Nata Heng Schluessel, GG
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)
| 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
