 B:0
slyG slyGslightly yellowish green26C200R:38 G:194 B:0
GGgreen00C000R:0 G:192 B:0
vslbG vslbGvery slightly bluish green00BE26R:0 G:190 B:38
bG bGbluish green00BA4AR:0 G:186 B:74
vstbG vstbGvery strongly bluish green00B96FR:0 G:185 B:111
GB/BG GB/BGgreen-blue or blue-green00B893R:0 G:184 B:147
vstgB vstgBvery strongly greenish blue09B4B4R:9 G:180 B:180
vslgB vslgBvery slightly greenish blue0A59AAR:10 G:89 B:170
B Bblue0916A5R:9 G:22 B:165
vB vBvioletish blue0808A0R:8 G:8 B:160
bV bVbluish violet7B0AB4R:62 G:8 B:170
V Vviolet7B0AB4R:123 G:10 B:180
bP bPbluish purpleC70BC7R:199 G:11 B:199
P PpurpleD40CB1R:212 G:12 B:177
rP rPreddish purpleE90A9ER:233 G:10 B:158
RP/PR RP/PRred-purple or purple-redF50E80R:245 G:14 B:128
strpR stpRstrongly purplish redF80E5CR:248 G:14 B:92
slpR slpRslightly purplish redF20E33R:242 G:14 B:51
R RredFA0303R:250 G:3 B:3
Pk Pkpink (exception)FFDFDFR:255 G:223 B:223
Brn Brnbrown (exception)B7770DR:183 G:119 B:13
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