Grading Natural Color Diamonds

While evaluated Natural Color Diamonds, the gemologist directly look from the “face up” position, through the top of the diamond. There are three parameter that used by gemologist  the Gemological Institute of America (GIA) and the International Gemological Institute (IGI) to describe color of the fancy diamonds :

First : The basic hue colors of the fancy diamonds.It refers to the dominant color of the diamonds, such as brown, green, blue, pink, etc. Also, There can be tints (modifiers), which will causing more than one hue to the stone. For instance, a purplish-pink diamond indicates a stone with principal pink hue and purplish tints.  Pure color which is contain no tints will be called pure primary tints.

Second, their intensity. Both color characteristics form the basis for determining a fancy colored diamond’s worth. Usually, the more intense the color, the rarer and more expensive the diamond will be

Color Saturation

Color Saturation describes the strength or intensity of the hue or main color. The saturation of light toned diamonds can vary from a pastel to vivid and intense. Darker diamonds will range from dark to deep in description.

Color Tone

Color Tone refers to how much lightness or darkness a stone appears to retain even when illuminated. The range, obviously, is from light or very light, to dark or very dark.

When grading fancy diamonds, the GIA uses nine grade categories:

1.Faint

2.Very Light

3.Light

4.Fancy Light

5.Fancy

6.Fancy Dark

7.Fancy Intense

8.Fancy Deep

9.Fancy Vivid

It’s interesting to note, that a secondary undertone that enhances the color of a diamond is considered a plus, while a secondary undertone that detracts from the color is a negative.

How Color Is Graded

Natural Color Diamonds are graded by gemological laboratories in very high-tech environments under controlled lighting environments similar to natural daylight. First, diamonds are tested for treatment, synthetic additions or alterations to ensure authenticity. Most laboratories will scan diamonds with a spectroscope to compare readings with their historical data and utilize High-Pressure-High-Temperature (HPHT, the most common process used to enhance the color of diamonds) detection and other proprietary equipment. Gemologists will also use comparison stones and proprietary color chips to compare two diamonds to each other. Though the face-up appearance is ultimately what determines the diamond color, stones are evaluated from other angles as well.

Grading Reports
Two types of reports are available:
(1) Full Certificates provide full details about a stone including clarity, symmetry and polish, and (2) Color-only certificates that provide color grading for natural fancy colored diamonds.

“Grading the color of the colored diamond is one of the greatest challenges in gemology… the challenge has been to apply scientific, yet practical, time-tested standards to such rarities of nature…” G&G (Gems & Gemmology), Color Grading of Colored Diamonds in the GIA Gem Trade Laboratory

Fancy Color Diamonds

“Fancy color diamonds” are a very rare and expensive type of diamond. A fancy diamond can range in color, from various shades of yellow to red, pink, blue, or green. Fancy Diamonds are valuable because of their rarity, and are the only diamonds that are made more valuable because their color exceeds the GIA color scale.

Fancy color diamonds are graded based on two factors. The first is their basic hue, such as pink, yellow, blue, green, etc. The second is their intensity. Both color characteristics form the basis for determining a fancy colored diamond’s worth. Usually, the more intense the color, the rarer and more expensive the diamond will be.

When grading fancy diamonds, the GIA uses nine grade categories:

1.Faint

2.Very Light

3.Light

4.Fancy Light

5.Fancy

6.Fancy Dark

7.Fancy Intense

8.Fancy Deep

9.Fancy Vivid

It’s interesting to note, that a secondary undertone that enhances the color of a diamond is considered a plus, while a secondary undertone that detracts from the color is a negative.

Fancy Color Diamonds were found throughout the years in Australia, Brazil, Venezuela and parts of Africa where conditions are right for the development of their natural color.

January 6, 2010 - Posted by | Learn Diamond

1 Comment »

  1. I watched a video from the GIA Institute and they compare the diamonds that they’re grading against Diamonds in their database.

    In the recent GIA journal there is also talk of a ‘sister’ Hope diamond, one of the most famous fancy color diamonds known to man.

    Comment by GIA Diamonds | July 7, 2010 | Reply


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