I recently wrote to Dr. James Shigley, Director of Research at the Gemological Institute of America, to see if any progress had been made on research in the field of diamond material transparency.  The reply was, of course, highly technical in nature, but I feel that my customers should be made aware of the importance of the information expressed in his letter, excerpts of which are printed below.   -----Steve Martin, GIA Graduate Gemologist, MBA, BSEE. (If you have any technical questions on this subject, please call me and I will be happy to answer them).

"Natural diamonds often have a complex history which included periods of both growth and dissolution of the rough crystals during their long residence time in the earth.  During growth, they can also incorporate small amounts of impurity elements.  These physical and/or chemical variations can be manifest in growth imperfections or "graining" that can DETRACT FROM THE CLARITY OR TRANSPARENCY OF A POLISHED DIAMOND. Beyond the visual observations of graining in various patterns and appearances, and the related observations of anomalous birefringence patterns when the diamond is viewed with the microscope using cross-polarizing filters,  WE DO NOT HAVE MORE PRECISE WAYS TO DOCUMENT TRANSPARENCY VARIATIONS WITH A DIAMOND."

Essentially what Dr. Shigley is saying is that the diamond material itself can vary from stone to stone, and this will affect the brilliance and beauty of the diamond.  In other words, even if two diamonds theoretically have exactly the same measurements, they can look entirely different. As trained gemologists, my staff and I use various techniques to select diamonds of the highest quality "crystal" material, and buy stones from only the finest cutters who  specialize in these types of diamonds.  As noted in his letter, because this characteristic cannot yet be measured, there is nothing on a diamond certificate that will indicate if a diamond is cut from sub-par material.

For this reason, diamond buyers should always consult a trained and experienced GIA Graduate Gemologist. (See #10).

Return to continue reading "The Ten Biggest Mistake Diamond Buyers Make."

Technical Note:  The specific gravity of a diamond is usually given as 3.52 (that is, 3.52 times as heavy as an equal volume of water), but it does indeed vary from 3.50 to 3.524.  This differential in conjunction with variations in facet angles explains why some stones are beautiful, bright, and sharp, while others are weak in appearance.  (Source: "Diamonds", Crown Publishing, p.194.)