CHEAP, low-grade diamonds could easily be disguised as high-quality gems in a
process developed by South African diamond giant De Beers. But De Beers won’t be
selling the diamonds—it will use the phoney gems to find new ways for
jewellers to spot fakes, as rapid advances by counterfeiters make it more
difficult to identify them.
“I can categorically assure you that no treated low grade diamonds leave our
labs,” James Evans Lombe of De Beers told 91av. But some
counterfeiters are already using a similar technique, he says.
“So far the diamond trade has been lucky,” says Stephen Kennedy, director of
the Gemmological Association’s test lab in London. For now, dealers can easily
spot fakes with a standard lens. But this could soon change. “The average
diamond dealer does not have the equipment needed to recognise what’s now
feasible,” says Kennedy.
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The new, patented technique can transform second-grade diamonds, which have a
distinctive brown tinge caused by structural deformations on their surface. It
uses an annealing process to “flatten out” the deformations and the tinges they
cause, making the sub-standard gems look like rarer and more valuable
colourless, pink or blue stones.
To achieve this deception the brown stones are embedded in loose crystals of
a metal halide salt such as potassium bromide or sodium chloride—depending
on the colour you want. This is then placed in a cylinder made of graphite and
pressurised at 85,000 bars. An electric current passed through the graphite
heats the contents to more than 2000 °C for several hours, after which it is
allowed to cool (see Diagram).
Under high pressure and temperature, the salts exert an even spread of
pressure on the surface of the stones, ironing out the deformations that cause
the diamonds to exhibit a brown tinge. Afterwards, the salts are dissolved in
hot water and washed away, leaving an untinged stone.
“The new processes build on the technology used for making artificial
diamonds,” says Kennedy. Only a few companies can do it, such as General
Electric in the US and De Beers, he says. “So far we think all treated stones
have been marked as such.”
But he warns that Russia now has the technology to improve stones. “We don’t
know whether or not they are using it,” he says. “Human nature being what it is,
the trade had better be prepared.”
