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GIA Announces Refinements for Fancy Colors
By: John M. King, James E. Shigley and Robert C. Kammerling
GIA Gem Trade Laboratory, Gemological Institute of America
The GIA Gem Trade Laboratory (GIA GTL) has made important refinements to its system for color grading colored diamonds. To help disseminate this information to the trade, the following report has been developed from the article "color Grading of colored Diamonds in the GIA Gem Trade Laboratory," by John M. King, Thomas M. Moses, James E. Shigley, and Yan Liu. It was published in the winter 1994 issue of Gems & Gemology (Vol. 30, No. 4, pp. 220-242), the quarterly journal of the Gemological Institute of America. Readers are encouraged to obtain and read the original article on this subject. Additional topics in the article include a brief history of diamond color grading at GIA GTL, some basic color science concepts, GIA GTL color terminology for colored diamonds, and a note on some special situations encountered in describing colored diamonds.
One of the primary goals of the GIA Gem Trade Laboratory is to support the diamond industry through services that help protect the trade and facilitate business. Particularly significant to the trade today are colored diamonds. Two important concerns with these diamonds are their color origin--that is, whether their color is natural or laboratory treated--and their color description or grade. As part of its ongoing research and development efforts in the area of color, GIA GTL has recently announced improvements to its system for color grading fancy color diamonds. These improvements represent refinements to the long- established system which in its essentials remains unchanged in concept and application. So that members of the trade could better understand these refinements, GIA GTL decided to explain the concepts on which the color grading system is based through the article cited above.
Why the Refinements? Until fairly recently, colored diamonds were encountered infrequently in GIA GTL, as in the trade. Today, however, increasing numbers, and a broader variety of colors, are seen. One reason for this is the Argyle deposit in Western Australia, which has brought many more colored diamonds to the marketplace during the last decade. Some of these diamonds, such as the intensely colored pinks, command high prices. In addition, recent auction sales have spurred interest in colored diamonds--and these well-publicized sales have generated a number of articles in the trade press. Recognizing that a system to communicate the colors of these diamonds clearly and consistently is vital for effective commerce, GIA GTL undertook a comprehensive re-evaluation of its system.
Importance of Standard Procedures Clearly, standard procedures must be established and followed if colored diamonds are to be graded effectively and consistently. In the GIA GTL system, color science methodology is used as the basis for these procedures. At the same time, sensitivity must be maintained to both the unique properties of colored diamonds and GIA GTL's 40-year history of grading these stones. Among the factors that must be taken into consideration during color grading are the following:
* A consistent, standard source of light with known illumination characteristics
* An appropriate visual environment for grading
* The "geometry" between the positions of the light source, the diamond, and the observer
* The use of standard color reference materials for color comparison
* The normalcy of the color vision of the observer * The language used to describe color
* The relationships between the chosen color terms
To address these factors, GIA GTL uses a standard light source, viewing environment, and viewing "geometry"; in addition, all graders are tested to establish that their color vision is "normal." For the actual color grading of colored diamonds, we follow a basic three-step procedure: First, we determine the face-up color to be described (referred to as the "characteristic" color). Next, we locate the position of that color in relation to other colors by using known reference comparators. Last, we select appropriate terminology to describe that color. This process uses color grading concepts similar to those applied when grading near-colorless to light yellow (or brown) diamonds on the D to Z color scale; for example, in most cases boundaries are marked with diamond master stones, colour terms are applied to ranges of color appearances, and controlled side-by-side visual comparisons are made. Unlike D to Z grading where stones are judged primarily in the table-down position to establish the relative absence of color, the fancy color grading system judges the relative presence of color in the face-up position.
New Fancy Grades
To strengthen the already-established system, GIA GTL has expanded the use of its Fancy-grade terms to all hues and has introduced two new Fancy-grade terms--Fancy Deep and Fancy Vivid--to better address areas of strong color. The other GIA GTL Fancy grade terms are: Faint, Very Light, Light, Fancy Light, Fancy, Fancy Dark and Fancy Intense. Fancy Deep is the term used to represent moderate to strong colors that are dark in appearance. Fancy Vivid represents hues that are medium to light but very saturated.
The locations of boundaries between different Fancy grade terms vary depending on the diamond's hue. For example, a relatively rare diamond color such as blue, which typically occurs in lower saturations, is assigned certain "Fancy" grades at lower saturation levels than a color such as yellow, which usually occurs in higher saturations.
We will update these pages with news about important changes within the diamond Industry. The Diamond industry is evolving. We have had the creation of a GIA Cut Grade and a change to the Fancy Color Diamond grading system as well. Many more important update will surely follow. We hope, we can keep you abreast of some of the changes.
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