Colours
Color has three main components: Hue, Tone and Saturation.
Hue is described as the shade, tint or sensation of a color. The GIA GemSet has 31 Hues which can be used to describe viturally all colored gemstones. The complete GIA GemSet has 324 sample hue colors with varying Tones and Saturations.
Tone is described as the relative lightness or darkness of a Hue. The GIA Tone Scale is divided into 11 grades, 0 to 10, with 0 being colorless to 10 being black.
Saturation is described as the strength or purity of a Hue. The GIA Saturation Scale is from 1 to 6. The lower numbers (1, 2 or 3) of warm colors such as red, orange or yellow tend to look brownish and the cool colors such as blue and green tend to look grayish. Level 4 no longer shows either grayishness or brownishness, while neither is strong or weak. Level 5 is strong and level 6 being vivid, almost over colored.
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GIA Hue, Tone & Saturation Scales |
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How Color is described using the GIA Color Grades for Colored Gemstones. |
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Hue |
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Tone |
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RP/PR |
Red-Purple or Purple-Red | 0 | C – Colorless/white | |
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stpR |
strongly purplish Red | 1 | EXL – Extremely Light | |
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slpR |
slightly purplish Red | 2 | VL – Very Light | |
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R |
Red | 3 | L- Light | |
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oR |
orangy Red | 4 | ML – Medium Light | |
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RO/OR |
Red-Orange or Orange-Red | 5 | M – Medium | |
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rO |
reddish Orange | 6 | MD – Medium Dark | |
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O |
Orange | 7 | D – Dark | |
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yO |
yellowish Orange | 8 | VD – Very Dark | |
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Y |
Yellow | 9 | EXD – Extremely Dark | |
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gY |
greenish Yellow | |||
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YG/GY |
Yellow-Green or Green-Yellow | |||
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styG |
strongly yellowish Green | |||
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yG |
yellowish Green | |||
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slyG |
slightly yellowish Green | |||
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G |
Green | |||
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vslbG |
very slightly bluish Green | |||
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bG |
bluish Green | |||
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vstbG |
very strongly bluish Green | |||
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GB/BG |
Green-Blue or Blue-Green | |||
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vstgB |
very strongly greenish Blue | |||
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gB |
greenish Blue | |||
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vslgB |
very slightly greenish Blue | |||
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B |
Blue | |||
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vB |
violetish Blue | |||
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bV |
bluish Violet | |||
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V |
Violet | |||
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bP |
bluish Purple | |||
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P |
Purple | |||
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rP |
reddish Purple | |||
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Saturation |
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gr(br) |
grayish(brownish) | |||
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slgr(br) |
slightly grayish(brownish) | |||
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vslgr(br) |
very slightly grayish(brownish) | |||
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mst |
moderately strong | |||
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s |
strong | |||
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v |
vivid | |||
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Exceptions (Saturation) |
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pk |
pink | |||
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brn |
brown | |||
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Color by Spectrum Exceptions (Saturation) |
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w |
white | |||
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n |
none, colorless or clear | |||
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b |
black | |||
