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Evaluating
Gemstones

Grading Gemstones -- a Brief Introduction

The Gemological Institute of America (GIA) terms by which Topazery gemstones are graded are briefly explained on this page. Like diamonds, gemstones are graded by color, cut, clarity and carat weight. When grading a gemstone, a gemologist measures a gemstone's weight in carats, and the gemstone's dimensions [length, width, and depth] in millimeters. Clarity and color are also evaluated. Color in gemstones is composed of three different qualities: hue, tone, and saturation.



Clarity Categories for Gemstones

Clarity is a gemstone's relative freedom from clarity characteristics. The clarity grade is based on how visible inclusions are and how they affect the gemstone's beauty and durability. Some gemstones tend to have more inclusions than others. For this reason, clarity ranges for gemstones are grouped into three types: Type I, Type II, and Type III. Type I stones are usually eye-clean with no inclusions visible to the naked eye. Type II stones typically show some eye-visible inclusions that don't detract from the gem's overall beauty. Type III stones are almost always included and show eye-visible inclusions.


VVS, Eye-Clean VS, Slightly Included SI1-SI2, Moderately Included I1-I2, Heavily Included I3, Severely Included
Type I The stone appears clean to the unaided eye. Minute inclusions are difficult to see without a 10x loupe. Minor inclusions are somewhat easy to see without a 10x loupe. Inclusions are prominent. Prominent inclusions have a severe impact on appearance, durability, or both.
Type II The stone appears clean to the unaided eye. Minor inclusions are somewhat easy to see with the unaided eye. Noticeable inclusions apparent to the unaided eye. Inclusions are prominent. Prominent inclusions have a severe effect on appearance, durability, or both.
Type III The stone appears clean to the unaided eye. Noticeable inclusions apparent to the unaided eye. Obvious inclusions very apparent to the unaided eye. Inclusions are prominent. Prominent inclusions have a severe impact on appearance, durability, or both.


Color in Gemstones

Color is the first thing you notice about a gemstone. Color is mainly caused by the gem's selective absorption of certain wavelengths of light. Gemologists refer to this color as the gem's body color. In gemstones, color consists of three components: hue, tone and saturation.

Hue is the first impression of a color and is what you see when you first look at a gem. The GIA gemstone grading system uses 31 hues to describe color in a gemstone.

Tone is the lightness or darkness of color and ranges from light to medium to dark. Three key standards are 3 (light), 5 (medium), and 7 (dark).

Saturation is the intensity of a gemstone's color and is measured from dull to strong to vivid. The GIA uses 6 saturation measurements.



Color Hues for Gemstones

Purple P
reddish Purple rP
Red-Purple or Purple-Red RP/PR
strongly purplish Red stpR
slightly purplish Red slpR
Red R
orangey Red oR
Red-Orange or Orange-Red RO/OR
reddish Orange rO
Orange O
yellowish Orange yO
orangey Yellow oY
Yellow Y
greenish Yellow gY
Yellow-Green or Green-Yellow YG/GY
strongly yellowish Green styG
yellowish Green yG
slightly yellowish Green slyG
Green G
very slightly bluish Green vslbG
bluish Green bG
very strongly bluish Green vstbG
Green-Blue or Blue-Green GB/BG
very strongly greenish Blue vstgB
greenish Blue gB
very slightly greenish Blue vslgB
Blue B
violetish Blue vB
bluish Violet bV
Violet V
violetish Purple vP


Tones for Gemstones

2 very light
3 light
4 medium light
5 medium
6 medium dark
7 dark
8 very dark


Gemstone Saturation Scale

Warm colors brownish slightly brownish very slightly brownish moderately strong strong vivid
Tone 1 2 3 4 5 6
Cool colors grayish slightly grayish very slightly grayish moderately strong strong vivid

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