What is coated Tanzanite?
In May 2008, two major New York City gem labs – the American Gem Trade Association Gemological Testing Center (AGTA GTC) and American Gemological Laboratories (AGL)- received a number of faceted tanzanite samples that were determined to be coated. The cobalt coating was not immediately obvious but careful examination with a microscope and in immersion provided clear indications of the coating. The majority of the tanzanite sample was comprised of smaller calibrated pale tanzanite where coating was used in order to give them the appearance of fine stones.
