Nata Heng Schluessel, GG logo Roland Schluessel, FGA

How to describe the quality of a gemstone

CLARITY:

Flawless = No inclusions visible with a 10x loupe.
Eye clean = No inclusions visible with the unaided eye.
Very slightly included (consider position and color of inclusions).
Slightly included (consider position and color of inclusions).
Included = Affects slightly the stone’s transparency.
Heavily included = Affects considerably the stone’s transparency.
Extremely included = Stone is semi transparent.

Note: If present, also consider color/growth zoning.

COLOR:

A color of a gemstone can be described by using the terms HUE, TONE and SATURATION. (Source: GIA Gemset Manual)

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1

2

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COLOR HUE:
(basic sensation of a color)
COLOR TONE:
(lightness or darkness of a hue)
COLOR SATURATION:
(strength/intensity or purity of a hue)
red-purple or purple red
strongly purplish red
slightly purplish red
red
orangey red
red-orange or orange red
reddish orange
orange
yellowish orange
orangey yellow
greenish yellow
yellow-green or green-yellow
strongly yellowish green
yellowish green
slightly yellowish green
green
very slightly bluish green
bluish green
very strongly bluish green
green-blue or blue-green
very strongly greenish blue
blue
violetish blue
violet
bluish purple
purple
reddish purple
0 - colorless or white
1 - extremely light
2 - very light
3 - light
4 - medium light
5 - medium
6 - medium dark
7 - dark
8 - very dark
9 - extremely dark
10 - black
1 - grayish or brownish
2 - slightly grayish or brownish
3 - very slightly grayish or brownish
4 - moderately strong
5 - strong
6 - vivid

LIFE – BRILLIANCY – SPARKLING – EXTINCTION:

The patterned effect that serves as the basis of the color and beauty of a faceted gemstone can be defined as “mosaic pattern”. The beauty of a faceted gemstone is created by movement of the tones and shapes within a well-balanced mosaic pattern.

When moving a gemstone the observer can estimate the percentage that looks black. These areas of black reflection are called “extinction areas”. The lower the extinction, the better the “life” and overall quality of the gemstone.

The expected extinction depends upon the gemstone species and its color tone. A blue Sapphire has usually more extinction areas than a Ruby and an Emerald has generally less extinction areas than a Ruby. Fancy color Sapphires, Tourmalines and Aquamarines display usually small extinction areas if they are well cut.

EXAMPLE FOR A BLUE SAPPHIRE:

Less than 20% extinction = excellent life of color
20% to 30% extinction = very good life of color
30% to 50% extinction = good life of color
40% to 60% extinction = medium life of color
60% to 80% extinction = poor life of color
More than 80% extinction = very poor life of color

Other criteria for helping to describe the quality of a color gemstone are:

SHAPE, quality of CUT, CARAT WEIGHT and type/extent of ENHANCEMENT

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