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Diamonds with undisclosed 'sophisticated' coatings have been detected by international grading laboratories
Diamonds with undisclosed 'sophisticated' coatings have been detected by international grading laboratories

Diamond treatments continue to cause suspicion

Following the recent grading certificate recall by the GIA, another international diamond grading laboratory has reported stones with an undisclosed “sophisticated” treatment.

The Gemological Institute of America (GIA) recalled 424 diamond grading reports last month on suspicion that the certified stones had undergone an “undisclosed temporary treatment”. The treatment was believed to improve the colour of a diamond temporarily by up to three grades.

It has since been suggested that the treatment may have been a coating, although Phil Yantzer, vice president of GIA Carlsbad laboratory services, reportedly declined to remark on this theory when it was raised at an industry conference a few weeks ago.

Commenting on the recent developments, Marc Brauner, co-CEO of International Gemological Institute (IGI) Worldwide told Jeweller that undisclosed coating treatments were not a new phenomenon.

Marc Brauner, IGI Worldwide co-CEO
Marc Brauner, IGI Worldwide co-CEO

He confirmed that the laboratory had received a number of these types of submissions in the past, with one memorable incident dating back 25 years.

Brauner added that in late 2014, the IGI received diamonds from an Israeli client that proved to have been treated with a coating.

“We noticed a change of colour but at that time there was no proof since the coating was removed during our analytical processes,” he explained.

“[In a] following submission, we intercepted a 4-carat diamond, along with smaller stones, that appeared to be coated. We called in a bailiff who witnessed the colour change during our assessment, and proof of fraud was established.

“We reported this incident in a detailed letter to the Bourse in Ramat Gan. We are not aware of any action on their part, and have never even heard back from them,” he said.

Brauner also noted that a “few [other] suspicious cases” had taken place, adding that one client alleged their affected diamonds had originated from India.

“At this time we do not yet know what the exact chemical composition is of the coating or the techniques used to apply these more ‘sophisticated’ coatings to diamonds,” he said. “However, we have established various possible ways for identification.”

These methods include using a colourimeter – such as the Yehuda colourimeter – to read the colour from the ‘core’ of the stone, cleaning the diamond with alcohol or boiling the diamond in acid.

“Coating usually consists of a microscopically thin layer applied on the surface of the stone [and] the ‘improvement’ in colour can often be dramatic. This is why we systematically carry out these tests,” he said.

Close to an answer
Bill Sechos, Gem Studies Laboratory director
Bill Sechos, Gem Studies Laboratory director

Media reports suggested the colour treatment applied to the GIA’s recalled stones was the same used on the diamonds that had been identified by the IGI, however, Brauner emphasised he would not make assumptions about the findings of other laboratories.

On 31 May, industry publication JCK reported that GIA president and CEO Susan Jacques said the organisation was close to identifying the mystery treatment behind the recalled diamonds, with Yantzner adding, “We know what is being done, but we don’t know how it is being done.”

A GIA spokesperson told Jeweller there were currently no updates on this matter.

When asked if any undisclosed treated diamonds had been detected locally, Bill Sechos, director of one of Australia’s major diamond grading laboratories, Gem Studies Laboratory, responded, “At this stage we’re confident that nothing has come through here [at our lab], but we have been on the lookout since the GIA trade alert was made.”

More reading
Industry on high alert for undisclosed treated diamonds

Tuesday, 23 April, 2019 02:53am
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Peter W Beck
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