September 4, 1987: The Rapaport Diamond Report published news of a process developed by Israeli diamond cutter and inventor Zvi Yehuda to fill the cracks and fractures of diamonds with a clear, colorless substance. The bulletin reported a “startling” degree of clarity enhancement and raised the issue of disclosure:

Using a secret ingredient, that is introduced at extremely high pressure (50 atmospheres) and temperature (400°C), Mr. Yehuda is able to hide cracks in a diamond. His method is far more difficult to discern. Most dealers using only a loupe may not be able to identify the treated stones.

In the current environment we must take on the additional responsibility of speaking out and disclosing defects in the merchandise we sell. It is the responsibility of the seller to fully disclose any diamond treatment. (“Diamond Treatment—Buyers Beware!” Rapaport Diamond Report, Vol. 10, No. 32, p. 8)

Although Yehuda had developed this treatment process in 1982, fracture-filled diamonds were first observed in January 1987, by the Central Gem Laboratory in Japan and the GIA Gem Trade Laboratory (GIA GTL). In the months leading up to the Rapaport bulletin, GIA GTL began to encounter a number of diamonds that appeared to have been treated in this manner.

The Rapaport piece generated significant concern about the identification of these fracture-filled diamonds, and about their durability during normal jewelry repair procedures such as heating with a torch or prong retipping. As the diamond industry attempted to deal with these concerns, and with the issue of properly disclosing fracture filling to customers, GIA researchers launched an effort to educate the industry on the first major diamond treatment.

The result was a series of G&G articles on fracture-filled diamonds, beginning with John I. Koivula et al.’s “The Characteristics and Identification of Filled Diamonds” (Summer 1989, pp. 68–83). This article reported that the presence of the filling material could be readily detected using a standard binocular gemological microscope. The key diagnostic features were identified as orange and blue “flash effects,” flow structures, and flattened, trapped gas bubbles in the filled areas of these diamonds. The study used chemical and other analyses to determine that the filling material was a type of glass.

Five years later, fracture-filled diamonds had become increasingly prevalent in the market, and new players had entered the field. Robert C. Kammerling et al.’s follow-up article, “An Update on Filled Diamonds: Identification and Durability” (Fall 1994, pp. 142–177), examined not only Yehuda fracture-filled diamonds, but also products from Koss & Schechter Diamonds and Goldman Oved Diamond Co. The study determined that the fracture-filling processes of all three companies could improve the apparent clarity of a diamond by one or sometimes two grades. The flash effect remained the most distinctive and consistent identifying characteristic, and each company’s product remained susceptible to damage by direct heating and repolishing.

The following year, Shane F. McClure and Robert C. Kammerling published “A Visual Guide to the Identification of Filled Diamonds” (Summer 1995, pp. 114–119). This article placed the information in a color chart illustrating the key identifying features seen in filled diamonds. Also provided were features observed in unfilled fractures that might be confused with the features found in filled diamonds.

After the mid-1990s, several years passed with few new developments in fracture-filled diamonds. That changed in early 2000, when Oved Diamond Company announced their intention to market diamonds filled with a new glass formulation (XL-21). James E. Shigley et al. responded with “New Filling Material for Diamonds from Oved Diamond Company: A Preliminary Study,” Summer 2000 (pp. 147–153). The article concluded that the new Oved glass-filled diamonds were readily identifiable by the intense flash-effect colors exhibited, but that they were more stable to direct heating with a torch. Still, some damage to the filler was observed in some of these diamonds during prong retipping.

Stuart Overlin