The JAA has defended one of its members, ADGL (Australian Diamond Grading Laboratory), against industry rumours about the laboratory’s incorrect grading of a pink coated diamond as a natural pink diamond.
In a media release issued on February 13, JAA president Ian Hadassin said it been “widely publicised” that the ADGL had incorrectly graded the diamond, which was later correctly graded by DCLA (Diamond Certification Laboratory of Australia).
“Some industry participants have gone out of their way to make sure that the trade in general, and ADGL customers in particular, are aware that ADGL was the laboratory involved” in the incorrect grading,” he said.
“It is a great pity that they did not consider contacting ADGL direct to discuss the issues involved.”
He added that although the incorrect grading was a serious matter the incident needed to be considered in a “balanced, objective manner”.
“Industry experts have advised that it is extremely difficult to tell if a natural diamond has been coated, particularly if the coating has been smoothly applied. The Diamond Sure testing machine that most laboratories have will not pick it up,” he said.
“In fact the only conclusive way of finding out is by using a test that results in the destruction of the stone. There is no other non-destructive way of determining whether a diamond is coated other than looking at the stone through a loupe or microscope and seeing if there are any blotchy areas or if the coating is missing on the facet joints.”
“It has become apparent that, at some stage between the stone being graded by ADGL and the time it was graded by DCLA the stone was heated or polished and this resulted in the stone losing most of its pink colouring and some of the coating itself.
“This explains why the stone that ADGL certified was a bright pink and the stone that DCLA examined contained very little pink colour. It also explains why it was easy to see that the stone was ‘blotchy’ and hence coated.”
Hadassin said that the ADGL have given the JAA a written undertaking that it will no longer grade coloured diamonds except where they are high-pressure high-temperature treated.
He stressed that ADGL’s competence to certify white diamonds had not been called into question
* Photograph of the coated pink diamond supplied by DCLA.