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Color Grading of Tanzanite
Though tanzanite is perhaps the most attractive and sought after colored gemstone, its wonderful color is a cause of much of confusion in the minds of gem-lovers. Especially since when the news is out that tanzanite will soon be extinct and so everybody started running after the lovely gemstone, quite an enigma was created regarding how to identify a high-quality tanzanite based on the color-grading system. While for several years marketing terms like ‘A’, ‘AA’ and ‘AAA’ are being used for grading tanzanite, buyers are still in puzzlement regarding just what are they all about!
Well, it will be interesting as well as enlightening to understand first some terms in tanzanite color grading system.
Hue is the shade or tint of a color. GIA (Gemological Institute of America) identifies about 30 hues and their complete color scale, which is also known as GIA Gem Set, has more than 320 hues with different levels of tone and saturation. You will have to just keep in mind that tanzanite ‘hue’ means its basic coloration.
Tone and Saturation
Tone is the term used to denote the lightness or darkness of the hue. As per GIA scale there are 11 tones, 0 to 10, with 0 being colorless and 10 being the darkest.
Saturation is the strength of a hue and is considered to be the most important factor in grading tanzanite by most gemological professionals. GIA scale has decided the levels of saturation from 1 to 6. The lower levels, 1, 2 and 3 are of warm colors like red, orange or yellow, while level 5 is strong and level 6 is vivid or rather over-colored. The warm colors tend to look brownish, while the cool colors like green or blue tend to look grayish. Level 4 is neither strong nor weak and hence exhibits neither brownish nor grayish hue.
Standardized GIA Color Ratings for Tanzanite
The GIA color scale includes a letter or a set of letters followed by numbers. The letters are acronyms for the visible color, the first number denotes the tone or lightness or darkness and second number denotes the saturation of color.
The tone and saturation scale is based on number system thus 0 denotes colorless or white, 1 denotes extremely light, 2 very light, 3 light, 4 medium light, 5 medium, 6 medium dark, and so on.
Tone & Saturation
denotes colorless or white
denotes extremely light
and so on
Some examples of how color code is given to a tanzanite are as follows:
- vb1 or vBgr is violetish blue which shows grayish overtones
- vb2 or vBslgr is violetish blue which shows slightly grayish overtones
- vb3 or vBvslgr is violetish blue which shows very slightly grayish overtones
- vB4 or vBmst is violetish blue which shows slightly strong saturation of hue
- vB5 or vBst is violetish-blue which shows strong saturation of hue
- vB6 or vBv is violetish blue which shows vivid saturation of hue
Thus if you properly understand how tanzanite is graded to decide its quality, it will be helpful for you to buy this exquisitely precious and the most beautiful gemstone for your collection or as an investment.
Expert Advice on Buying Rare Gem
© 2011 Mirjan Stojanovic