The Gemological Institute of America’s GemFest Basel addressed a host of hot topics:
Dr. James Shigley, GIA director of research, led off with some good news: Synthetic diamonds are no longer a concern for the jewelry industry.
Because of the way synthetic diamonds are grown in a laboratory, Shigley said, their growth process produces a distinct color-zoning feature that gives the stones identifying characteristics.
A greater concern is continued HPHT treatment of natural stones. The treatment used to be confined to Type II diamonds but now includes Type I diamonds, the type that accounts for 95% of the diamond market. As HPHT expands, Shigley said GIA is continually updating its research to keep up.
Shane McClure, GIA’s West Coast director of identification services, said a new fracture-filling treatment, first seen late last year in some rubies from Madagascar, is coming on to the market.
Opaque to translucent, these highly fractured rubies are being infused with leaded glass, which has a very high refractive index and blends into the stone to make the inclusions less visible and the stone more salable. Under magnification, one can see huge networks of fractures in these stones. The treatment is reasonably durable against normal processes like mounting and retipping, but when exposed to a caustic solution such as that used for pickling, it can remove or harm the glass filling.
GIA president Bill Boyajian noted that GIA’s forthcoming cut-grade system focuses on the interrelation of proportions to one another, not on any one set of specific proportions. This, says Boyajian, allows cutters to cater to different market tastes without penalizing a market by implying its preferred cut is a lesser cut.
Boyajian also announced the nomenclature to be used to describe cut: Excellent, Very Good, Good, Fair, and Poor. He said GIA expects the bulk of stones submitted for grading will fall into the top three categories, but that the bottom two may be needed from time to time. The cut-grading system will apply only to round brilliants, D to Z color, flawless to I3. It will not apply to modified round brilliants or to fancy cuts or colors.