Colour of Gemstones

There are three main components to think about when describing colour for coloured gemstones: Hue, Tone and Saturation.

Hue is described as the shade, tint or sensation of a colour. The GIA GemSet‚ has 31 Hues which can be used to describe virtually all coloured stones. The complete GIA GemSet‚ has 324 sample hue colours with varying Tone and Saturation.

Tone is the relative lightness or darkness of a Hue. The GIA Tone Scale is divided into 11 grades, 0 to 10; 0 colourless to 10 black.

Saturation is described as the strength or depth of a Hue. The GIA Saturation Scale is from 1 to 6. The lower numbers 1, 2 or 3 are for warm colours such as red, orange or yellow and tend to look brownish. The cool colours such as blue and green tend to look grayish. Level 4 no longer shows gray or brown - neither strong nor weak. Level 5 is strong and level 6 contains vivid, almost over coloured stones.



                    GIA Hue, Tone & Saturation Scale
Hue                                                                                                         Tone

rp/pr red-purple or purple-red 0 c - colourless/white
stpR strongly purplish red 1 exl - Extremely light
slpR slightly purplish red 2 vl - Very light
R red 3 l - Light
oR orangy red 4 ml - Medium light
ro/or red-orange or orange-red 5 m - Medium
ro reddish orange 6 md - Medium dark
o orange 7 d - Dark
yo yellowish orange 8 vd - Very dark
y yellow 9 exd - Extremely dark
gy greenish yellow
yg/gy yellow-green or green-yellow
styg strongly yellowish green
yg yellowish green
slyg slightly yellowish green
g green
vslbg very slightly bluish green
bg bluish green
vstbg very strongly bluish green
gb/bg green-blue or blue-green
vstbg very strongly greenish blue
gb greenish blue
vslgb very slightly greenish blue
b blue
vb violetish blue
bv bluish violet
v violet
bp bluish purple
p purple
rp reddish purple


Saturation

gr(br) grayish(brownish)
slgr slightly grayish(brownish)
vslgr very slightly grayish(brownish)
mst moderately strong
s strong
v vivid


Exceptions

pk pink
brn brown


Colour by               Exception
Spectrum

w white
n none, colourless or clear
b black

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