May 23, 2002
Sapphire Treatment Source Revealed
Lab technicians at Swarovski Co., Wattens, Austria, have confirmed why the element beryllium is evident in sapphires exhibiting dramatic color changes. These sapphires roiled gem markets because no one knew conclusively how the color change happened.
Swarovski says the sapphires, from Madagascar and Africa, have been heat-treated with the gem chrysoberyl, which contains beryllium. The Swarovski technicians heated sapphire and chrysoberyl together in five tests that confirmed the connection when the sapphires were transformed into the newly observed colors. Swarovski performed the tests after its rough gem buyer Yianni Melas noticed that sapphires parcels he purchased in Madagascar frequently contained water-worn crystal fragments of chrysoberyl.
"The beryllium obviously comes from the chrysoberyl," says Shane McClure, who has been studying the treated sapphires at the Gemological Institute of America. Swarovski shared its findings with GIA, which will issue a new statement shortly acknowledging the new information. "While the reason why this happens is not yet completely understood, there is no doubt it is a form of diffusion. That's now proven," says McClure.
GIA and other labs issued a statement several months ago describing the newly treated gems. They avoided using the term "diffusion" to describe the new treatment, because the color change effects differed from diffusion treatments previously seen. McClure says beryllium diffuses much faster through corundum than other elements diffused in sapphires, such as titanium. This may account for why the new gemstones feature diffused color, which in many cases goes through the whole stone instead of being confined to a surface layer as previously seen.
by Robert Weldon, G.G.