The latest technological breakthrough in gem enhancement – the “Yehuda” treatment for diamonds is sure to spark controversy throughout the industry, as these enhanced stones filter into the marketplace and cause concern over their disclosure and evaluation.
The treatment developed by inventor Zvi Yehuda of Israel is not unlike modern emerald oiling in that a foreign substance is forced into surface fractures to stabilize and enhance appearance. In emerald, the material is an oil, but in the Yehuda process, a glass-like substance is introduced under extreme pressure. Since the substance replaces air within the stone, the inclusion becomes much less visible to the naked eye, – and virtually invisible if its refractive index approximates its host
Although some secrecy surrounds the process itself, the effect can be readily observed by the trained gemologist.
Microscopic examination may reveal the flow structure, trapped bubbles and an overall crackled texture, or characteristic flash. The filler’s color may also be darker than the host diamond.
These factors cause great concern to those involved in the evaluation of such diamonds. Stones tested by both the Gemological Institute of America (GIA) and American
Gemological Laboratories (AGL) showed many graded higher in clarity when filled. Should appraisers grade on the treated appearance or try to “backtrack” to the prior condition? If the filled material imparts color (tests reveal commonly one grade lower than when untreated) how do we judge the new product?
In fact, color causes its own grading problems. The nature of the process and type of inclusions being altered often creates a “directional” color in the diamond. A single specimen appears to grade differently depending upon the angle of observation.
What the “big guys” say
The stance of the GIA is to currently refuse evaluation of Yehuda-treated diamonds. AGL advocates the development of a system to grade such stones realizing that conventional techniques are stretched to the limit and require modification to accommodate these stones.
Jewelers have their own problems. Although Yehuda-treated diamonds are accompanied by a disclosed pledge for the dealer when returned from their treatment facility, Diascience, INC. in new York when the diamonds change hands, the disclosure aspect often gets lost in the shuffle and may be sold as untreated. A retail customer not made aware of this fact has recourse when the truth is known and the reflection is certainly upon the jeweler, not their suppliers. And, the unaware bench jeweler repairing an article with such a treated diamond may unknowingly release the filler material through the heat from their torch, returning the diamond to its original condition. What will the diamond’s owner say when it is returned to them?
Since the Northwest market is not yet familiar with these diamonds, this is the time to investigate the issues raised and form a basis for evaluation. As the major appraiser of fine jewelry in this market, NGL is in the process of forming a policy concerning these diamonds. We welcome your opinions on this issue and will publish some of those comments as well as our findings in future issues.