GEMSTONE COLOR GRADING

Color has three main components: Hue, Tone and Saturation:


Hue - Described as the shade, tint or sensation of a color. The GIA   has 31 Hues which can be used to describe viturally all colored gemstones. The complete GIA has 324 sample hue colors with varying Tones and Saturations.

Tone - 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 - Described as the strength or purity of a Hue. The GIA Saturation Scale is from 1 to 6. The lower numbers such as 1, 2 or 3 of warm colors such as red, orange or yellow and 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.


GIA Hue, Tone and Saturation Scales

HUES

R                red
oR             orangy red

h_or.gif (806 bytes)
RO/OR     red-orange or orange-red h_or-ro.gif (806 bytes)
rO              reddish orange h_ro.gif (806 bytes)
O               orange h_o.gif (806 bytes)
yO             yellowish orange h_yo.gif (806 bytes)
oY             orangy yellow h_oy.gif (806 bytes)
Y               yellow h_y.gif (806 bytes)
gY             greenish yellow h_gy.gif (806 bytes)
YG/GY    yellow-green or green-yellow h_yg-gy.gif (806 bytes)
styG         strongly yellowish green h_styg.gif (806 bytes)
yG           yellowish green h_yg.gif (806 bytes)
slyG         slightly yellowish green h_slyg.gif (806 bytes)
G              green h-g.gif (806 bytes)
vslbG       very slightly bluish green h_vslbg.gif (806 bytes)
bG           bluish green h_bg.gif (806 bytes)
vstbG       very strongly bluish green h_vstbg.gif (806 bytes)
GB/BG    green-blue or blue-green h_gb-bg.gif (806 bytes)
vstgB       very strongly greenish blue h_vstgb.gif (806 bytes)
gB           greenish blue h_gb.gif (806 bytes)
vslgB       very slightly greenish blue h_vslgb.gif (806 bytes)
B              blue h_b.gif (806 bytes)
vB           violetish blue h_vb.gif (806 bytes)
bV           bluish violet h_bv.gif (806 bytes)
V              violet h_v.gif (806 bytes)
bP           bluish purple h_bp.gif (806 bytes)
P              purple h_p.gif (806 bytes)
rP             reddish purple h_rp.gif (806 bytes)
RP/PR     red-purple or purple-red h_rp-pr.gif (806 bytes)
stpR        strongly purplish red h_stpr.gif (806 bytes)
slpR        slightly purplish red h_slpr.gif (806 bytes)

 

TONE

0     c - Colorless or White
1     exl - Extremely light
2     vl - Very light
3     l - Light
4     ml - Medium light
5     m - Medium
6    md - Medium dark
7    d - Dark
8     vd - Very dark
9     exd - Extremely dark
10   bl - Black		  
 
 
 
 
 
 
 
 
 
 

Tone Scale

 tone.bmp (105894 bytes)
  1 2 3 4 5 6 7 8 9 10

 

SATURATION

1    gr(br) - grayish (brownish)
2    slgr - slightly grayish (brownish
3    vslgr - very slightly grayish (brownish)
4    mst - moderately strong
5    st - strong
6    v - vivid

Warm Colors

 satur8_w.bmp (107382 bytes)
  1 2 3 4 5 6

Cool Colors

 satur8_c.bmp (99254 bytes)

 

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