Roskin Gem News Report

New Spinel Treatment: Nickel Diffusion

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

GIA Researchers Identify New Spinel Treatment

The press release announcing this discovery was highlighted by a statement from GIA president and CEO Susan Jacques, who said, “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 jewelry trade, have confidence in their purchases. 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 gemology, 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.”

It also gives us all fair wirning to start looking for this treatment.

GIA Press Release: New Spinel Treatment

GIA Researchers Identify New Spinel Treatment
Nickel diffusion discovered in research parcel

CARLSBAD, Calif. – Feb. 14, 2023 – 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 gemological literature, caused the development of a blue-to-green color in pale-colored 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 jewelry 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 gemology, 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; “Color Modification of Spinel by Nickel (Ni) Diffusion: A New Treatment in the Gem Market” 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 color 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 colored stone services at GIA’s world headquarters in Carlsbad, Calif. “Anyone examining spinel in this color range showing evidence of heat treatment should consider the possibility of nickel diffusion.”

“One of our skilled gemologists, 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 gemological service for spinel.

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

Links to GIA research articles referenced above:

Color Modification of Spinel by Nickel (Ni) Diffusion: A New Treatment in the Gem Market (2023)

GIA Lab Reports on a New Cobalt Diffusion Treatment of Natural Spinel (2015)

A Discussion with Aaron Palke

So we reached out to GIA’s Aaron Palke to discuss a few details about this discovery that we thought might be helpful. Our first question, “Why Nickel?” We have seen Titanium and Iron diffusion, Beryllium Diffusion, and even Cobalt Diffusion, but nickel? Does nickel color any natural gemstones?

“It’s unclear why they diffused with nickel,” says Palke. “It is likely they were experimenting, and nickel seemed to work. We’re planning more experiments to try to understand this better.” Palke noted that chrysoprase is nickel colored chalcedony, or rather “chalcedony colored by microinclusions of nickel rich silicate minerals.” And some rare diamonds can have color caused by nickel as well.

Thinking back to other diffusion treatments, many of us have seen the dark facet junctions of a titanium and iron diffusion treated sapphire. So can we see the concentration of nickel diffusion similar to Ti and Fe diffusion?

Palke noted that, “of the cases we’ve seen so far, you could see color concentration at facet junctions, but it’s not as obvious as typical Ti diffused sapphire.”

We noticed from the G&G article that the nickel diffusion also includes lots of other elements, like Beryllium and Lithium and Iron … Is this just a mixture compound that anyone in the heating business can use on any stone to see what works?

“Some of the elements,” says Palke, “like lithium, could have been part of fluxing agents that were likely used to partially heal fractures during the heating process.”

We asked whether or not there were any nickel treated spinels in Tucson just a week ago. Palke didn’t think so.

“I didn’t see any. The [samples we have] were bought in the marketplace in Bangkok, so they could be expected to be circulating. We’ve also not seen them submitted to the lab for services,” says Palke.

Last question: Could a desktop gemologist misidentify it as Cobalt Spinel – seeing a cobalt spectrum – if they’re not careful, or is there just too little of it to make the call?

“A desktop gemologist with no UV-Vis and no XRF should turn to microscopy,” suggests Palke. “Evidence of heat can be seen in the artificially healed fractures with residues which could indicate diffusion treatment.”

Palke gives us another indication:

“The color of nickel diffused spinel tends to be different than typical cobalt diffused spinel, with more green modifier even in the stones with more blue color. Gemologists should also be aware that there is some cobalt diffused material circulating which doesn’t show prominent color concentrations at facet junctions, but which should show evidence of heat in a microscope.”

The Desk Gemologist with Advanced Instrumentation

We did speak to Alberto Scarani, co-owner of MagiLabs Gemological Instruments, who believes it shouldn’t be a problem for the GemmoRaman and GemmoSphere (portable advanced gemological instruments) to detect nickel diffusion, now that we know what to look for. He confirmed that while he has not yet seen any Ni diffused spinel, from reading through the literature, UV-Vis spectra and PL reactions should be easy to get with little or no problems using the GemmoSphere and GemmoRaman. “More specifically, to get the 597 and 639 nm peaks [indicating nickel in tetrahedral coordination], and the 369 nm and 381 nm peaks [indicating nickel in octahedral coordination as described in the GIA research paper] should be fairly simple for the GemmoSphere.”


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