June 23, 1999
Gübelin Lab Introduces Theory on GE Process
After studying diamonds that underwent General Electric's diamond process, Gübelin
Laboratory director Christopher Smith says "If the process is as we suspect, then it should be disclosed as a treatment."
In March this year, Lazare Kaplan International and its subsidiary Pegasus Overseas Ltd. announced they would sell diamonds that had undergone an "undetectable process," developed by GE and said to dramatically enhance color and brilliance. LKI said it didn't need to disclose the process because it was not a traditional diamond treatment such as irradiation, coating or infilling. (Read related story.)
Smith studied several of the GE diamonds submitted to the Gübelin lab in Lucerne, Switzerland. He told Professional Jeweler the process probably involves controlled annealing (heating) of the diamonds to heal plastic deformations in certain diamonds. There may be additional reactions taking place within the diamond as well, however, this does not appear to involve the aggregation of nitrogen or the diffusion of nitrogen out of the stone, as earlier theories in the trade proposed.
Plastic deformations are color-causing mechanisms in certain diamonds with natural brown, pink or purple colors that may also be influenced by impurities, Smith says. Plastic deformations are defects in the crystal structure that occur when pressure causes a shift in the crystal lattices or growth planes of diamonds.
"We have observed certain characteristics which may suggest that some of the GE-treated diamonds may be detectable," he says. "In these stones (which were all Type IIa), we observed lamellar strain patterns that are not consistent with natural colorless Type IIa diamonds. They are reminiscent of strain patterns observed in brown diamonds." His findings suggest these patterns may provide a clue the diamonds have undergone the GE process.
"While the quantities of these diamonds that are hitting the market is small, it is important to keep in mind it's hitting an important segment of the market the higher colors," Smith says. Sample diamonds sent to the lab were all D or E in color and at least VS1 in clarity. He cautions, however, that his study sample was small and may not represent all diamonds processed by GE.
Separately, another major laboratory, which prefers not to be identified, confirms it subjected Type IIa diamonds to the process described by Smith. It was able to improve the color grade of the diamonds it processed. In addition, the Gemological Institute of America will announce a trade update on its research on the GE process this afternoon.
- by Robert Weldon, G.G.