Professional Jeweler Archive: Korean Heat and Pressure

December 2003


Korean Heat & Pressure

Another big company now produces HPHT-treated natural gem diamonds

Taking a leap from its usual products, a South Korean cable manufacturer is positioning itself to become your new diamond supplier. The company, Iljin, manufactures metals and communication cables and also produces synthetic industrial diamonds. Iljin describes itself as one of three major manufacturers of high-quality synthetic industrial diamonds, after De Beers and General Electric Co. Now Iljin has a new venture using natural gem diamonds.

U.S. Debut

At the summer JA Show in New York City, Iljin introduced its Nouv line of high-temperature/high-pressure treated natural diamonds. You guessed it: the same presses that cook up synthetic diamonds can be used to treat natural goods. Iljin calls it a “proprietary rebirth process” that permanently “restores” the fancy colors a diamond would have had if nature had acted a little differently.

Iljin focuses on nitrogen-containing Type I diamonds to produce fancy yellow, orange and green stones. The company says these diamonds will be marketed only through reputable jewelers worldwide. Iljin official Woo Young Choi says the company is having its entire production of HPHT diamonds graded and laser-inscribed by EGL USA.

Iljin in Action

In the past few years, HPHT processes have been widely reported and investigated, as have many HPHT processes and identifying techniques involving Type II and Type I diamonds. Professional Jeweler viewed a selection of Iljin’s diamonds and looked for treatment characteristics like those reported in other studies.

Microscopy showed the graphitization of internal inclusions in Iljin’s treated diamonds, which is typical with HPHT processing. During the HPHT process, diamonds are subjected to temperatures from 2200&Mac251;C to 2300&Mac251;C and pressure from 60 to 80 kilobars. EGL USA’s researchers say this can cause graphitization in a diamond’s crystal inclusions or along a stress fracture.

Researchers at EGL USA also described frosty-appearing fractures that reach the surfaces of HPHT stones – further evidence of the high temperature used in the process. We observed this in one stone from Iljin.

Other observations include the intense fluorescence of Iljin’s neon green diamonds, also characteristic of HPHT, in which H3 centers (or carbon vacancies) are present in nitrogen-containing Type IaA/B diamond rough.

  • Iljin Diamond Co. Ltd., Seoul, South Korea; (82-2) 707-9737,

– by Robert Weldon, G.G.

Iljin’s Nouv brand diamonds show a typical range of colors, including yellow, orange yellow, orange, light brown and a strongly luminescent (due to fluorescence) neon green.

Photo by Robert Weldon.

Internal discoidal stress fractures and graphitized sections (the dark areas) are typical inclusions found in HPHT-treated diamonds. Photo by Robert Weldon.
One Iljin-treated diamond exhibits frosty-looking stress fractures along its girdle. These inclusions are also typical of HPHT processes. Photo by Robert Weldon.

Copyright © 2003 by Bond Communications