Scientists at the Gemological Institute of America (GIA) in New York have discovered a never-before-seen spinel treatment by nickel diffusion. 

The New York team examined supposedly cobalt-diffused spinels from a parcel of gems acquired for research by GIA Bangkok. Researchers detected high concentrations of nickel, consistent with diffusion treatment. The treatment with nickel, not seen before by GIA or reported in gemmological literature, caused the development of a blue-to-green colour in pale-coloured spinel and was accompanied by artificial healing of fractures resulting from the heating process.

“The detection of this new treatment underscores the vital importance of GIA’s independent research to protect consumers and ensure that they, and the global gem and jewellery trade, have confidence in their purchases,” said Susan Jacques, GIA president and CEO. 

Using advanced spectroscopic equipment, GIA researchers discovered indications of nickel-related absorption in natural spinel. Other key indicators of the nickel absorption treatment are colour concentration at facet junctions, photoluminescence spectra indicating heat treatment and abnormally high amounts of nickel. 

“Nickel-diffused spinel has not been seen before by GIA,” said Shane McClure, global director of coloured stone services at GIA’s world headquarters in Carlsbad, California. “Anyone examining spinel in this colour range showing evidence of heat treatment should consider the possibility of nickel diffusion.”

GIA first reported on spinel treated by cobalt diffusion in 2015. Examination for the treatment, which yields a vibrant blue hue, is part of GIA’s gemmological service for spinel.