“Diamond Treatments and Synthetics; Current Hot Issues in Colored Stones”

Matthew Hall

This month’s DC GIA meeting featured Matthew Hall, Manager of Identification Services in GIA’s New York laboratory, and Donna Beaton, supervisor of Colored Stone Services at GIA New York.

This fascinating dual lecture not only addressed up-to-date information on diamond as well as colored gemstone treatments, but also GIA’s new emphasis on the laboratory services they provide above and beyond education.

Matthew Hall began the evening by addressing the issue of diamond treatments and synthetics.
He reviewed the different types of diamonds and the impurities that create color. He then addressed the three main diamond treatments on the market—HPHT, irradiation and annealing, and diamond coating—and discussed the various inclusions that assist with identifying these treatments.
Type II diamonds are susceptible to HPHT treatment. The newest diamond coating on the market are “Serenity Coated Diamonds”, which are a silicate based, multi-layered coating on the pavilion; different from earlier coatings which were calcium fluoride doped with gold.

Mr. Hall then reviewed the current synthetic diamonds on the market, the HPHT and the CVD grown. All CVD are Type IIa, nitrogen doped. The earlier CVD diamonds tended to be small, a distinct brown and included; now they are colorless with high clarity and larger in size.
Fancy colors such as orange and pink have been added to their line up. He offered slides illustrating various inclusions that assist with identifying these synthetic diamonds, and discussed GIA’s new service, a Diamond Type letter that identifies a diamond’s type from Ia to IIb. Given the Type II’s use for both treatment and synthesis, this could be a useful letter for our field.

Donna Beaton

Donna Beaton rounded out the evening by discussing three hot issues in colored gemstones—the irradiation of colored gemstones (namely blue topaz), lead glass filling of ruby, and beryllium treatment of corundum.

Lead glass filling is now being divided into 3 cases of increasing filling, from Case A to Case C. Case C is the most extreme lead glass filling where the “gemstone” is basically an assemblage of pieces of gemstone bonded by lead glass.

She points out that the GIA Lab has seen not only lead glass filled rubies but also sapphires; with rubies, the blue flash effect, milkiness and bubbles give the filling away.
She also addressed beryllium treatment of corundum, in reference to the abundance of padparadscha sapphires on the market, and pointed out that the treatment is nearly entirely throughout the gemstone, so the orange zoning test is no longer as conclusive as it once was.
She introduced the GIA Laboratory’s myriad of new testing, identification and grading services, from basic to premier, along with a price list. Please contact labservice@gia.edu for more information.

Many thanks to our guest speakers for an informative and entertaining lecture! If you were not able to join us, you missed invaluable slides that help gemologists identify these new treatments and synthetic gemstones.

Summary by Etta M. Saunders, PhD, GG, ISA AM

Meeting Photos by Melanie Marts – GG