Feb 15, 2023

GIA Identifies New Spinel Diffusion Treatment

Suite of faceted nickel-diffused spinel (0.674-1.009 ct) showing the range of colour from blue to bluish green. Photo by Aaron Palke and Diego Sanchez, GIA

Scientists at the GIA laboratory in New York City recently discovered spinel treated by nickel diffusion in a parcel of gems acquired for research purposes by the GIA research team in Bangkok.

In examining the supposedly cobalt-diffused spinels, GIA researchers discovered 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.

“This discovery is the result of our very important and comprehensive research program, in which GIA invests millions of dollars each year. We have an exceptional team of experts and scientists in gemmology, geology, physics, chemistry and other disciplines using very sophisticated instrumentation. This is what enables us to detect new, undisclosed treatments which, if undetected, can deceive both the trade and consumers.”

Gems & Gemology, GIA’s quarterly professional journal, recently published the research online; it will appear in the Spring 2023 print edition of the journal.

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.”

“One of our skilled gemmologists, Abadie Ludlam, suggested that we look closely at the cobalt-treated spinel,” said GIA research scientist Dr. Mike Jollands, the Lead Author of the article. “Our analysis showed barely detectable cobalt and revealed previously unseen and highly elevated nickel concentrations in the spinel.”

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.